text:
OmniSharp stops working after Mono is installed.

Environment data
.NET Command Line Tools (2.1.3)

Product Information:
 Version:            2.1.3
 Commit SHA-1 hash:  a0ca411ca5

Runtime Environment:
 OS Name:     gentoo
 OS Version:
 OS Platform: Linux
 RID:         linux-x64
 Base Path:   /opt/dotnet_core/sdk/2.1.3/

Microsoft .NET Core Shared Framework Host

  Version  : 2.0.4
  Build    : 7f262f453d8c8479b9af91d34c013b3aa05bc1ff

VS Code version: 1.20.0-1516947444
C# Extension version: 1.13.1
Steps to reproduce
Install the .NET Core SDK without Mono and a fresh install of VSCode. Open up a C# project and verify that extension functionality works.
Install Mono alongside the dotnet tool. Try opening the same project in VSCode.
Install MSBuild for Mono since the OmniSharp warning suggests to do so. Try opening the same project in VSCode.
Expected  behavior
Intellisense, CodeLens, etc. works in all three scenarios. After installing MSBuild, the warning that it is not installed goes away.
Actual behavior
Intellisense, CodeLens, etc. only work in the case where .NET Core is installed without Mono or Mono MSBuild. The warning that MSBuild is not installed remains after it is installed alongside Mono.
Starting OmniSharp server at 2/2/2018, 12:25:16 AM
    Target: /home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass

OmniSharp server started wth Mono
    Path: /home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/OmniSharp.exe
    PID: 20413

[info]: OmniSharp.Stdio.Host
        Starting OmniSharp on gentoo 0.0 (x64)
[warn]: OmniSharp.MSBuild.Discovery.Providers.MonoInstanceProvider
        It looks like you have Mono 5.2.0 or greater installed but MSBuild could not be found.
Try installing MSBuild into Mono (e.g. 'sudo apt-get install msbuild') to enable better MSBuild support.
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Located 1 MSBuild instance(s)
            1: StandAlone 15.0 - "/home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/msbuild/15.0/Bin"
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        MSBUILD_EXE_PATH environment variable set to '/home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/msbuild/15.0/Bin/MSBuild.dll'
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Registered MSBuild instance: StandAlone 15.0 - "/home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/msbuild/15.0/Bin"
            MSBuildExtensionsPath = /usr/lib/mono/xbuild
            CscToolPath = /home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/msbuild/15.0/Bin/Roslyn
            CscToolExe = csc.exe
            MSBuildToolsPath = /home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/msbuild/15.0/Bin
            TargetFrameworkRootPath = /usr/lib/mono/xbuild-frameworks
[info]: OmniSharp.Cake.CakeProjectSystem
        Detecting Cake files in '/home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass'.
[info]: OmniSharp.Cake.CakeProjectSystem
        Could not find any Cake files
[info]: OmniSharp.DotNet.DotNetProjectSystem
        Initializing in /home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass
[info]: OmniSharp.DotNet.DotNetProjectSystem
        Auto package restore: False
[info]: OmniSharp.DotNet.DotNetProjectSystem
        Update workspace context
[info]: OmniSharp.DotNet.DotNetProjectSystem
        Resolving projects references
[info]: OmniSharp.MSBuild.MSBuildProjectSystem
        No solution files found in '/home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass'
[info]: OmniSharp.MSBuild.MSBuildProjectSystem
        Loading project: /home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass/free-monad-vs-typeclass.csproj
[warn]: OmniSharp.MSBuild.MSBuildProjectSystem
        Failed to load project file '/home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass/free-monad-vs-typeclass.csproj'.
/home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass/free-monad-vs-typeclass.csproj(1,1)
Microsoft.Build.Exceptions.InvalidProjectFileException: The imported project "/usr/lib/mono/xbuild/15.0/Microsoft.Common.props" was not found. Confirm that the path in the <Import> declaration is correct, and that the file exists on disk.  /opt/dotnet_core/sdk/2.1.3/Sdks/Microsoft.NET.Sdk/Sdk/Sdk.props
  at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject (System.String errorSubCategoryResourceName, Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, System.Object[] args) [0x00042] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Shared.ProjectErrorUtilities.VerifyThrowInvalidProject[T1] (System.Boolean condition, System.String errorSubCategoryResourceName, Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, T1 arg0) [0x00003] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject[T1] (Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, T1 arg0) [0x00000] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].ExpandAndLoadImportsFromUnescapedImportExpression (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement, System.String unescapedExpression, System.Boolean throwOnFileNotExistsError, System.Collections.Generic.List`1[Microsoft.Build.Construction.ProjectRootElement]& imports) [0x00517] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].ExpandAndLoadImportsFromUnescapedImportExpressionConditioned (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement, System.Collections.Generic.List`1[Microsoft.Build.Construction.ProjectRootElement]& projects, System.Boolean throwOnFileNotExistsError) [0x001a6] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].ExpandAndLoadImports (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement) [0x00024] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].EvaluateImportElement (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement) [0x00000] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].PerformDepthFirstPass (Microsoft.Build.Construction.ProjectRootElement currentProjectOrImport) [0x001dd] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].EvaluateImportElement (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement) [0x0002d] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].PerformDepthFirstPass (Microsoft.Build.Construction.ProjectRootElement currentProjectOrImport) [0x000c8] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].Evaluate (Microsoft.Build.BackEnd.Logging.ILoggingService loggingService, Microsoft.Build.Framework.BuildEventContext buildEventContext) [0x000df] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].Evaluate (Microsoft.Build.Evaluation.IEvaluatorData`4[P,I,M,D] data, Microsoft.Build.Construction.ProjectRootElement root, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, System.Int32 maxNodeCount, Microsoft.Build.Collections.PropertyDictionary`1[T] environmentProperties, Microsoft.Build.BackEnd.Logging.ILoggingService loggingService, Microsoft.Build.Evaluation.IItemFactory`2[S,T] itemFactory, Microsoft.Build.Evaluation.IToolsetProvider toolsetProvider, Microsoft.Build.Evaluation.ProjectRootElementCache projectRootElementCache, Microsoft.Build.Framework.BuildEventContext buildEventContext, Microsoft.Build.Execution.ProjectInstance projectInstanceIfAnyForDebuggerOnly, Microsoft.Build.BackEnd.SdkResolution sdkResolution) [0x00016] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Project.Reevaluate (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x0004c] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x00034] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation) [0x00000] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary () [0x00007] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Project.Initialize (System.Collections.Generic.IDictionary`2[TKey,TValue] globalProperties, System.String toolsVersion, System.String subToolsetVersion, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x000e9] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary`2[TKey,TValue] globalProperties, System.String toolsVersion, System.String subToolsetVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x0009c] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary`2[TKey,TValue] globalProperties, System.String toolsVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x00000] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary`2[TKey,TValue] globalProperties, System.String toolsVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection) [0x00000] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.ProjectCollection.LoadProject (System.String fileName, System.Collections.Generic.IDictionary`2[TKey,TValue] globalProperties, System.String toolsVersion) [0x000f5] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.ProjectCollection.LoadProject (System.String fileName, System.String toolsVersion) [0x00000] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at OmniSharp.MSBuild.ProjectFile.ProjectFileInfo.LoadProject (System.String filePath, System.String solutionDirectory, Microsoft.Extensions.Logging.ILogger logger, OmniSharp.MSBuild.Discovery.MSBuildInstance msbuildInstance, OmniSharp.MSBuild.SdksPathResolver sdksPathResolver, OmniSharp.Options.MSBuildOptions options, System.Collections.Generic.ICollection`1[T] diagnostics, System.Collections.Immutable.ImmutableArray`1[System.String]& targetFrameworks) [0x00054] in <e904597b17e840d49e5c532b51773be0>:0
  at OmniSharp.MSBuild.ProjectFile.ProjectFileInfo.Create (System.String filePath, System.String solutionDirectory, Microsoft.Extensions.Logging.ILogger logger, OmniSharp.MSBuild.Discovery.MSBuildInstance msbuildInstance, OmniSharp.MSBuild.SdksPathResolver sdksPathResolver, OmniSharp.Options.MSBuildOptions options, System.Collections.Generic.ICollection`1[T] diagnostics) [0x0000a] in <e904597b17e840d49e5c532b51773be0>:0
  at OmniSharp.MSBuild.MSBuildProjectSystem.LoadProject (System.String projectFilePath) [0x00038] in <e904597b17e840d49e5c532b51773be0>:0

[info]: OmniSharp.Script.ScriptProjectSystem
        Detecting CSX files in '/home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass'.
[info]: OmniSharp.Script.ScriptProjectSystem
        Could not find any CSX files
[info]: OmniSharp.Stdio.Host
        Invoking Workspace Options Provider: OmniSharp.Roslyn.CSharp.Services.CSharpWorkspaceOptionsProvider
[info]: OmniSharp.Stdio.Host
        Configuration finished.
[info]: OmniSharp.Stdio.Host
        Omnisharp server running using Stdio at location '/home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass' on host 18205.

Thanks for the hint. Do you know which version you were using before the upgrade? I'm on Gentoo and yesterday Portage wanted me to downgrade from 5.11 to 5.4. I masked 5.4 but maybe it's worth doing the downgrade.

With Mono 5.4 the problem indeed goes away. Not sure if this should stay around as an issue for newer Mono support or if this an upstream problem?

Note that though Intellisense starts working when Mono is downgraded to 5.4 OmniSharp still warns that MSBuild cannot be found. MSBuild is very much installed and working, in the 5.4 and 5.11 cases.

@jaccarmac Yes I was using Mono 5.4 and upgraded to 5.8.  Is there actually a Mono 5.11?  This page says the current pre-release version is 5.10.

The 5.11-pre version in Gentoo is built from a nightly tarball. I'm not aware of all the details but the ebuild is at https://github.com/gentoo/dotnet/blob/d2b1d600d2bfb2f1f715c7a89c689cf0d5c3e160/dev-lang/mono/mono-5.11.0.132_pre.ebuild

@jaccarmac: Could you let me know what folder msbuild is installed to?

Also, could you set the "omnisharp.loggingLevel" setting in VS Code to "debug" and provide your OmniSharp Log again?

