vscode-csharp: Omnisharp InvalidProjectFileException not fixed by 1.16.1

Note: This is probably related to #2509. I was asked by @rchande to report this specific case as a new issue, since the 1.16.1 release did fix the issue for most people, but not for me. Installing version 1.15.2 of the extension does not give the problem.

Environment data

uname -a output:

Linux gijsbertdebian 4.9.0-8-amd64 #1 SMP Debian 4.9.110-3+deb9u4 (2018-08-21) x86_64 GNU/Linux

dotnet --info output:.

NET Core SDK (reflecting any global.json):
 Version:   2.1.402
 Commit:    3599f217f4

Runtime Environment:
 OS Name:     debian
 OS Version:  9
 OS Platform: Linux
 RID:         debian.9-x64
 Base Path:   /usr/share/dotnet/sdk/2.1.402/

Host (useful for support):
  Version: 2.1.4
  Commit:  85255dde3e

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

.NET Core runtimes installed:
  Microsoft.AspNetCore.All 2.1.4 [/usr/share/dotnet/shared/Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.4 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.1.4 [/usr/share/dotnet/shared/Microsoft.NETCore.App]

To install additional .NET Core runtimes or SDKs:
  https://aka.ms/dotnet-download

VS Code version:

1.27.2
f46c4c469d6e6d8c46f268d1553c5dc4b475840f
x64

C# Extension version: 1.16.1

Steps to reproduce

Open project folder

Expected behavior

Project loads, Omnisharp works

Actual behavior

Project loads, Omnisharp throws InvalidProjectFileException (for every project file in the project) Omnisharp functionality does not initialise and cannot be used.

Omnisharp log

Note: This is a slightly sanitised version of the log, I have 5 sub-projects that throw the identical error. I reduced this to just one sub-project Project.T in this log.

Starting OmniSharp server at 14/09/2018, 10:06:44
    Target: /home/user/workspace/Project/Project.sln

OmniSharp server started.
    Path: /home/user/.vscode/extensions/ms-vscode.csharp-1.16.1/.omnisharp/1.32.5/run
    PID: 7928

