System.IO.FileLoadException: Could not load file or assembly 'System.Collections.Immutable'

Environment data

dotnet --info output:

.NET Core SDK (reflecting any global.json):
 Version:   2.1.401
 Commit:    91b1c13032

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.17134
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\2.1.401\

Host (useful for support):
  Version: 2.1.3
  Commit:  124038c13e

.NET Core SDKs installed:
  1.0.0-preview2-003131 [C:\Program Files\dotnet\sdk]
  2.1.4 [C:\Program Files\dotnet\sdk]
  2.1.103 [C:\Program Files\dotnet\sdk]
  2.1.200 [C:\Program Files\dotnet\sdk]
  2.1.201 [C:\Program Files\dotnet\sdk]
  2.1.202 [C:\Program Files\dotnet\sdk]
  2.1.400 [C:\Program Files\dotnet\sdk]
  2.1.401 [C:\Program Files\dotnet\sdk]

.NET Core runtimes installed:
  Microsoft.AspNetCore.All 2.1.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.3 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.3 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 1.0.1 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.0.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.0.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.0.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.0.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.2 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.3 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]

VS Code version:

Version: 1.26.1
Commit: 493869ee8e8a846b0855873886fc79d480d342de
Date: 2018-08-16T18:38:57.434Z
Electron: 2.0.5
Chrome: 61.0.3163.100
Node.js: 8.9.3
V8: 6.1.534.41
Architecture: x64

C# Extension version: 1.15.2

Steps to reproduce

1.

mkdir test
cd test
dotnet new console

2. Open folder in VS Code

Expected behavior

Working intellisense

Actual behavior

Getting this error in OmniSharp Log :

Starting OmniSharp server at 8/31/2018, 7:22:44 AM
    Target: c:\Temp\test

OmniSharp server started
    Path: C:\Users\zzz\.vscode\extensions\ms-vscode.csharp-1.15.2\.omnisharp\1.30.1\OmniSharp.exe
    PID: 25892

[info]: OmniSharp.Stdio.Host
        Starting OmniSharp on Windows 6.2.9200.0 (x64)
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Located 2 MSBuild instance(s)
            1: Visual Studio Professional 2017 15.8.28010.0 - "C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\15.0\Bin"
            2: StandAlone 15.0 - "C:\Users\zzz\.vscode\extensions\ms-vscode.csharp-1.15.2\.omnisharp\1.30.1\msbuild\15.0\Bin"
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Registered MSBuild instance: Visual Studio Professional 2017 15.8.28010.0 - "C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\15.0\Bin"
[info]: OmniSharp.Cake.CakeProjectSystem
        Detecting Cake files in 'c:\Temp\test'.
[info]: OmniSharp.Cake.CakeProjectSystem
        Could not find any Cake files
[info]: OmniSharp.DotNet.DotNetProjectSystem
        Initializing in c:\Temp\test
[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.ProjectSystem
        No solution files found in 'c:\Temp\test'
[info]: OmniSharp.MSBuild.ProjectManager
        Queue project update for 'c:\Temp\test\test.csproj'
[info]: OmniSharp.Script.ScriptProjectSystem
        Detecting CSX files in 'c:\Temp\test'.
[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 'c:\Temp\test' on host 29336.
[info]: OmniSharp.MSBuild.ProjectManager
        Loading project: c:\Temp\test\test.csproj
[warn]: OmniSharp.MSBuild.ProjectManager
        Failed to load project file 'c:\Temp\test\test.csproj'.
c:\Temp\test\test.csproj(1,1)
System.IO.FileLoadException: Could not load file or assembly 'System.Collections.Immutable, Version=1.2.3.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)
File name: 'System.Collections.Immutable, Version=1.2.3.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'
   at Microsoft.Build.Evaluation.Context.EvaluationContext..ctor(SharingPolicy policy)
   at Microsoft.Build.Evaluation.Context.EvaluationContext.Create(SharingPolicy policy)
   at Microsoft.Build.Evaluation.Project.Reevaluate(ILoggingService loggingServiceForEvaluation, ProjectLoadSettings loadSettings, EvaluationContext evaluationContext)
   at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary(ILoggingService loggingServiceForEvaluation, ProjectLoadSettings loadSettings, EvaluationContext evaluationContext)
   at Microsoft.Build.Evaluation.Project.Initialize(IDictionary`2 globalProperties, String toolsVersion, String subToolsetVersion, ProjectLoadSettings loadSettings, EvaluationContext evaluationContext)
   at Microsoft.Build.Evaluation.Project..ctor(String projectFile, IDictionary`2 globalProperties, String toolsVersion, String subToolsetVersion, ProjectCollection projectCollection, ProjectLoadSettings loadSettings, EvaluationContext evaluationContext)
   at Microsoft.Build.Evaluation.ProjectCollection.LoadProject(String fileName, IDictionary`2 globalProperties, String toolsVersion)
   at OmniSharp.MSBuild.ProjectLoader.EvaluateProjectFileCore(String filePath)
   at OmniSharp.MSBuild.ProjectLoader.BuildProject(String filePath)
   at OmniSharp.MSBuild.ProjectFile.ProjectFileInfo.Load(String filePath, ProjectLoader loader)
   at OmniSharp.MSBuild.ProjectManager.LoadOrReloadProject(String projectFilePath, Func`1 loadFunc)

WRN: Assembly binding logging is turned OFF.
To enable assembly bind failure logging, set the registry value [HKLM\Software\Microsoft\Fusion!EnableLog] (DWORD) to 1.
Note: There is some performance penalty associated with assembly bind failure logging.
To turn this feature off, remove the registry value [HKLM\Software\Microsoft\Fusion!EnableLog].

[rchande]

It basically sounds like the version of VS that @f3rland has installed has upgraded to a new copy of System.Collections.Immutable that OmniSharp doesn’t have a binding redirect for. @f3rland Can you try setting the option “omnisharp.path” to “latest” and see if that helps? @akshita31 Alternatively, you can try upgrading to the latest internal build of VS 2017 and trying to reproduce this with the version of OmniSharp shipped with 15.2 of the extension (not the latest version).

[akshita31]

@f3rland Glad to know it worked. Thanks @rchande. I will close this issue now.