$ which msbuild
/usr/bin/msbuild

But that's a shell script, the EXE is installed in /usr/share/msbuild.
With debugging on.
Starting OmniSharp server at 2/5/2018, 7:24:37 PM
    Target: /home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass

OmniSharp server started wth Mono
    Path: /home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/OmniSharp.exe
    PID: 18284

[info]: OmniSharp.Stdio.Host
        Starting OmniSharp on gentoo 0.0 (x64)
[dbug]: OmniSharp.MSBuild.Discovery.Providers.MonoInstanceProvider
        Mono MSBuild could not be used because '/usr/lib/mono/msbuild/15.0/bin/Microsoft.Build.dll' does not exist.
[warn]: OmniSharp.MSBuild.Discovery.Providers.MonoInstanceProvider
        It looks like you have Mono 5.2.0 or greater installed but MSBuild could not be found.
Try installing MSBuild into Mono (e.g. 'sudo apt-get install msbuild') to enable better MSBuild support.
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Located 1 MSBuild instance(s)
            1: StandAlone 15.0 - "/home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/msbuild/15.0/Bin"
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        MSBUILD_EXE_PATH environment variable set to '/home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/msbuild/15.0/Bin/MSBuild.dll'
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Registered MSBuild instance: StandAlone 15.0 - "/home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/msbuild/15.0/Bin"
            MSBuildExtensionsPath = /usr/lib/mono/xbuild
            CscToolPath = /home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/msbuild/15.0/Bin/Roslyn
            CscToolExe = csc.exe
            MSBuildToolsPath = /home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/msbuild/15.0/Bin
            TargetFrameworkRootPath = /usr/lib/mono/xbuild-frameworks
[dbug]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Attempting to resolve 'Microsoft.Build.Framework, Version=15.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'
[dbug]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Resolved 'Microsoft.Build.Framework' to '/home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/msbuild/15.0/Bin/Microsoft.Build.Framework.dll'
[dbug]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Attempting to resolve 'Microsoft.CodeAnalysis.VisualBasic.Workspaces, Version=2.4.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'
[dbug]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Attempting to resolve 'Microsoft.CodeAnalysis.VisualBasic.Features, Version=2.4.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'
[info]: OmniSharp.Cake.CakeProjectSystem
        Detecting Cake files in '/home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass'.
[info]: OmniSharp.Cake.CakeProjectSystem
        Could not find any Cake files
[info]: OmniSharp.DotNet.DotNetProjectSystem
        Initializing in /home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass
[info]: OmniSharp.DotNet.DotNetProjectSystem
        Auto package restore: False
[info]: OmniSharp.DotNet.DotNetProjectSystem
        Update workspace context
[info]: OmniSharp.DotNet.DotNetProjectSystem
        Resolving projects references
[dbug]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Attempting to resolve 'Microsoft.Build'
[dbug]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Resolved 'Microsoft.Build' to '/home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/msbuild/15.0/Bin/Microsoft.Build.dll'
[dbug]: OmniSharp.MSBuild.MSBuildProjectSystem
        MSBuild environment:
Mode: Standalone
RunningTests: False
RunningInVisualStudio: False
MSBuildToolsDirectory32: /home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/msbuild/15.0/Bin
MSBuildToolsDirectory64: /home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/msbuild/15.0/Bin
MSBuildSDKsPath: /home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/msbuild/15.0/Bin/Sdks
CurrentMSBuildConfigurationFile: /home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/msbuild/15.0/Bin/MSBuild.dll.config
CurrentMSBuildExePath: /home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/msbuild/15.0/Bin/MSBuild.dll
CurrentMSBuildToolsDirectory: /home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/msbuild/15.0/Bin
VisualStudioInstallRootDirectory:
MSBuildExtensionsPath: /home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/msbuild/15.0/Bin

[info]: OmniSharp.MSBuild.MSBuildProjectSystem
        No solution files found in '/home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass'
[info]: OmniSharp.MSBuild.MSBuildProjectSystem
        Loading project: /home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass/free-monad-vs-typeclass.csproj
[dbug]: OmniSharp.MSBuild.ProjectFile.ProjectFileInfo
        'MSBuildExtensionsPath' set to '/usr/lib/mono/xbuild'
[dbug]: OmniSharp.MSBuild.ProjectFile.ProjectFileInfo
        'TargetFrameworkRootPath' set to '/usr/lib/mono/xbuild-frameworks'
[dbug]: OmniSharp.MSBuild.ProjectFile.ProjectFileInfo
        'CscToolPath' set to '/home/jaccarmac/.vscode-insiders/extensions/ms-vscode.csharp-1.13.1/.omnisharp/omnisharp/msbuild/15.0/Bin/Roslyn'
[dbug]: OmniSharp.MSBuild.ProjectFile.ProjectFileInfo
        'CscToolExe' set to 'csc.exe'
[dbug]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Attempting to resolve 'Microsoft.Build.resources, Version=15.1.0.0, Culture=en-US, PublicKeyToken=b03f5f7f11d50a3a'
[dbug]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Attempting to resolve 'Microsoft.Build.resources, Version=15.1.0.0, Culture=en, PublicKeyToken=b03f5f7f11d50a3a'
[dbug]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Attempting to resolve 'Microsoft.Build.resources, Version=15.1.0.0, Culture=en-US, PublicKeyToken=b03f5f7f11d50a3a'
[dbug]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Attempting to resolve 'Microsoft.Build.resources, Version=15.1.0.0, Culture=en, PublicKeyToken=b03f5f7f11d50a3a'
[warn]: OmniSharp.MSBuild.MSBuildProjectSystem
        Failed to load project file '/home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass/free-monad-vs-typeclass.csproj'.
/home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass/free-monad-vs-typeclass.csproj(1,1)
Microsoft.Build.Exceptions.InvalidProjectFileException: The imported project "/usr/lib/mono/xbuild/15.0/Microsoft.Common.props" was not found. Confirm that the path in the <Import> declaration is correct, and that the file exists on disk.  /opt/dotnet_core/sdk/2.1.3/Sdks/Microsoft.NET.Sdk/Sdk/Sdk.props
  at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject (System.String errorSubCategoryResourceName, Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, System.Object[] args) [0x00042] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Shared.ProjectErrorUtilities.VerifyThrowInvalidProject[T1] (System.Boolean condition, System.String errorSubCategoryResourceName, Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, T1 arg0) [0x00003] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject[T1] (Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, T1 arg0) [0x00000] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].ExpandAndLoadImportsFromUnescapedImportExpression (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement, System.String unescapedExpression, System.Boolean throwOnFileNotExistsError, System.Collections.Generic.List`1[Microsoft.Build.Construction.ProjectRootElement]& imports) [0x00517] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].ExpandAndLoadImportsFromUnescapedImportExpressionConditioned (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement, System.Collections.Generic.List`1[Microsoft.Build.Construction.ProjectRootElement]& projects, System.Boolean throwOnFileNotExistsError) [0x001a6] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].ExpandAndLoadImports (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement) [0x00024] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].EvaluateImportElement (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement) [0x00000] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].PerformDepthFirstPass (Microsoft.Build.Construction.ProjectRootElement currentProjectOrImport) [0x001dd] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].EvaluateImportElement (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement) [0x0002d] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].PerformDepthFirstPass (Microsoft.Build.Construction.ProjectRootElement currentProjectOrImport) [0x000c8] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].Evaluate (Microsoft.Build.BackEnd.Logging.ILoggingService loggingService, Microsoft.Build.Framework.BuildEventContext buildEventContext) [0x000df] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].Evaluate (Microsoft.Build.Evaluation.IEvaluatorData`4[P,I,M,D] data, Microsoft.Build.Construction.ProjectRootElement root, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, System.Int32 maxNodeCount, Microsoft.Build.Collections.PropertyDictionary`1[T] environmentProperties, Microsoft.Build.BackEnd.Logging.ILoggingService loggingService, Microsoft.Build.Evaluation.IItemFactory`2[S,T] itemFactory, Microsoft.Build.Evaluation.IToolsetProvider toolsetProvider, Microsoft.Build.Evaluation.ProjectRootElementCache projectRootElementCache, Microsoft.Build.Framework.BuildEventContext buildEventContext, Microsoft.Build.Execution.ProjectInstance projectInstanceIfAnyForDebuggerOnly, Microsoft.Build.BackEnd.SdkResolution sdkResolution) [0x00016] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Project.Reevaluate (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x0004c] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x00034] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation) [0x00000] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary () [0x00007] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Project.Initialize (System.Collections.Generic.IDictionary`2[TKey,TValue] globalProperties, System.String toolsVersion, System.String subToolsetVersion, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x000e9] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary`2[TKey,TValue] globalProperties, System.String toolsVersion, System.String subToolsetVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x0009c] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary`2[TKey,TValue] globalProperties, System.String toolsVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x00000] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary`2[TKey,TValue] globalProperties, System.String toolsVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection) [0x00000] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.ProjectCollection.LoadProject (System.String fileName, System.Collections.Generic.IDictionary`2[TKey,TValue] globalProperties, System.String toolsVersion) [0x000f5] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at Microsoft.Build.Evaluation.ProjectCollection.LoadProject (System.String fileName, System.String toolsVersion) [0x00000] in <9ba305957e954df9b0ed46d97ba8f5be>:0
  at OmniSharp.MSBuild.ProjectFile.ProjectFileInfo.LoadProject (System.String filePath, System.String solutionDirectory, Microsoft.Extensions.Logging.ILogger logger, OmniSharp.MSBuild.Discovery.MSBuildInstance msbuildInstance, OmniSharp.MSBuild.SdksPathResolver sdksPathResolver, OmniSharp.Options.MSBuildOptions options, System.Collections.Generic.ICollection`1[T] diagnostics, System.Collections.Immutable.ImmutableArray`1[System.String]& targetFrameworks) [0x00054] in <e904597b17e840d49e5c532b51773be0>:0
  at OmniSharp.MSBuild.ProjectFile.ProjectFileInfo.Create (System.String filePath, System.String solutionDirectory, Microsoft.Extensions.Logging.ILogger logger, OmniSharp.MSBuild.Discovery.MSBuildInstance msbuildInstance, OmniSharp.MSBuild.SdksPathResolver sdksPathResolver, OmniSharp.Options.MSBuildOptions options, System.Collections.Generic.ICollection`1[T] diagnostics) [0x0000a] in <e904597b17e840d49e5c532b51773be0>:0
  at OmniSharp.MSBuild.MSBuildProjectSystem.LoadProject (System.String projectFilePath) [0x00038] in <e904597b17e840d49e5c532b51773be0>:0

[info]: OmniSharp.Script.ScriptProjectSystem
        Detecting CSX files in '/home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass'.
[info]: OmniSharp.Script.ScriptProjectSystem
        Could not find any CSX files
[info]: OmniSharp.Stdio.Host
        Invoking Workspace Options Provider: OmniSharp.Roslyn.CSharp.Services.CSharpWorkspaceOptionsProvider
[info]: OmniSharp.Stdio.Host
        Configuration finished.
[info]: OmniSharp.Stdio.Host
        Omnisharp server running using Stdio at location '/home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass' on host 18187.
[dbug]: OmniSharp.Stdio.Host
        ************ Request ************
{"Type":"request","Seq":1,"Command":"/projects"}
[dbug]: OmniSharp.Stdio.Host
        ************ Request ************
{"Type":"request","Seq":2,"Command":"/projects"}
[dbug]: OmniSharp.Stdio.Host
        ************  Response ************
{"Request_seq":2,"Command":"/projects","Running":true,"Success":true,"Message":null,"Body":{"Cake":{"Projects":[]},"DotNet":{"Projects":[],"RuntimePath":null},"MsBuild":{"SolutionPath":"/home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass","Projects":[]},"Script":{"Projects":[]}},"Seq":42,"Type":"response"}
[dbug]: OmniSharp.Stdio.Host
        ************  Response ************
{"Request_seq":1,"Command":"/projects","Running":true,"Success":true,"Message":null,"Body":{"Cake":{"Projects":[]},"DotNet":{"Projects":[],"RuntimePath":null},"MsBuild":{"SolutionPath":"/home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass","Projects":[]},"Script":{"Projects":[]}},"Seq":41,"Type":"response"}
[dbug]: OmniSharp.Stdio.Host
        ************ Request ************
{"Type":"request","Seq":3,"Command":"/projects"}
[dbug]: OmniSharp.Stdio.Host
        ************  Response ************
{"Request_seq":3,"Command":"/projects","Running":true,"Success":true,"Message":null,"Body":{"Cake":{"Projects":[]},"DotNet":{"Projects":[],"RuntimePath":null},"MsBuild":{"SolutionPath":"/home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass","Projects":[]},"Script":{"Projects":[]}},"Seq":46,"Type":"response"}
[dbug]: OmniSharp.Stdio.Host
        ************ Request ************
{"Type":"request","Seq":5,"Command":"/currentfilemembersastree","Arguments":{"FileName":"/home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass/Program.cs"}}
[dbug]: OmniSharp.Stdio.Host
        ************ Request ************
{"Type":"request","Seq":4,"Command":"/v2/getcodeactions","Arguments":{"FileName":"/home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass/Program.cs","Selection":{"Start":{"Line":1,"Column":1},"End":{"Line":1,"Column":1}}}}
[dbug]: OmniSharp.Stdio.Host
        ************  Response ************
{"Request_seq":5,"Command":"/currentfilemembersastree","Running":true,"Success":true,"Message":null,"Body":{"TopLevelTypeDefinitions":[]},"Seq":50,"Type":"response"}
[dbug]: OmniSharp.Stdio.Host
        ************ Request ************
{"Type":"request","Seq":6,"Command":"/v2/getcodeactions","Arguments":{"FileName":"/home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass/Program.cs","Line":16,"Column":56}}
[dbug]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Attempting to resolve 'Microsoft.CodeAnalysis.Workspaces.resources, Version=2.4.0.0, Culture=en-US, PublicKeyToken=31bf3856ad364e35'
[dbug]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Attempting to resolve 'Microsoft.CodeAnalysis.Workspaces.resources, Version=2.4.0.0, Culture=en, PublicKeyToken=31bf3856ad364e35'
[dbug]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Attempting to resolve 'Microsoft.CodeAnalysis.Features.resources, Version=2.4.0.0, Culture=en-US, PublicKeyToken=31bf3856ad364e35'
[dbug]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Attempting to resolve 'Microsoft.CodeAnalysis.Features.resources, Version=2.4.0.0, Culture=en, PublicKeyToken=31bf3856ad364e35'
[dbug]: OmniSharp.Stdio.Host
        ************  Response ************
{"Request_seq":6,"Command":"/v2/getcodeactions","Running":true,"Success":true,"Message":null,"Body":{"CodeActions":[]},"Seq":54,"Type":"response"}
[dbug]: OmniSharp.Stdio.Host
        ************  Response ************
{"Request_seq":4,"Command":"/v2/getcodeactions","Running":true,"Success":true,"Message":null,"Body":{"CodeActions":[]},"Seq":51,"Type":"response"}
[dbug]: OmniSharp.Stdio.Host
        ************ Request ************
{"Type":"request","Seq":7,"Command":"/codecheck","Arguments":{"FileName":"/home/jaccarmac/src/src/jaccarmac.com/junkcode/free-monad-vs-typeclass/Program.cs"}}
[dbug]: OmniSharp.Stdio.Host
        ************  Response ************
{"Request_seq":7,"Command":"/codecheck","Running":true,"Success":true,"Message":null,"Body":{"QuickFixes":[]},"Seq":62,"Type":"response"}
[dbug]: OmniSharp.Stdio.Host
        ************ Request ************
{"Type":"request","Seq":8,"Command":"/codecheck","Arguments":{"FileName":null}}
[dbug]: OmniSharp.Stdio.Host
        ************  Response ************
{"Request_seq":8,"Command":"/codecheck","Running":true,"Success":true,"Message":null,"Body":{"QuickFixes":[]},"Seq":65,"Type":"response"}