[info]: OmniSharp.Stdio.Host
        Starting OmniSharp on debian 9.0 (x64)
[info]: OmniSharp.Services.DotNetCliService
        DotNetPath set to dotnet
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Located 1 MSBuild instance(s)
            1: StandAlone 15.0 - "/home/user/.vscode/extensions/ms-vscode.csharp-1.16.1/.omnisharp/1.32.5/omnisharp/msbuild/15.0/Bin"
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        MSBUILD_EXE_PATH environment variable set to '/home/user/.vscode/extensions/ms-vscode.csharp-1.16.1/.omnisharp/1.32.5/omnisharp/msbuild/15.0/Bin/MSBuild.dll'
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Registered MSBuild instance: StandAlone 15.0 - "/home/user/.vscode/extensions/ms-vscode.csharp-1.16.1/.omnisharp/1.32.5/omnisharp/msbuild/15.0/Bin"
            MSBuildExtensionsPath = /home/user/.vscode/extensions/ms-vscode.csharp-1.16.1/.omnisharp/1.32.5/omnisharp/msbuild
            BypassFrameworkInstallChecks = true
            CscToolPath = /home/user/.vscode/extensions/ms-vscode.csharp-1.16.1/.omnisharp/1.32.5/omnisharp/msbuild/15.0/Bin/Roslyn
            CscToolExe = csc.exe
            MSBuildToolsPath = /home/user/.vscode/extensions/ms-vscode.csharp-1.16.1/.omnisharp/1.32.5/omnisharp/msbuild/15.0/Bin
            TargetFrameworkRootPath = /usr/lib/mono/xbuild-frameworks
[info]: OmniSharp.Cake.CakeProjectSystem
        Detecting Cake files in '/home/user/workspace/Project'.
[info]: OmniSharp.Cake.CakeProjectSystem
        Could not find any Cake files
[info]: OmniSharp.WorkspaceInitializer
        Project system 'OmniSharp.DotNet.DotNetProjectSystem' is disabled in the configuration.
[info]: OmniSharp.MSBuild.ProjectSystem
        Detecting projects in '/home/user/workspace/Project/Project.sln'.
[info]: OmniSharp.MSBuild.ProjectManager
        Queue project update for '/home/user/workspace/Project/Project.T/Project.T.csproj'
[info]: OmniSharp.Script.ScriptProjectSystem
        Detecting CSX files in '/home/user/workspace/Project'.
[info]: OmniSharp.Script.ScriptProjectSystem
        Could not find any CSX files
[info]: OmniSharp.WorkspaceInitializer
        Invoking Workspace Options Provider: OmniSharp.Roslyn.CSharp.Services.CSharpWorkspaceOptionsProvider
[info]: OmniSharp.WorkspaceInitializer
        Configuration finished.
[info]: OmniSharp.Stdio.Host
        Omnisharp server running using Stdio at location '/home/user/workspace/Project' on host 7621.
[info]: OmniSharp.MSBuild.ProjectManager
        Loading project: /home/user/workspace/Project/Project.T/Project.T.csproj
[warn]: OmniSharp.MSBuild.ProjectManager
        Failed to load project file '/home/user/workspace/Project/Project.T/Project.T.csproj'.
/home/user/workspace/Project/Project.T/Project.T.csproj(1,1)
Microsoft.Build.Exceptions.InvalidProjectFileException: The SDK 'Microsoft.NET.Sdk.Web' specified could not be found.  /home/user/workspace/Project/Project.T/Project.T.csproj
  at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject (System.String errorSubCategoryResourceName, Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, System.Object[] args) [0x00040] in <2338fdb301034c1d9c6b95e564d514b0>: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 <2338fdb301034c1d9c6b95e564d514b0>:0 
  at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject[T1] (Microsoft.Build.Shared.IElementLocation elementLocation, System.String resourceName, T1 arg0) [0x00000] in <2338fdb301034c1d9c6b95e564d514b0>: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) [0x00254] in <2338fdb301034c1d9c6b95e564d514b0>:0 
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].ExpandAndLoadImports (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement) [0x00024] in <2338fdb301034c1d9c6b95e564d514b0>:0 
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].EvaluateImportElement (System.String directoryOfImportingFile, Microsoft.Build.Construction.ProjectImportElement importElement) [0x0000d] in <2338fdb301034c1d9c6b95e564d514b0>:0 
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].PerformDepthFirstPass (Microsoft.Build.Construction.ProjectRootElement currentProjectOrImport) [0x000e6] in <2338fdb301034c1d9c6b95e564d514b0>:0 
  at Microsoft.Build.Evaluation.Evaluator`4[P,I,M,D].Evaluate (Microsoft.Build.BackEnd.Logging.ILoggingService loggingService, Microsoft.Build.Framework.BuildEventContext buildEventContext) [0x00103] in <2338fdb301034c1d9c6b95e564d514b0>: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.ISdkResolverService sdkResolverService, System.Int32 submissionId, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x0001a] in <2338fdb301034c1d9c6b95e564d514b0>:0 
  at Microsoft.Build.Evaluation.Project.Reevaluate (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x0004c] in <2338fdb301034c1d9c6b95e564d514b0>:0 
  at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation, Microsoft.Build.Evaluation.ProjectLoadSettings loadSettings) [0x00034] in <2338fdb301034c1d9c6b95e564d514b0>:0 
  at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.BackEnd.Logging.ILoggingService loggingServiceForEvaluation) [0x00000] in <2338fdb301034c1d9c6b95e564d514b0>:0 
  at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary (Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00023] in <2338fdb301034c1d9c6b95e564d514b0>: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, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x00126] in <2338fdb301034c1d9c6b95e564d514b0>: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, Microsoft.Build.Evaluation.Context.EvaluationContext evaluationContext) [0x0009e] in <2338fdb301034c1d9c6b95e564d514b0>: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) [0x00000] in <2338fdb301034c1d9c6b95e564d514b0>: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 <2338fdb301034c1d9c6b95e564d514b0>: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 <2338fdb301034c1d9c6b95e564d514b0>:0 
  at Microsoft.Build.Evaluation.ProjectCollection.LoadProject (System.String fileName, System.Collections.Generic.IDictionary`2[TKey,TValue] globalProperties, System.String toolsVersion) [0x000f5] in <2338fdb301034c1d9c6b95e564d514b0>:0 
  at Microsoft.Build.Evaluation.ProjectCollection.LoadProject (System.String fileName, System.String toolsVersion) [0x00000] in <2338fdb301034c1d9c6b95e564d514b0>:0 
  at OmniSharp.MSBuild.ProjectLoader.EvaluateProjectFileCore (System.String filePath) [0x0003e] in <99f3a3b619ce4010a7d6d489ffd5bcf1>:0 
  at OmniSharp.MSBuild.ProjectLoader.BuildProject (System.String filePath) [0x0000d] in <99f3a3b619ce4010a7d6d489ffd5bcf1>:0 
  at OmniSharp.MSBuild.ProjectFile.ProjectFileInfo.Load (System.String filePath, OmniSharp.MSBuild.ProjectLoader loader) [0x00015] in <99f3a3b619ce4010a7d6d489ffd5bcf1>:0 
  at OmniSharp.MSBuild.ProjectManager+<>c__DisplayClass25_0.<LoadProject>b__0 () [0x00000] in <99f3a3b619ce4010a7d6d489ffd5bcf1>:0 
  at (wrapper delegate-invoke) System.Func`1[System.ValueTuple`3[OmniSharp.MSBuild.ProjectFile.ProjectFileInfo,System.Collections.Immutable.ImmutableArray`1[OmniSharp.MSBuild.Logging.MSBuildDiagnostic],OmniSharp.MSBuild.Notification.ProjectLoadedEventArgs]].invoke_TResult()
  at OmniSharp.MSBuild.ProjectManager.LoadOrReloadProject (System.String projectFilePath, System.Func`1[TResult] loader) [0x0001b] in <99f3a3b619ce4010a7d6d489ffd5bcf1>:0
 
[fail]: OmniSharp.MSBuild.ProjectManager
      Attemped to update project that is not loaded: /home/gijsbert/workspace/Project/Project.T/Project.T.csproj