That error is very helpful for me. I don't have a DLL installed at that location. That DLL exists many other places on my system however. I don't want to dump the locate results here but perhaps the extension needs to check for other locations?

I will say that on Gentoo /usr/lib64 is used instead of /usr/lib for 64-bit libraries.

I don't have Gentoo installed anywhere, but are you saying the MSBuild is installed under /usr/lib64 somewhere?

Forgive me, I was imprecise.
No, MSBuild is not installed under /usr/lib64. It is located in /usr/share/msbuild.
However, while /usr/lib/mono exists it does not contain Microsoft.Build.dll as noted in the errors above. The actual Microsoft.Build.dll is in /usr/lib64/mono. (At least according to locate, if I go to the directory manually the files are in both places.)

I think I've worked out what the problem is.  Mono provide a package called msbuild, currently version 1:15.4+xamarinxplat.2017.11.27.11.23-0xamarin1+ubuntu1404b1.  It isn't a dependency of mono-devel, so it doesn't get installed if you install mono in the recommended way.  (It is a dependency of mono-complete.)
Installing this package prevents the error.  At this point I'm speculating, but perhaps if Mono is installed, Omnisharp tries to use it, and then fails because msbuild is missing.
I'm running Ubuntu (16.04) so your fix may be slightly different if you're on a different distro.

FWIW, there's a message in the OmniSharp Log above that reads:
It looks like you have Mono 5.2.0 or greater installed but MSBuild could not be found.
Try installing MSBuild into Mono (e.g. 'sudo apt-get install msbuild') to enable better MSBuild support.

@jaccarmac: Does sudo apt-get install msbuild address this problem for you?

Gentoo does not use APT for package management, so that particular command doesn't help here. However, I did install MSBuild. The error occurs before and after MSBuild is installed.

FYi: I uninstalled mono-develop (as I don’t need it anymore) and the problem was resolved. Not really a solution for this issue but maybe usefull to know.

@jaccarmac: I'm not familiar with Gentoo, so I'm not sure how installing packages works. How did you install MSBuild? The msbuild package for APT is produced by the Mono folks and installs into the Mono folder.

Gentoo uses what amount to recipes to build software from sources. So I used that. The executable and associated libraries are located in /usr/share/msbuild.

I can confirm the same issue.  If I have the package mono-devel installed, OmniSharp breaks and I get zero intellisense on .NET Core projects.  If I remove the package and restart Visual Studio Code, I get intellisense again.  This is a little frustrating as I am working on a Unity (engine) project (which requires Mono) as well as a .NET Core web application.  I'm running on Fedora 27 with the latest mono packages direct from the mono project's website: http://www.mono-project.com/download/stable/#download-lin-fedora

I'm having this same issue on Arch, but there isn't a mono-develop package that I can uninstall. If I uninstall the mono package, I still get this (link to gist of omnisharp log). I installed the .NET SDK via this package and VS Code from this package, if that helps.

I'm on arch solved this issue by uninstall "msbuild-bin" and install "msbuild-stable" (15.4_xamarinxplat.2017.11.27.11.23_0xamarin1_ubuntu1404b1-3) instead.

@sekseason The same worked for me, I am on manjaro.
I currently have mono installed via pacman and used yaourt to grab msbuild-stable from the aur.

Thanks for the advice on fixes all. The crux of the issue is that newer builds break OmniSharp in unpredictable ways. Downgrading fixes the symptom but not the actual problem.

On macOS uninstalling mono and re installing dotnet and dotnet-sdk packages fixes both emacs and vs code.

On fedora, after installing mono-complete (5.14.0.177) from the mono repo (mono-centos7-stable) I had this error. It was resolved after installing the msbuild package from the same repo (sudo dnf install msbuild)

I'm on Solus, and after I installed the mono-msbuild package from my system package manager, I'm experiencing similar problems but with different errors.  Installing that system package "permanently" broke Omnisharp.  Permanently, meaning something got set that isn't being unset when the package is removed.
I believe it may be related so I didn't want to start a new issue, but if I need to, let me know. I receive the error at the bottom of this comment.
Even after reverting my development system back to how it was initially, it's still trying to load system mono instead of the one supplied by omnisharp.  I did the following:

Uninstalled system mono-msbuild 15.8
Uninstalled system mono 5.14.0.177
Uninstalled all C# extensions
Uninstalled 3.0.100-preview3-010431
Uninstalled vscode
Reinstalled system mono, did not install mono-msbuild (at this point my system should be where it was initially)
Reinstalled dotnet core snap, vs code, c# extension

I still receive the same error every time VSCode starts up. I can no longer have mono installed on my system at all.
Before installing mono-msbuild from my package manager, I was getting the error mentioned in #2876, so even though it was broken at that point, it was at least looking in the right place for mono.  Now it isn't.
If I completely remove my system mono package, I get back to where I was with issue #2876, even though the problem started when I installed system mono-msbuild, which is no longer installed.
Hopefully my log will be of some help.  If anyone has any ideas how I can get mono reinstalled without interfering with omnisharp, I'm all ears.
Starting OmniSharp server at 3/20/2019, 8:49:59 AM
    Target: /home/adam/Source/internalproject

OmniSharp server started with Mono 5.14.0.
    Path: /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/OmniSharp.exe
    PID: 8362

[info]: OmniSharp.Stdio.Host
        Starting OmniSharp on solus 4.0 (x64)
[info]: OmniSharp.Services.DotNetCliService
        DotNetPath set to dotnet
Stacktrace:

  at <unknown> <0xffffffff>
  at (wrapper managed-to-native) OmniSharp.Utilities.PlatformHelper.Unix_free (intptr) [0x00002] in <182b3548f60947fcafa19b5fd56515a0>:0
  at OmniSharp.Utilities.PlatformHelper.RealPath (string) [0x0002d] in <182b3548f60947fcafa19b5fd56515a0>:0
  at OmniSharp.Utilities.PlatformHelper.GetMonoRuntimePath () [0x00050] in <182b3548f60947fcafa19b5fd56515a0>:0
  at OmniSharp.MSBuild.Discovery.Providers.MonoInstanceProvider.GetInstances () [0x0000d] in <ec3b9b744cc24b97b94be13e30b9e41f>:0
  at OmniSharp.MSBuild.Discovery.MSBuildLocator.GetInstances () [0x0001e] in <ec3b9b744cc24b97b94be13e30b9e41f>:0
  at OmniSharp.MSBuild.Discovery.Extensions.RegisterDefaultInstance (OmniSharp.MSBuild.Discovery.IMSBuildLocator,Microsoft.Extensions.Logging.ILogger) [0x00004] in <ec3b9b744cc24b97b94be13e30b9e41f>:0
  at OmniSharp.CompositionHostBuilder.Build () [0x0008b] in <ec3b9b744cc24b97b94be13e30b9e41f>:0
  at OmniSharp.Stdio.Host..ctor (System.IO.TextReader,OmniSharp.Stdio.Services.ISharedTextWriter,OmniSharp.IOmniSharpEnvironment,System.IServiceProvider,OmniSharp.CompositionHostBuilder,Microsoft.Extensions.Logging.ILoggerFactory,System.Threading.CancellationTokenSource) [0x00057] in <35cdcec6f502484d8825e1fc7493c665>:0
  at OmniSharp.Stdio.Driver.Program/<>c__DisplayClass0_1.<Main>b__1 () [0x00138] in <22c463206460470eafd215b3bb7ab1cd>:0
  at OmniSharp.CommandLineApplication/<>c__DisplayClass11_0.<OnExecute>b__0 () [0x0000b] in <ec3b9b744cc24b97b94be13e30b9e41f>:0
  at McMaster.Extensions.CommandLineUtils.CommandLineApplication.Execute (string[]) [0x00039] in <344a1e8cd6594b17b1e01f8df6ae8827>:0
  at OmniSharp.CommandLineApplication.Execute (System.Collections.Generic.IEnumerable`1<string>) [0x00042] in <ec3b9b744cc24b97b94be13e30b9e41f>:0
  at OmniSharp.Stdio.Driver.Program/<>c__DisplayClass0_0.<Main>b__0 () [0x00028] in <22c463206460470eafd215b3bb7ab1cd>:0
  at OmniSharp.HostHelpers.Start (System.Func`1<int>) [0x0001c] in <ec3b9b744cc24b97b94be13e30b9e41f>:0
  at OmniSharp.Stdio.Driver.Program.Main (string[]) [0x00005] in <22c463206460470eafd215b3bb7ab1cd>:0
  at (wrapper runtime-invoke) <Module>.runtime_invoke_int_object (object,intptr,intptr,intptr) [0x00054] in <22c463206460470eafd215b3bb7ab1cd>:0
/proc/self/maps:
00400000-00418000 r--p 00000000 103:03 23107333                          /usr/bin/mono-sgen
00418000-006f6000 r-xp 00018000 103:03 23107333                          /usr/bin/mono-sgen
006f6000-00817000 r--p 002f6000 103:03 23107333                          /usr/bin/mono-sgen
00817000-0081f000 r--p 00416000 103:03 23107333                          /usr/bin/mono-sgen
0081f000-00823000 rw-p 0041e000 103:03 23107333                          /usr/bin/mono-sgen
00823000-00839000 rw-p 00000000 00:00 0
02251000-02b0d000 rw-p 00000000 00:00 0                                  [heap]
4138c000-4139c000 rwxp 00000000 00:00 0
41fd7000-420f1000 rwxp 00000000 00:00 0
7fedf8000000-7fedf8021000 rw-p 00000000 00:00 0
7fedf8021000-7fedfc000000 ---p 00000000 00:00 0
7fedffafb000-7fedffdfd000 r--p 00000000 103:03 26223857                  /usr/lib64/mono/gac/System.Xml/4.0.0.0__b77a5c561934e089/System.Xml.dll
7fedffdfd000-7fee00000000 r--p 00000000 103:03 25565809                  /usr/lib64/mono/gac/System.Data/4.0.0.0__b77a5c561934e089/System.Data.dll
7fee00000000-7fee00021000 rw-p 00000000 00:00 0
7fee00021000-7fee04000000 ---p 00000000 00:00 0
7fee04000000-7fee0404d000 rw-p 00000000 00:00 0
7fee0404d000-7fee08000000 ---p 00000000 00:00 0
7fee08000000-7fee08050000 rw-p 00000000 00:00 0
7fee08050000-7fee0c000000 ---p 00000000 00:00 0
7fee0c000000-7fee0c021000 rw-p 00000000 00:00 0
7fee0c021000-7fee10000000 ---p 00000000 00:00 0
7fee10000000-7fee10021000 rw-p 00000000 00:00 0
7fee10021000-7fee14000000 ---p 00000000 00:00 0
7fee14000000-7fee1437e000 rw-p 00000000 00:00 0
7fee1437e000-7fee18000000 ---p 00000000 00:00 0
7fee18000000-7fee18021000 rw-p 00000000 00:00 0
7fee18021000-7fee1c000000 ---p 00000000 00:00 0
7fee1c16f000-7fee1c1b9000 r--p 00000000 103:03 21236250                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/System.Collections.Immutable.dll
7fee1c1b9000-7fee1c1ba000 rw-p 00000000 00:00 0
7fee1c1ba000-7fee1c1ca000 rwxp 00000000 00:00 0
7fee1c1ca000-7fee1c1d8000 r--p 00000000 103:03 21236087                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/NuGet.Versioning.dll
7fee1c1d8000-7fee1c2bc000 r--p 00000000 103:03 25828019                  /usr/lib64/mono/gac/System.Runtime.Serialization/4.0.0.0__b77a5c561934e089/System.Runtime.Serialization.dll
7fee1c2bc000-7fee1c555000 r--p 00000000 103:03 21235532                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.CodeAnalysis.dll
7fee1c555000-7fee1c55b000 r--p 00000000 103:03 21236253                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/System.Collections.dll
7fee1c55b000-7fee1c561000 r--p 00000000 103:03 21236336                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/System.Threading.dll
7fee1c561000-7fee1c568000 r--p 00000000 103:03 21236256                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/System.Composition.AttributedModel.dll
7fee1c568000-7fee1c578000 r--p 00000000 103:03 21236260                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/System.Composition.TypedParts.dll
7fee1c578000-7fee1c5a2000 r--p 00000000 103:03 21236232                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/OmniSharp.Roslyn.CSharp.dll
7fee1c5a2000-7fee1c5b4000 r--p 00000000 103:03 21236228                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/OmniSharp.MSBuild.dll
7fee1c5b4000-7fee1c5c1000 r--p 00000000 103:03 21236096                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/OmniSharp.DotNetTest.dll
7fee1c5c1000-7fee1c5ca000 r--p 00000000 103:03 21236094                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/OmniSharp.DotNet.dll
7fee1c5ca000-7fee1c5ec000 r--p 00000000 103:03 23228411                  /usr/lib64/libc-2.29.so
7fee1c5ec000-7fee1c75e000 r-xp 00022000 103:03 23228411                  /usr/lib64/libc-2.29.so
7fee1c75e000-7fee1c7aa000 r--p 00194000 103:03 23228411                  /usr/lib64/libc-2.29.so
7fee1c7aa000-7fee1c7ab000 ---p 001e0000 103:03 23228411                  /usr/lib64/libc-2.29.so
7fee1c7ab000-7fee1c7af000 r--p 001e0000 103:03 23228411                  /usr/lib64/libc-2.29.so
7fee1c7af000-7fee1c7b1000 rw-p 001e4000 103:03 23228411                  /usr/lib64/libc-2.29.so
7fee1c7b1000-7fee1c7b5000 rw-p 00000000 00:00 0
7fee1c7b5000-7fee1c857000 r--p 00000000 103:03 21236077                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Newtonsoft.Json.dll
7fee1c857000-7fee1caff000 r--p 00000000 103:03 21235531                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.CodeAnalysis.Workspaces.dll
7fee1caff000-7fee1cb00000 ---p 00000000 00:00 0
7fee1cb00000-7fee1cb01000 rw-p 00000000 00:00 0
7fee1cb01000-7fee1cb09000 ---p 00000000 00:00 0
7fee1cb09000-7fee1ce00000 rw-p 00000000 00:00 0
7fee1ce00000-7fee1ce07000 r--p 00000000 103:03 21236236                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/OmniSharp.Script.dll
7fee1ce07000-7fee1ce1a000 r--p 00000000 103:03 21236090                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/OmniSharp.Cake.dll
7fee1ce1a000-7fee1ce20000 r--p 00000000 103:03 21235533                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.DotNet.PlatformAbstractions.dll
7fee1ce20000-7fee1ce3f000 r--p 00000000 103:03 25691462                  /usr/lib64/mono/gac/System.Numerics/4.0.0.0__b77a5c561934e089/System.Numerics.dll
7fee1ce3f000-7fee1ce4f000 r--p 00000000 103:03 21235558                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.Extensions.DependencyModel.dll
7fee1ce4f000-7fee1ce5f000 r--p 00000000 103:03 21236234                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/OmniSharp.Roslyn.dll
7fee1ce5f000-7fee1ce66000 r--p 00000000 103:03 21235537                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.Extensions.Configuration.Binder.dll
7fee1ce66000-7fee1ce6b000 r--p 00000000 103:03 21236064                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.Extensions.Options.ConfigurationExtensions.dll
7fee1ce6b000-7fee1ce75000 r--p 00000000 103:03 21236065                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.Extensions.Options.dll
7fee1ce75000-7fee1ce7d000 r--p 00000000 103:03 21235535                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.Extensions.Caching.Memory.dll
7fee1ce7d000-7fee1ce84000 r--p 00000000 103:03 21235534                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.Extensions.Caching.Abstractions.dll
7fee1ce84000-7fee1ce8c000 rw-p 00000000 00:00 0
7fee1ce8c000-7fee1ce8d000 ---p 00000000 00:00 0
7fee1ce8d000-7fee1ce8e000 rw-p 00000000 00:00 0
7fee1ce8e000-7fee1ce96000 ---p 00000000 00:00 0
7fee1ce96000-7fee1d091000 rw-p 00000000 00:00 0
7fee1d091000-7fee1d092000 ---p 00000000 00:00 0
7fee1d092000-7fee1d093000 rw-p 00000000 00:00 0
7fee1d093000-7fee1d09b000 ---p 00000000 00:00 0
7fee1d09b000-7fee1d296000 rw-p 00000000 00:00 0
7fee1d296000-7fee1d297000 ---p 00000000 00:00 0
7fee1d297000-7fee1d298000 rw-p 00000000 00:00 0
7fee1d298000-7fee1d2a0000 ---p 00000000 00:00 0
7fee1d2a0000-7fee1d49b000 rw-p 00000000 00:00 0
7fee1d49b000-7fee1d49c000 ---p 00000000 00:00 0
7fee1d49c000-7fee1d49d000 rw-p 00000000 00:00 0
7fee1d49d000-7fee1d4a5000 ---p 00000000 00:00 0
7fee1d4a5000-7fee1d6a0000 rw-p 00000000 00:00 0
7fee1d6a0000-7fee1d6a1000 ---p 00000000 00:00 0
7fee1d6a1000-7fee1d6a2000 rw-p 00000000 00:00 0
7fee1d6a2000-7fee1d6aa000 ---p 00000000 00:00 0
7fee1d6aa000-7fee1d8a1000 rw-p 00000000 00:00 0
7fee1d8a1000-7fee1d8a7000 r--p 00000000 103:03 21235541                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.Extensions.Configuration.Json.dll
7fee1d8a7000-7fee1d8ac000 r--p 00000000 103:03 21235538                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.Extensions.Configuration.CommandLine.dll
7fee1d8ac000-7fee1d8b1000 r--p 00000000 103:03 21235539                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.Extensions.Configuration.EnvironmentVariables.dll
7fee1d8b1000-7fee1d8bb000 r--p 00000000 103:03 21235747                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.Extensions.FileSystemGlobbing.dll
7fee1d8bb000-7fee1d8c4000 r--p 00000000 103:03 21236069                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.Extensions.Primitives.dll
7fee1d8c4000-7fee1d8c9000 r--p 00000000 103:03 21235743                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.Extensions.FileProviders.Abstractions.dll
7fee1d8c9000-7fee1d8d1000 r--p 00000000 103:03 21235745                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.Extensions.FileProviders.Physical.dll
7fee1d8d1000-7fee1d8d7000 r--p 00000000 103:03 21235540                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.Extensions.Configuration.FileExtensions.dll
7fee1d8d7000-7fee1d8de000 r--p 00000000 103:03 21235542                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.Extensions.Configuration.dll
7fee1d8de000-7fee1d92a000 r--p 00000000 103:03 24128144                  /usr/lib64/mono/gac/Mono.Security/4.0.0.0__0738eb9f132ed756/Mono.Security.dll
7fee1d92a000-7fee1d948000 r--p 00000000 103:03 25043018                  /usr/lib64/mono/gac/System.Configuration/4.0.0.0__b03f5f7f11d50a3a/System.Configuration.dll
7fee1d948000-7fee1d950000 r--p 00000000 103:03 21236063                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.Extensions.Logging.dll
7fee1d950000-7fee1d958000 r--p 00000000 103:03 21236319                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/System.Runtime.dll
7fee1d958000-7fee1d960000 r--p 00000000 103:03 21236259                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/System.Composition.Runtime.dll
7fee1d960000-7fee1d970000 r--p 00000000 103:03 21236258                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/System.Composition.Hosting.dll
7fee1d970000-7fee1d979000 r--p 00000000 103:03 21236098                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/OmniSharp.Extensions.JsonRpc.dll
7fee1d979000-7fee1d998000 r--p 00000000 103:03 21236099                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/OmniSharp.Extensions.LanguageServerProtocol.dll
7fee1d998000-7fee1d9a1000 r--p 00000000 103:03 21235543                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.Extensions.DependencyInjection.Abstractions.dll
7fee1d9a1000-7fee1d9b0000 r--p 00000000 103:03 21235548                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.Extensions.DependencyInjection.dll
7fee1d9b0000-7fee1d9c9000 r--p 00000000 103:03 21236345                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/netstandard.dll
7fee1d9c9000-7fee1d9d5000 r--p 00000000 103:03 21235932                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.Extensions.Logging.Abstractions.dll
7fee1d9d5000-7fee1d9da000 r--p 00000000 103:03 21235536                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/Microsoft.Extensions.Configuration.Abstractions.dll
7fee1d9da000-7fee1dad3000 r--p 00000000 103:03 25043022                  /usr/lib64/mono/gac/System.Core/4.0.0.0__b77a5c561934e089/System.Core.dll
7fee1dad3000-7fee1dd96000 r--p 00000000 103:03 26223861                  /usr/lib64/mono/gac/System/4.0.0.0__b77a5c561934e089/System.dll
7fee1dd96000-7fee1ddab000 r--p 00000000 103:03 24904601                  /usr/lib64/mono/gac/System.ComponentModel.DataAnnotations/4.0.0.0__31bf3856ad364e35/System.ComponentModel.DataAnnotations.dll
7fee1ddab000-7fee1ddac000 ---p 00000000 00:00 0
7fee1ddac000-7fee1ddad000 rw-p 00000000 00:00 0
7fee1ddad000-7fee1ddb5000 ---p 00000000 00:00 0
7fee1ddb5000-7fee1e02d000 rw-p 00000000 00:00 0
7fee1e02d000-7fee1e3ff000 r--p 00000000 103:03 23359197                  /usr/lib64/mono/4.5/mscorlib.dll
7fee1e3ff000-7fee1f3ff000 rw-p 00000000 00:00 0
7fee1f3ff000-7fee1f400000 ---p 00000000 00:00 0
7fee1f400000-7fee20000000 rw-p 00000000 00:00 0
7fee20000000-7fee20003000 r--p 00000000 103:03 21236230                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/OmniSharp.Plugins.dll
7fee20003000-7fee20012000 r--p 00000000 103:03 21236102                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/OmniSharp.LanguageServerProtocol.dll
7fee20012000-7fee20034000 r--p 00000000 103:03 21235523                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/McMaster.Extensions.CommandLineUtils.dll
7fee20034000-7fee20039000 r--p 00000000 103:03 21236238                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/OmniSharp.Stdio.dll
7fee20039000-7fee20055000 r--p 00000000 103:03 21236088                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/OmniSharp.Abstractions.dll
7fee20055000-7fee20056000 rw-p 00000000 00:00 0
7fee20056000-7fee200b5000 ---p 00000000 00:00 0
7fee200b5000-7fee2d056000 r--p 00000000 103:03 24258542                  /usr/lib64/locale/locale-archive
7fee2d056000-7fee2d05b000 rw-p 00000000 00:00 0
7fee2d05b000-7fee2d07d000 r--p 00000000 103:03 24258534                  /usr/lib64/haswell/libc-2.29.so
7fee2d07d000-7fee2d1ed000 r-xp 00022000 103:03 24258534                  /usr/lib64/haswell/libc-2.29.so
7fee2d1ed000-7fee2d239000 r--p 00192000 103:03 24258534                  /usr/lib64/haswell/libc-2.29.so
7fee2d239000-7fee2d23a000 ---p 001de000 103:03 24258534                  /usr/lib64/haswell/libc-2.29.so
7fee2d23a000-7fee2d23e000 r--p 001de000 103:03 24258534                  /usr/lib64/haswell/libc-2.29.so
7fee2d23e000-7fee2d240000 rw-p 001e2000 103:03 24258534                  /usr/lib64/haswell/libc-2.29.so
7fee2d240000-7fee2d244000 rw-p 00000000 00:00 0
7fee2d244000-7fee2d247000 r--p 00000000 103:03 23223771                  /usr/lib64/libgcc_s.so.1
7fee2d247000-7fee2d259000 r-xp 00003000 103:03 23223771                  /usr/lib64/libgcc_s.so.1
7fee2d259000-7fee2d25c000 r--p 00015000 103:03 23223771                  /usr/lib64/libgcc_s.so.1
7fee2d25c000-7fee2d25d000 ---p 00018000 103:03 23223771                  /usr/lib64/libgcc_s.so.1
7fee2d25d000-7fee2d25e000 r--p 00018000 103:03 23223771                  /usr/lib64/libgcc_s.so.1
7fee2d25e000-7fee2d25f000 rw-p 00019000 103:03 23223771                  /usr/lib64/libgcc_s.so.1
7fee2d25f000-7fee2d265000 r--p 00000000 103:03 23228424                  /usr/lib64/libpthread-2.29.so
7fee2d265000-7fee2d274000 r-xp 00006000 103:03 23228424                  /usr/lib64/libpthread-2.29.so
7fee2d274000-7fee2d27a000 r--p 00015000 103:03 23228424                  /usr/lib64/libpthread-2.29.so
7fee2d27a000-7fee2d27b000 r--p 0001a000 103:03 23228424                  /usr/lib64/libpthread-2.29.so
7fee2d27b000-7fee2d27c000 rw-p 0001b000 103:03 23228424                  /usr/lib64/libpthread-2.29.so
7fee2d27c000-7fee2d280000 rw-p 00000000 00:00 0
7fee2d280000-7fee2d281000 r--p 00000000 103:03 23228413                  /usr/lib64/libdl-2.29.so
7fee2d281000-7fee2d283000 r-xp 00001000 103:03 23228413                  /usr/lib64/libdl-2.29.so
7fee2d283000-7fee2d284000 r--p 00003000 103:03 23228413                  /usr/lib64/libdl-2.29.so
7fee2d284000-7fee2d285000 r--p 00003000 103:03 23228413                  /usr/lib64/libdl-2.29.so
7fee2d285000-7fee2d286000 rw-p 00004000 103:03 23228413                  /usr/lib64/libdl-2.29.so
7fee2d286000-7fee2d288000 r--p 00000000 103:03 23228426                  /usr/lib64/librt-2.29.so
7fee2d288000-7fee2d28c000 r-xp 00002000 103:03 23228426                  /usr/lib64/librt-2.29.so
7fee2d28c000-7fee2d28e000 r--p 00006000 103:03 23228426                  /usr/lib64/librt-2.29.so
7fee2d28e000-7fee2d28f000 r--p 00007000 103:03 23228426                  /usr/lib64/librt-2.29.so
7fee2d28f000-7fee2d290000 rw-p 00008000 103:03 23228426                  /usr/lib64/librt-2.29.so
7fee2d290000-7fee2d29d000 r--p 00000000 103:03 24258538                  /usr/lib64/haswell/libm-2.29.so
7fee2d29d000-7fee2d335000 r-xp 0000d000 103:03 24258538                  /usr/lib64/haswell/libm-2.29.so
7fee2d335000-7fee2d3cd000 r--p 000a5000 103:03 24258538                  /usr/lib64/haswell/libm-2.29.so
7fee2d3cd000-7fee2d3ce000 r--p 0013c000 103:03 24258538                  /usr/lib64/haswell/libm-2.29.so
7fee2d3ce000-7fee2d3cf000 rw-p 0013d000 103:03 24258538                  /usr/lib64/haswell/libm-2.29.so
7fee2d3cf000-7fee2d3d2000 rw-p 00000000 00:00 0
7fee2d3d2000-7fee2d3d3000 rw-p 00000000 00:00 0
7fee2d3d3000-7fee2d3e2000 r--p 00000000 103:03 21236100                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/OmniSharp.Host.dll
7fee2d3e2000-7fee2d3e4000 r--p 00000000 103:03 21236241                  /home/adam/.vscode/extensions/ms-vscode.csharp-1.17.1/.omnisharp/1.32.8/omnisharp/OmniSharp.exe
7fee2d3e4000-7fee2d3f9000 rw-p 00000000 00:00 0
7fee2d3f9000-7fee2d3fa000 rw-s 00000000 00:13 189186                     /dev/shm/mono.8362
7fee2d3fa000-7fee2d3fb000 r--p 00000000 103:03 23225062                  /usr/lib64/ld-2.29.so
7fee2d3fb000-7fee2d41b000 r-xp 00001000 103:03 23225062                  /usr/lib64/ld-2.29.so
7fee2d41b000-7fee2d423000 r--p 00021000 103:03 23225062                  /usr/lib64/ld-2.29.so
7fee2d423000-7fee2d424000 r--p 00028000 103:03 23225062                  /usr/lib64/ld-2.29.so
7fee2d424000-7fee2d425000 rw-p 00029000 103:03 23225062                  /usr/lib64/ld-2.29.so
7fee2d425000-7fee2d426000 rw-p 00000000 00:00 0
7ffec8a48000-7ffec8a50000 ---p 00000000 00:00 0
7ffec9226000-7ffec9247000 rw-p 00000000 00:00 0                          [stack]
7ffec93e1000-7ffec93e4000 r--p 00000000 00:00 0                          [vvar]
7ffec93e4000-7ffec93e6000 r-xp 00000000 00:00 0                          [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]

Native stacktrace:

System.NullReferenceException: Object reference not set to an instance of an object
  at (wrapper managed-to-native) OmniSharp.Utilities.PlatformHelper.Unix_free(intptr)
  at OmniSharp.Utilities.PlatformHelper.RealPath (System.String path) [0x0002d] in <182b3548f60947fcafa19b5fd56515a0>:0
  at OmniSharp.Utilities.PlatformHelper.GetMonoRuntimePath () [0x00050] in <182b3548f60947fcafa19b5fd56515a0>:0
  at OmniSharp.MSBuild.Discovery.Providers.MonoInstanceProvider.GetInstances () [0x0000d] in <ec3b9b744cc24b97b94be13e30b9e41f>:0
  at OmniSharp.MSBuild.Discovery.MSBuildLocator.GetInstances () [0x0001e] in <ec3b9b744cc24b97b94be13e30b9e41f>:0
  at OmniSharp.MSBuild.Discovery.Extensions.RegisterDefaultInstance (OmniSharp.MSBuild.Discovery.IMSBuildLocator msbuildLocator, Microsoft.Extensions.Logging.ILogger logger) [0x00004] in <ec3b9b744cc24b97b94be13e30b9e41f>:0
  at OmniSharp.CompositionHostBuilder.Build () [0x0008b] in <ec3b9b744cc24b97b94be13e30b9e41f>:0
  at OmniSharp.Stdio.Host..ctor (System.IO.TextReader input, OmniSharp.Stdio.Services.ISharedTextWriter writer, OmniSharp.IOmniSharpEnvironment environment, System.IServiceProvider serviceProvider, OmniSharp.CompositionHostBuilder compositionHostBuilder, Microsoft.Extensions.Logging.ILoggerFactory loggerFactory, System.Threading.CancellationTokenSource cancellationTokenSource) [0x00057] in <35cdcec6f502484d8825e1fc7493c665>:0
  at OmniSharp.Stdio.Driver.Program+<>c__DisplayClass0_1.<Main>b__1 () [0x00138] in <22c463206460470eafd215b3bb7ab1cd>:0
  at OmniSharp.CommandLineApplication+<>c__DisplayClass11_0.<OnExecute>b__0 () [0x0000b] in <ec3b9b744cc24b97b94be13e30b9e41f>:0
  at McMaster.Extensions.CommandLineUtils.CommandLineApplication.Execute (System.String[] args) [0x00039] in <344a1e8cd6594b17b1e01f8df6ae8827>:0
  at OmniSharp.CommandLineApplication.Execute (System.Collections.Generic.IEnumerable`1[T] args) [0x00042] in <ec3b9b744cc24b97b94be13e30b9e41f>:0
  at OmniSharp.Stdio.Driver.Program+<>c__DisplayClass0_0.<Main>b__0 () [0x00028] in <22c463206460470eafd215b3bb7ab1cd>:0
  at OmniSharp.HostHelpers.Start (System.Func`1[TResult] action) [0x0001c] in <ec3b9b744cc24b97b94be13e30b9e41f>:0

@arcooke Have you found a way to work around this? Seeing how you opened another issue recently. Would be great if Solus users can have a solution for this as otherwise we're pretty much stuck.
If not, I guess all we can do is wait for the mono 5.18 update that's going to land in the solus repos sooner or later

Could you try setting "omnisharp.useGlobalMono": never and then restarting the omnisharp server.

@akshita31 and @curtisy1
That tip seemed to do the trick, thank you. The  mono and mono-msbuild packages installed on my system are now ignored when Omnisharp starts up
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Located 1 MSBuild instance(s)
            1: StandAlone 15.0 - "/home/adam/.vscode/extensions/ms-vscode.csharp-1.19.1/.omnisharp/1.32.20-beta.29/omnisharp/.msbuild/Current/Bin"
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        MSBUILD_EXE_PATH environment variable set to '/home/adam/.vscode/extensions/ms-vscode.csharp-1.19.1/.omnisharp/1.32.20-beta.29/omnisharp/.msbuild/Current/Bin/MSBuild.dll'
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Registered MSBuild instance: StandAlone 15.0 - "/home/adam/.vscode/extensions/ms-vscode.csharp-1.19.1/.omnisharp/1.32.20-beta.29/omnisharp/.msbuild/Current/Bin"
            MSBuildExtensionsPath = /usr/lib/mono/xbuild
            BypassFrameworkInstallChecks = true
            CscToolPath = /home/adam/.vscode/extensions/ms-vscode.csharp-1.19.1/.omnisharp/1.32.20-beta.29/omnisharp/.msbuild/Current/Bin/Roslyn
            CscToolExe = csc.exe
            MSBuildToolsPath = /home/adam/.vscode/extensions/ms-vscode.csharp-1.19.1/.omnisharp/1.32.20-beta.29/omnisharp/.msbuild/Current/Bin
            TargetFrameworkRootPath = /usr/lib/mono/xbuild-frameworks

@akshita31 Yes, can confirm it works perfectly. Thanks for the help!

@curtisy1 @arcooke Glad you got it working. It looks the default mono on your system has something missing which was causing the problem. Setting the above option would force omnisharp to use the mono version that ships with it.
I will close this issue now. Please reopen if it appears again

What are the debugging steps for this issue if it persists after setting omnisharp.useGlobalMono to never?
I'm getting seemingly the same issue and don't want to create a new issue if its the same problem...
OmniSharp log
Mono:
Mono JIT compiler version 5.18.1.3 (tarball Tue May 14 10:24:27 UTC 2019)
Copyright (C) 2002-2014 Novell, Inc, Xamarin Inc and Contributors. www.mono-project.com

dotnet:
.NET Core SDK (reflecting any global.json):
 Version:   2.2.300
 Commit:    73efd5bd87

Runtime Environment:
 OS Name:     fedora
 OS Version:  30
 OS Platform: Linux
 RID:         linux-x64
 Base Path:   /usr/share/dotnet/sdk/2.2.300/

Host (useful for support):
  Version: 2.2.5
  Commit:  0a3c9209c0

.NET Core SDKs installed:
  2.1.700 [/usr/share/dotnet/sdk]
  2.2.300 [/usr/share/dotnet/sdk]

I can create a new issue if preferred, its just this looks like the exact same symptoms.

I also get the error on OpenSuSe Leap 15.1, even when setting useGlobalMono to never

@agc93 Could you try the fix as mentioned in the comments above, like this one https://github.com/OmniSharp/omnisharp-vscode/issues/1998#issuecomment-380303803

@akshita31 I don't have either msbuild-bin or msbuild-stable packages available.
[root@fbb3dc645236 /]# dnf search msbuild
Last metadata expiration check: 0:01:24 ago on Fri 28 Jun 2019 01:39:55 AM UTC.
No matches found.

Just wanted to share the workaround I've been using for months now.
I'm on Arch. I have msbuild-stable 16.0_xamarinxplat.2018.09.26.17.53_0xamarin3_ubuntu1404b1-1 and mono 6.0.0.319-1.
Setting useGlobalMono to never had no effect.
My workaround:
sudo ln -s ~/.vscode/extensions/ms-vscode.csharp-1.21.1/.omnisharp/1.34.3-beta.22/omnisharp/.msbuild/15.0/Microsoft.Common.props /usr/lib/mono/xbuild/15.0/Microsoft.Common.props
Obvious downside is having to update the symlink when I update omnisharp, but I've been using this for months with no problem.

@akshita31 Is there any update on this issue, or do I need to open a new one? Even with the latest 3.0 SDK installed, Omnisharp still doesn't work, failing with the same error around Microsoft.Common.props

@akshita31 Is there any update on this issue, or do I need to open a new one? Even with the latest 3.0 SDK installed, Omnisharp still doesn't work, failing with the same error around Microsoft.Common.props

Same here... Omnisharp seems to break for me every couple of months.

please provide the OmniSharp log - we will have a look.
also please note that there is a known issue on Arch #3316

This is on Ubuntu 19.04
Microsoft.Build.Exceptions.InvalidProjectFileException: The imported project "/usr/lib/mono/xbuild/15.0/Microsoft.Common.props" was not found. Confirm that the path in the <Import> declaration is correct, and that the file exists on disk.  /usr/share/dotnet/sdk/3.0.100/Sdks/Microsoft.NET.Sdk/Sdk/Sdk.props   at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject (System.String errorSubCategoryResourceName, Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, System.Object[] args) [0x00040] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Shared.ProjectErrorUtilities.VerifyThrowInvalidProject[T1] (System.Boolean condition, System.String errorSubCategoryResourceName, Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, T1 arg0) [0x00003] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject[T1] (Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, T1 arg0) [0x00000] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].ExpandAndLoadImportsFromUnescapedImportExpression (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement, System.String unescapedExpression, System.Boolean throwOnFileNotExistsError, System.Collections.Generic.List1[Microsoft.Build.Construction.ProjectRootElement]& imports) [0x0060f] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].ExpandAndLoadImportsFromUnescapedImportExpressionConditioned (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement, System.Collections.Generic.List1[Microsoft.Build.Construction.ProjectRootElement]& projects, Microsoft.Build.BackEnd.SdkResolution.SdkResult& sdkResult, System.Boolean throwOnFileNotExistsError) [0x00268] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].ExpandAndLoadImports (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement, Microsoft.Build.BackEnd.SdkResolution.SdkResult& sdkResult) [0x00027] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].EvaluateImportElement (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement) [0x0000d] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].PerformDepthFirstPass (Microsoft.Build.Construction.ProjectRootElement currentProjectOrImport) [0x00209] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].EvaluateImportElement (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement) [0x00040] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].PerformDepthFirstPass (Microsoft.Build.Construction.ProjectRootElement currentProjectOrImport) [0x00209] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].EvaluateImportElement (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement) [0x00040] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].PerformDepthFirstPass (Microsoft.Build.Construction.ProjectRootElement currentProjectOrImport) [0x000e6] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].Evaluate (Microsoft.Build.BackEnd.Logging.ILoggingService loggingService, Microsoft.Build.Framework.BuildEventContext buildEventContext) [0x0011c] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].Evaluate (Microsoft.Build.Evaluation.IEvaluatorData4[P,I,M,D] data, Microsoft.Build.Construction.ProjectRootElement root, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, System.Int32 maxNodeCount, Microsoft.Build.Collections.PropertyDictionary1[T] environmentProperties, Microsoft.Build.BackEnd.Logging.ILoggingService loggingService, Microsoft.Build.Evaluation.IItemFactory2[S,T] itemFactory, Microsoft.Build.Evaluation.IToolsetProvider toolsetProvider, Microsoft.Build.Evaluation.ProjectRootElementCache projectRootElementCache, Microsoft.Build.Framework.BuildEventContext buildEventContext, Microsoft.Build.BackEnd.SdkResolution.ISdkResolverService sdkResolverService, System.Int32 submissionId, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext, System.Boolean interactive) [0x0002f] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Project.Reevaluate (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x0005e] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00035] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00000] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00007] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Project.Initialize (System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, System.String subToolsetVersion, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00126] in :0
at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, System.String subToolsetVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00093] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, System.String subToolsetVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x00000] in :0
at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x00000] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection) [0x00000] in :0
at Microsoft.Build.Evaluation.ProjectCollection.LoadProject (System.String fileName, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion) [0x000f7] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.ProjectCollection.LoadProject (System.String fileName, System.String toolsVersion) [0x00000] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at OmniSharp.MSBuild.ProjectLoader.EvaluateProjectFileCore (System.String filePath) [0x0003f] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0    at OmniSharp.MSBuild.ProjectLoader.BuildProject (System.String filePath) [0x0000d] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0    at OmniSharp.MSBuild.ProjectFile.ProjectFileInfo.Load (System.String filePath, OmniSharp.MSBuild.ProjectIdInfo projectIdInfo, OmniSharp.MSBuild.ProjectLoader loader) [0x00015] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0    at OmniSharp.MSBuild.ProjectManager+<>c__DisplayClass29_0.<LoadProject>b__0 () [0x00000] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0    at (wrapper delegate-invoke) System.Func1[System.ValueTuple3[OmniSharp.MSBuild.ProjectFile.ProjectFileInfo,System.Collections.Immutable.ImmutableArray1[OmniSharp.MSBuild.Logging.MSBuildDiagnostic],OmniSharp.MSBuild.Notification.ProjectLoadedEventArgs]].invoke_TResult()
at OmniSharp.MSBuild.ProjectManager.LoadOrReloadProject (System.String projectFilePath, System.Func1[TResult] loader) [0x0001b] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0

can you please post the full log though?

Apologies... here you go..
Starting OmniSharp server at 4/10/2019, 21:20:58
Target: /home/fergalm/dev/myproj/myproj-backend/myproj-backend.sln
OmniSharp server started.
Path: /home/fergalm/.vscode-insiders/extensions/ms-vscode.csharp-1.21.4/.omnisharp/1.34.4/run
PID: 10006
    Starting OmniSharp on ubuntu 19.4 (x64)

    DotNetPath set to dotnet

    Located 1 MSBuild instance(s)
        1: StandAlone 16.0 - "/home/fergalm/.vscode-insiders/extensions/ms-vscode.csharp-1.21.4/.omnisharp/1.34.4/omnisharp/.msbuild/Current/Bin"

    MSBUILD_EXE_PATH environment variable set to '/home/fergalm/.vscode-insiders/extensions/ms-vscode.csharp-1.21.4/.omnisharp/1.34.4/omnisharp/.msbuild/Current/Bin/MSBuild.dll'

    Registered MSBuild instance: StandAlone 16.0 - "/home/fergalm/.vscode-insiders/extensions/ms-vscode.csharp-1.21.4/.omnisharp/1.34.4/omnisharp/.msbuild/Current/Bin"
        MSBuildExtensionsPath = /usr/lib/mono/xbuild
        BypassFrameworkInstallChecks = true
        CscToolPath = /home/fergalm/.vscode-insiders/extensions/ms-vscode.csharp-1.21.4/.omnisharp/1.34.4/omnisharp/.msbuild/Current/Bin/Roslyn
        CscToolExe = csc.exe
        MSBuildToolsPath = /home/fergalm/.vscode-insiders/extensions/ms-vscode.csharp-1.21.4/.omnisharp/1.34.4/omnisharp/.msbuild/Current/Bin
        TargetFrameworkRootPath = /usr/lib/mono/xbuild-frameworks

    Detecting Cake files in '/home/fergalm/dev/myproj/myproj-backend'.

    Could not find any Cake files

    Detecting projects in '/home/fergalm/dev/myproj/myproj-backend/myproj-backend.sln'.

    Queue project update for '/home/fergalm/dev/myproj/myproj-backend/myproj-api/myproj-api.csproj'

    Queue project update for '/home/fergalm/dev/myproj/myproj-backend/myproj-data/myproj-data.csproj'

    Queue project update for '/home/fergalm/dev/myproj/myproj-backend/myproj-common/myproj-common.csproj'

    Queue project update for '/home/fergalm/dev/myproj/myproj-backend/myproj-jobs/myproj-jobs.csproj'

    Detecting CSX files in '/home/fergalm/dev/myproj/myproj-backend'.

    Could not find any CSX files

    Invoking Workspace Options Provider: OmniSharp.Roslyn.CSharp.Services.CSharpFormattingWorkspaceOptionsProvider, Order: 0

    Loading project: /home/fergalm/dev/myproj/myproj-backend/myproj-api/myproj-api.csproj

    Invoking Workspace Options Provider: OmniSharp.Roslyn.CSharp.Services.RenameWorkspaceOptionsProvider, Order: 100

    Invoking Workspace Options Provider: OmniSharp.Roslyn.CSharp.Services.EditorConfigWorkspaceOptionsProvider, Order: 200

    Configuration finished.

    Omnisharp server running using Stdio at location '/home/fergalm/dev/myproj/myproj-backend' on host 9878.

    Failed to load project file '/home/fergalm/dev/myproj/myproj-backend/myproj-api/myproj-api.csproj'.

/home/fergalm/dev/myproj/myproj-backend/myproj-api/myproj-api.csproj(1,1)
Microsoft.Build.Exceptions.InvalidProjectFileException: The imported project "/usr/lib/mono/xbuild/15.0/Microsoft.Common.props" was not found. Confirm that the path in the  declaration is correct, and that the file exists on disk.  /usr/share/dotnet/sdk/3.0.100/Sdks/Microsoft.NET.Sdk/Sdk/Sdk.props
at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject (System.String errorSubCategoryResourceName, Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, System.Object[] args) [0x00040] in :0
at Microsoft.Build.Shared.ProjectErrorUtilities.VerifyThrowInvalidProject[T1] (System.Boolean condition, System.String errorSubCategoryResourceName, Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, T1 arg0) [0x00003] in :0
at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject[T1] (Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, T1 arg0) [0x00000] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].ExpandAndLoadImportsFromUnescapedImportExpression (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement, System.String unescapedExpression, System.Boolean throwOnFileNotExistsError, System.Collections.Generic.List1[Microsoft.Build.Construction.ProjectRootElement]& imports) [0x0060f] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].ExpandAndLoadImportsFromUnescapedImportExpressionConditioned (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement, System.Collections.Generic.List1[Microsoft.Build.Construction.ProjectRootElement]& projects, Microsoft.Build.BackEnd.SdkResolution.SdkResult& sdkResult, System.Boolean throwOnFileNotExistsError) [0x00268] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].ExpandAndLoadImports (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement, Microsoft.Build.BackEnd.SdkResolution.SdkResult& sdkResult) [0x00027] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].EvaluateImportElement (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement) [0x0000d] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].PerformDepthFirstPass (Microsoft.Build.Construction.ProjectRootElement currentProjectOrImport) [0x00209] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].EvaluateImportElement (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement) [0x00040] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].PerformDepthFirstPass (Microsoft.Build.Construction.ProjectRootElement currentProjectOrImport) [0x00209] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].EvaluateImportElement (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement) [0x00040] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].PerformDepthFirstPass (Microsoft.Build.Construction.ProjectRootElement currentProjectOrImport) [0x000e6] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].Evaluate (Microsoft.Build.BackEnd.Logging.ILoggingService loggingService, Microsoft.Build.Framework.BuildEventContext buildEventContext) [0x0011c] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].Evaluate (Microsoft.Build.Evaluation.IEvaluatorData4[P,I,M,D] data, Microsoft.Build.Construction.ProjectRootElement root, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, System.Int32 maxNodeCount, Microsoft.Build.Collections.PropertyDictionary1[T] environmentProperties, Microsoft.Build.BackEnd.Logging.ILoggingService loggingService, Microsoft.Build.Evaluation.IItemFactory2[S,T] itemFactory, Microsoft.Build.Evaluation.IToolsetProvider toolsetProvider, Microsoft.Build.Evaluation.ProjectRootElementCache projectRootElementCache, Microsoft.Build.Framework.BuildEventContext buildEventContext, Microsoft.Build.BackEnd.SdkResolution.ISdkResolverService sdkResolverService, System.Int32 submissionId, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext, System.Boolean interactive) [0x0002f] in :0
at Microsoft.Build.Evaluation.Project.Reevaluate (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x0005e] in :0
at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00035] in :0
at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00000] in :0
at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00007] in :0
at Microsoft.Build.Evaluation.Project.Initialize (System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, System.String subToolsetVersion, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00126] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, System.String subToolsetVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00093] in :0
at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, System.String subToolsetVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x00000] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x00000] in :0
at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection) [0x00000] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.ProjectCollection.LoadProject (System.String fileName, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion) [0x000f7] in :0
at Microsoft.Build.Evaluation.ProjectCollection.LoadProject (System.String fileName, System.String toolsVersion) [0x00000] in :0
at OmniSharp.MSBuild.ProjectLoader.EvaluateProjectFileCore (System.String filePath) [0x0003f] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0
at OmniSharp.MSBuild.ProjectLoader.BuildProject (System.String filePath) [0x0000d] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0
at OmniSharp.MSBuild.ProjectFile.ProjectFileInfo.Load (System.String filePath, OmniSharp.MSBuild.ProjectIdInfo projectIdInfo, OmniSharp.MSBuild.ProjectLoader loader) [0x00015] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0
at OmniSharp.MSBuild.ProjectManager+<>c__DisplayClass29_0.b__0 () [0x00000] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0
at (wrapper delegate-invoke) System.Func1[System.ValueTuple3[OmniSharp.MSBuild.ProjectFile.ProjectFileInfo,System.Collections.Immutable.ImmutableArray1[OmniSharp.MSBuild.Logging.MSBuildDiagnostic],OmniSharp.MSBuild.Notification.ProjectLoadedEventArgs]].invoke_TResult()   at OmniSharp.MSBuild.ProjectManager.LoadOrReloadProject (System.String projectFilePath, System.Func1[TResult] loader) [0x0001b] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0
    Loading project: /home/fergalm/dev/myproj/myproj-backend/myproj-data/myproj-data.csproj

    Failed to load project file '/home/fergalm/dev/myproj/myproj-backend/myproj-data/myproj-data.csproj'.

/home/fergalm/dev/myproj/myproj-backend/myproj-data/myproj-data.csproj(1,1)
Microsoft.Build.Exceptions.InvalidProjectFileException: The imported project "/usr/lib/mono/xbuild/15.0/Microsoft.Common.props" was not found. Confirm that the path in the  declaration is correct, and that the file exists on disk.  /usr/share/dotnet/sdk/3.0.100/Sdks/Microsoft.NET.Sdk/Sdk/Sdk.props
at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject (System.String errorSubCategoryResourceName, Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, System.Object[] args) [0x00040] in :0
at Microsoft.Build.Shared.ProjectErrorUtilities.VerifyThrowInvalidProject[T1] (System.Boolean condition, System.String errorSubCategoryResourceName, Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, T1 arg0) [0x00003] in :0
at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject[T1] (Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, T1 arg0) [0x00000] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].ExpandAndLoadImportsFromUnescapedImportExpression (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement, System.String unescapedExpression, System.Boolean throwOnFileNotExistsError, System.Collections.Generic.List1[Microsoft.Build.Construction.ProjectRootElement]& imports) [0x0060f] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].ExpandAndLoadImportsFromUnescapedImportExpressionConditioned (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement, System.Collections.Generic.List1[Microsoft.Build.Construction.ProjectRootElement]& projects, Microsoft.Build.BackEnd.SdkResolution.SdkResult& sdkResult, System.Boolean throwOnFileNotExistsError) [0x00268] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].ExpandAndLoadImports (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement, Microsoft.Build.BackEnd.SdkResolution.SdkResult& sdkResult) [0x00027] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].EvaluateImportElement (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement) [0x0000d] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].PerformDepthFirstPass (Microsoft.Build.Construction.ProjectRootElement currentProjectOrImport) [0x00209] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].EvaluateImportElement (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement) [0x00040] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].PerformDepthFirstPass (Microsoft.Build.Construction.ProjectRootElement currentProjectOrImport) [0x000e6] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].Evaluate (Microsoft.Build.BackEnd.Logging.ILoggingService loggingService, Microsoft.Build.Framework.BuildEventContext buildEventContext) [0x0011c] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].Evaluate (Microsoft.Build.Evaluation.IEvaluatorData4[P,I,M,D] data, Microsoft.Build.Construction.ProjectRootElement root, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, System.Int32 maxNodeCount, Microsoft.Build.Collections.PropertyDictionary1[T] environmentProperties, Microsoft.Build.BackEnd.Logging.ILoggingService loggingService, Microsoft.Build.Evaluation.IItemFactory2[S,T] itemFactory, Microsoft.Build.Evaluation.IToolsetProvider toolsetProvider, Microsoft.Build.Evaluation.ProjectRootElementCache projectRootElementCache, Microsoft.Build.Framework.BuildEventContext buildEventContext, Microsoft.Build.BackEnd.SdkResolution.ISdkResolverService sdkResolverService, System.Int32 submissionId, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext, System.Boolean interactive) [0x0002f] in :0
at Microsoft.Build.Evaluation.Project.Reevaluate (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x0005e] in :0
at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00035] in :0
at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00000] in :0
at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00007] in :0
at Microsoft.Build.Evaluation.Project.Initialize (System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, System.String subToolsetVersion, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00126] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, System.String subToolsetVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00093] in :0
at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, System.String subToolsetVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x00000] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x00000] in :0
at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection) [0x00000] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.ProjectCollection.LoadProject (System.String fileName, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion) [0x000f7] in :0
at Microsoft.Build.Evaluation.ProjectCollection.LoadProject (System.String fileName, System.String toolsVersion) [0x00000] in :0
at OmniSharp.MSBuild.ProjectLoader.EvaluateProjectFileCore (System.String filePath) [0x0003f] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0
at OmniSharp.MSBuild.ProjectLoader.BuildProject (System.String filePath) [0x0000d] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0
at OmniSharp.MSBuild.ProjectFile.ProjectFileInfo.Load (System.String filePath, OmniSharp.MSBuild.ProjectIdInfo projectIdInfo, OmniSharp.MSBuild.ProjectLoader loader) [0x00015] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0
at OmniSharp.MSBuild.ProjectManager+<>c__DisplayClass29_0.b__0 () [0x00000] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0
at (wrapper delegate-invoke) System.Func1[System.ValueTuple3[OmniSharp.MSBuild.ProjectFile.ProjectFileInfo,System.Collections.Immutable.ImmutableArray1[OmniSharp.MSBuild.Logging.MSBuildDiagnostic],OmniSharp.MSBuild.Notification.ProjectLoadedEventArgs]].invoke_TResult()   at OmniSharp.MSBuild.ProjectManager.LoadOrReloadProject (System.String projectFilePath, System.Func1[TResult] loader) [0x0001b] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0
    Loading project: /home/fergalm/dev/myproj/myproj-backend/myproj-common/myproj-common.csproj

    Failed to load project file '/home/fergalm/dev/myproj/myproj-backend/myproj-common/myproj-common.csproj'.

/home/fergalm/dev/myproj/myproj-backend/myproj-common/myproj-common.csproj(1,1)
Microsoft.Build.Exceptions.InvalidProjectFileException: The imported project "/usr/lib/mono/xbuild/15.0/Microsoft.Common.props" was not found. Confirm that the path in the  declaration is correct, and that the file exists on disk.  /usr/share/dotnet/sdk/3.0.100/Sdks/Microsoft.NET.Sdk/Sdk/Sdk.props
at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject (System.String errorSubCategoryResourceName, Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, System.Object[] args) [0x00040] in :0
at Microsoft.Build.Shared.ProjectErrorUtilities.VerifyThrowInvalidProject[T1] (System.Boolean condition, System.String errorSubCategoryResourceName, Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, T1 arg0) [0x00003] in :0
at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject[T1] (Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, T1 arg0) [0x00000] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].ExpandAndLoadImportsFromUnescapedImportExpression (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement, System.String unescapedExpression, System.Boolean throwOnFileNotExistsError, System.Collections.Generic.List1[Microsoft.Build.Construction.ProjectRootElement]& imports) [0x0060f] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].ExpandAndLoadImportsFromUnescapedImportExpressionConditioned (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement, System.Collections.Generic.List1[Microsoft.Build.Construction.ProjectRootElement]& projects, Microsoft.Build.BackEnd.SdkResolution.SdkResult& sdkResult, System.Boolean throwOnFileNotExistsError) [0x00268] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].ExpandAndLoadImports (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement, Microsoft.Build.BackEnd.SdkResolution.SdkResult& sdkResult) [0x00027] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].EvaluateImportElement (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement) [0x0000d] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].PerformDepthFirstPass (Microsoft.Build.Construction.ProjectRootElement currentProjectOrImport) [0x00209] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].EvaluateImportElement (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement) [0x00040] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].PerformDepthFirstPass (Microsoft.Build.Construction.ProjectRootElement currentProjectOrImport) [0x000e6] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].Evaluate (Microsoft.Build.BackEnd.Logging.ILoggingService loggingService, Microsoft.Build.Framework.BuildEventContext buildEventContext) [0x0011c] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].Evaluate (Microsoft.Build.Evaluation.IEvaluatorData4[P,I,M,D] data, Microsoft.Build.Construction.ProjectRootElement root, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, System.Int32 maxNodeCount, Microsoft.Build.Collections.PropertyDictionary1[T] environmentProperties, Microsoft.Build.BackEnd.Logging.ILoggingService loggingService, Microsoft.Build.Evaluation.IItemFactory2[S,T] itemFactory, Microsoft.Build.Evaluation.IToolsetProvider toolsetProvider, Microsoft.Build.Evaluation.ProjectRootElementCache projectRootElementCache, Microsoft.Build.Framework.BuildEventContext buildEventContext, Microsoft.Build.BackEnd.SdkResolution.ISdkResolverService sdkResolverService, System.Int32 submissionId, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext, System.Boolean interactive) [0x0002f] in :0
at Microsoft.Build.Evaluation.Project.Reevaluate (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x0005e] in :0
at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00035] in :0
at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00000] in :0
at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00007] in :0
at Microsoft.Build.Evaluation.Project.Initialize (System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, System.String subToolsetVersion, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00126] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, System.String subToolsetVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00093] in :0
at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, System.String subToolsetVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x00000] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x00000] in :0
at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection) [0x00000] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.ProjectCollection.LoadProject (System.String fileName, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion) [0x000f7] in :0
at Microsoft.Build.Evaluation.ProjectCollection.LoadProject (System.String fileName, System.String toolsVersion) [0x00000] in :0
at OmniSharp.MSBuild.ProjectLoader.EvaluateProjectFileCore (System.String filePath) [0x0003f] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0
at OmniSharp.MSBuild.ProjectLoader.BuildProject (System.String filePath) [0x0000d] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0
at OmniSharp.MSBuild.ProjectFile.ProjectFileInfo.Load (System.String filePath, OmniSharp.MSBuild.ProjectIdInfo projectIdInfo, OmniSharp.MSBuild.ProjectLoader loader) [0x00015] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0
at OmniSharp.MSBuild.ProjectManager+<>c__DisplayClass29_0.b__0 () [0x00000] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0
at (wrapper delegate-invoke) System.Func1[System.ValueTuple3[OmniSharp.MSBuild.ProjectFile.ProjectFileInfo,System.Collections.Immutable.ImmutableArray1[OmniSharp.MSBuild.Logging.MSBuildDiagnostic],OmniSharp.MSBuild.Notification.ProjectLoadedEventArgs]].invoke_TResult()   at OmniSharp.MSBuild.ProjectManager.LoadOrReloadProject (System.String projectFilePath, System.Func1[TResult] loader) [0x0001b] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0
    Loading project: /home/fergalm/dev/myproj/myproj-backend/myproj-jobs/myproj-jobs.csproj

    Failed to load project file '/home/fergalm/dev/myproj/myproj-backend/myproj-jobs/myproj-jobs.csproj'.

/home/fergalm/dev/myproj/myproj-backend/myproj-jobs/myproj-jobs.csproj(1,1)
Microsoft.Build.Exceptions.InvalidProjectFileException: The imported project "/usr/lib/mono/xbuild/15.0/Microsoft.Common.props" was not found. Confirm that the path in the  declaration is correct, and that the file exists on disk.  /usr/share/dotnet/sdk/3.0.100/Sdks/Microsoft.NET.Sdk/Sdk/Sdk.props
at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject (System.String errorSubCategoryResourceName, Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, System.Object[] args) [0x00040] in :0
at Microsoft.Build.Shared.ProjectErrorUtilities.VerifyThrowInvalidProject[T1] (System.Boolean condition, System.String errorSubCategoryResourceName, Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, T1 arg0) [0x00003] in :0
at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject[T1] (Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, T1 arg0) [0x00000] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].ExpandAndLoadImportsFromUnescapedImportExpression (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement, System.String unescapedExpression, System.Boolean throwOnFileNotExistsError, System.Collections.Generic.List1[Microsoft.Build.Construction.ProjectRootElement]& imports) [0x0060f] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].ExpandAndLoadImportsFromUnescapedImportExpressionConditioned (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement, System.Collections.Generic.List1[Microsoft.Build.Construction.ProjectRootElement]& projects, Microsoft.Build.BackEnd.SdkResolution.SdkResult& sdkResult, System.Boolean throwOnFileNotExistsError) [0x00268] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].ExpandAndLoadImports (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement, Microsoft.Build.BackEnd.SdkResolution.SdkResult& sdkResult) [0x00027] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].EvaluateImportElement (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement) [0x0000d] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].PerformDepthFirstPass (Microsoft.Build.Construction.ProjectRootElement currentProjectOrImport) [0x00209] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].EvaluateImportElement (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement) [0x00040] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].PerformDepthFirstPass (Microsoft.Build.Construction.ProjectRootElement currentProjectOrImport) [0x00209] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].EvaluateImportElement (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement) [0x00040] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].PerformDepthFirstPass (Microsoft.Build.Construction.ProjectRootElement currentProjectOrImport) [0x000e6] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].Evaluate (Microsoft.Build.BackEnd.Logging.ILoggingService loggingService, Microsoft.Build.Framework.BuildEventContext buildEventContext) [0x0011c] in :0
at Microsoft.Build.Evaluation.Evaluator4[P,I,M,D].Evaluate (Microsoft.Build.Evaluation.IEvaluatorData4[P,I,M,D] data, Microsoft.Build.Construction.ProjectRootElement root, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, System.Int32 maxNodeCount, Microsoft.Build.Collections.PropertyDictionary1[T] environmentProperties, Microsoft.Build.BackEnd.Logging.ILoggingService loggingService, Microsoft.Build.Evaluation.IItemFactory2[S,T] itemFactory, Microsoft.Build.Evaluation.IToolsetProvider toolsetProvider, Microsoft.Build.Evaluation.ProjectRootElementCache projectRootElementCache, Microsoft.Build.Framework.BuildEventContext buildEventContext, Microsoft.Build.BackEnd.SdkResolution.ISdkResolverService sdkResolverService, System.Int32 submissionId, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext, System.Boolean interactive) [0x0002f] in :0
at Microsoft.Build.Evaluation.Project.Reevaluate (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x0005e] in :0
at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00035] in :0
at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00000] in :0
at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00007] in :0
at Microsoft.Build.Evaluation.Project.Initialize (System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, System.String subToolsetVersion, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00126] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, System.String subToolsetVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00093] in :0
at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, System.String subToolsetVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x00000] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x00000] in :0
at Microsoft.Build.Evaluation.Project..ctor (System.String projectFile, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion, Microsoft.Build.Evaluation.ProjectCollection projectCollection) [0x00000] in <b695b16788dd418cbe8b4d98f7a92ff3>:0    at Microsoft.Build.Evaluation.ProjectCollection.LoadProject (System.String fileName, System.Collections.Generic.IDictionary2[TKey,TValue] globalProperties, System.String toolsVersion) [0x000f7] in :0
at Microsoft.Build.Evaluation.ProjectCollection.LoadProject (System.String fileName, System.String toolsVersion) [0x00000] in :0
at OmniSharp.MSBuild.ProjectLoader.EvaluateProjectFileCore (System.String filePath) [0x0003f] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0
at OmniSharp.MSBuild.ProjectLoader.BuildProject (System.String filePath) [0x0000d] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0
at OmniSharp.MSBuild.ProjectFile.ProjectFileInfo.Load (System.String filePath, OmniSharp.MSBuild.ProjectIdInfo projectIdInfo, OmniSharp.MSBuild.ProjectLoader loader) [0x00015] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0
at OmniSharp.MSBuild.ProjectManager+<>c__DisplayClass29_0.b__0 () [0x00000] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0
at (wrapper delegate-invoke) System.Func1[System.ValueTuple3[OmniSharp.MSBuild.ProjectFile.ProjectFileInfo,System.Collections.Immutable.ImmutableArray1[OmniSharp.MSBuild.Logging.MSBuildDiagnostic],OmniSharp.MSBuild.Notification.ProjectLoadedEventArgs]].invoke_TResult()   at OmniSharp.MSBuild.ProjectManager.LoadOrReloadProject (System.String projectFilePath, System.Func1[TResult] loader) [0x0001b] in <4d39b1cf1ca84cccbd4059b400c1cde5>:0
    Attempted to update project that is not loaded: /home/fergalm/dev/myproj/myproj-backend/myproj-api/myproj-api.csproj

    Attempted to update project that is not loaded: /home/fergalm/dev/myproj/myproj-backend/myproj-data/myproj-data.csproj

    Attempted to update project that is not loaded: /home/fergalm/dev/myproj/myproj-backend/myproj-common/myproj-common.csproj

    Attempted to update project that is not loaded: /home/fergalm/dev/myproj/myproj-backend/myproj-jobs/myproj-jobs.csproj

so according to that log it seems like you have mono installation that is really old (?) or only has xbuild but no msbuild.
since it doesn't get discovered with the msbuild discovery and instead surfaces with xbuild
which mono is that? is it available on the path with the mono command for OmniSharp to call into (doesn't seem so from your log).
is there a reason mono is installed this way?
I'd start by cleaning up this mono installation and install again mono-devel package from apt

mono version is 5.18.0.240+dfsg-2ubuntu2
It is on my path.
It is installed from the standard mono-complete disco apt repo.
I installed it this way because I didn't know any better?

I removed & purged mono-* and reinstalled, still the same I'm afraid.

mono-complete is the superset of mono-devel so it's fine. However OmniSharp now requires at least Mono 6.4.0 - it would be best to update the installation to that version (that's actually the latest stable). The problem is that even if OmiSharp runs standalone mode and doesn't use global mono, some of the msbuild extension paths and such will still be inherited from mono therefore if it's an old version things might start breaking down.

AAAARGH! Of course, I'm so sorry, I should have known better. Installed mono from the mono apt repo at https://www.mono-project.com/download/stable/ and all is good again!!
Thanks so much for your help, Filip!

ah that's great to hear - thanks 👍

Also a word of explanation - the reason why latest Omnisharp suddenly requires Mono 6.4.0 is that this is the version of Mono that supports .NET Core 3.0.
Unfortunately the rules of minimum Mono versions are not very well enforced in the code at the moment, so OmniSharp can still pick up an older one and that results in potential problems.

Just to add another note for future visitors, this just re-occurred for me again but removing all bin & obj folders in my solution directory and restarting vscode sorted it out.

Not so far in the future as @fergalmoran, but also for future visitors  - but I've had the same problem. I removed mono ( and also nuget, which seemed to depend on mono) and suddenly VS code is working.
I'm running Arch and the official MS VS-code from the aur.

This occurred to me on macOS and the comment of

On macOS uninstalling mono and re-installing

worked for me. The mono website has instructions on how to properly uninstall mono on macOS.

authors: DustinCampbell ErikFeeley Fishrock123 MarkusAmshove PeteX agc93 akshita31 arcooke curtisy1 dwarburt fergalmoran filipw hrobertson jaccarmac kpbarrow mzgnr robvanpamel rstrube sekseason soccermitchy

repo: OmniSharp/omnisharp-vscode