VSCode .Net Core MVC reports problems but Project Builds and Runs just fine

[mikemurphysmind]

Please paste the output from your clipboard## Issue Description ##

Steps to Reproduce

Expected Behavior

Actual Behavior

Logs

OmniSharp log

Post the output from Output-->OmniSharp log here

C# log

Post the output from Output-->C# here

Environment information

VSCode version: 1.50.1
C# Extension: 1.23.4

Mono Information

OmniSharp using global mono :6.4.0

Dotnet Information

.NET Core SDK (reflecting any global.json): Version: 3.1.402 Commit: 9b5de826fd

Runtime Environment:
OS Name: Mac OS X
OS Version: 10.15
OS Platform: Darwin
RID: osx.10.15-x64
Base Path: /usr/local/share/dotnet/sdk/3.1.402/

Host (useful for support):
Version: 3.1.8
Commit: 9c1330dedd

.NET Core SDKs installed:
3.0.100 [/usr/local/share/dotnet/sdk]
3.1.402 [/usr/local/share/dotnet/sdk]

.NET Core runtimes installed:
Microsoft.AspNetCore.App 3.0.0 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.8 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 2.1.13 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 3.0.0 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.8 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]

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

Visual Studio Code Extensions

Extension	Author	Version
azure-account	ms-vscode	0.9.3
azure-iot-toolkit	vsciot-vscode	2.16.4
azure-pipelines	ms-azure-devops	1.177.0
azure-storage-explorer	formulahendry	0.1.2
azurecli	ms-vscode	0.5.0
azurerm-vscode-tools	msazurermtools	0.13.0
csharp	ms-dotnettools	1.23.4
mssql	ms-mssql	1.9.0
prettier-vscode	esbenp	5.7.1
python	ms-python	2020.9.114305
rest-client	humao	0.24.3
vscode-ai	ms-toolsai	0.6.16
vscode-apimanagement	ms-azuretools	0.1.6
vscode-azureappservice	ms-azuretools	0.19.0
vscode-azurefunctions	ms-azuretools	1.0.0
vscode-azureresourcegroups	ms-azuretools	0.2.0
vscode-azurestorage	ms-azuretools	0.10.1
vscode-azurevirtualmachines	ms-azuretools	0.2.0
vscode-cosmosdb	ms-azuretools	0.15.0
vscode-css-peek	pranaygp	4.0.0
vscode-docker	ms-azuretools	1.7.0
vscode-dotnet-runtime	ms-dotnettools	0.1.2
vscode-node-azure-pack	ms-vscode	0.0.11
vscode-nuget-package-manager	jmrog	1.1.6
xml	DotJoshJohnson	2.5.1

These errors just started yesteday. Before this everything was fine.

To troubleshoot the issue, I created a new .Net Core MVC project using dotnet new mvc. I opened the project in vscode with no modifications. VSCode n OSX immediately showed the errors/problems. I opened this new project in VSCode on Windows. No errors.
On VSCode OSX I removed the C# extension and the errors disappeared. I reinstalled the C# extension and the errors returned.

Images showing issue

This only occurs in VSCode on OSX. VSCode on Windows does not exhibit this issue.

[Cooksauce]

I'm running into this same issue as well (also on macOS 10.15.7). Omnisharp Logs...

Razor Fail:

[info]: OmniSharp.MSBuild.ProjectManager
        Queue project update for '/path/to/Redacted.Project.csproj'
[info]: OmniSharp.MSBuild.ProjectManager
        Loading project: /path/to/Redacted.Project.csproj
[fail]: OmniSharp.MSBuild.ProjectLoader
        rzc generate exited with code 129.
[warn]: OmniSharp.MSBuild.ProjectManager
        Failed to load project file '/path/to/Redacted.Project.csproj'.
/path/to/Redacted.Project.csproj
/Library/Frameworks/Mono.framework/Versions/6.12.0/lib/mono/msbuild/Current/bin/Sdks/Microsoft.NET.Sdk.Razor/build/netstandard2.0/Microsoft.NET.Sdk.Razor.Component.targets(106,5): Error: rzc generate exited with code 129.

Host Exception

[fail]: OmniSharp.Stdio.Host
        ************  Response ************ 
{
  "Request_seq": 6614,
  "Command": "/v2/highlight",
  "Running": true,
  "Success": false,
  "Message": "\"System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.\\nParameter name: character\\n  at Microsoft.CodeAnalysis.Text.LinePosition..ctor (System.Int32 line, System.Int32 character) [0x00013] in <74e762f007514b0991a005183ec8dcb2>:0 \\n  at OmniSharp.Roslyn.CSharp.Services.SemanticHighlight.SemanticHighlightService.Handle (OmniSharp.Models.SemanticHighlight.SemanticHighlightRequest request) [0x00146] in <845c3087cc7d4530b36a8584d73f1c1d>:0 \\n  at OmniSharp.Endpoint.EndpointHandler`2[TRequest,TResponse].GetFirstNotEmptyResponseFromHandlers (OmniSharp.Endpoint.Exports.ExportHandler`2[TRequest,TResponse][] handlers, TRequest request) [0x00099] in <0b3dc7d6f0c8428682a86ac3f9663775>:0 \\n  at OmniSharp.Endpoint.EndpointHandler`2[TRequest,TResponse].HandleRequestForLanguage (System.String language, TRequest request, OmniSharp.Protocol.RequestPacket packet) [0x00163] in <0b3dc7d6f0c8428682a86ac3f9663775>:0 \\n  at OmniSharp.Endpoint.EndpointHandler`2[TRequest,TResponse].Process (OmniSharp.Protocol.RequestPacket packet, OmniSharp.Endpoint.LanguageModel model, Newtonsoft.Json.Linq.JToken requestObject) [0x0024b] in <0b3dc7d6f0c8428682a86ac3f9663775>:0 \\n  at OmniSharp.Stdio.Host.HandleRequest (System.String json, Microsoft.Extensions.Logging.ILogger logger) [0x000e7] in <0ff274924a1842faabf855aebc686508>:0 \"",
  "Body": null,
  "Seq": 7478,
  "Type": "response"
}
[fail]: OmniSharp.Stdio.Host
        ************  Response ************ 
{
  "Request_seq": 6617,
  "Command": "/v2/highlight",
  "Running": true,
  "Success": false,
  "Message": "\"System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.\\nParameter name: character\\n  at Microsoft.CodeAnalysis.Text.LinePosition..ctor (System.Int32 line, System.Int32 character) [0x00013] in <74e762f007514b0991a005183ec8dcb2>:0 \\n  at OmniSharp.Roslyn.CSharp.Services.SemanticHighlight.SemanticHighlightService.Handle (OmniSharp.Models.SemanticHighlight.SemanticHighlightRequest request) [0x00146] in <845c3087cc7d4530b36a8584d73f1c1d>:0 \\n  at OmniSharp.Endpoint.EndpointHandler`2[TRequest,TResponse].GetFirstNotEmptyResponseFromHandlers (OmniSharp.Endpoint.Exports.ExportHandler`2[TRequest,TResponse][] handlers, TRequest request) [0x00099] in <0b3dc7d6f0c8428682a86ac3f9663775>:0 \\n  at OmniSharp.Endpoint.EndpointHandler`2[TRequest,TResponse].HandleRequestForLanguage (System.String language, TRequest request, OmniSharp.Protocol.RequestPacket packet) [0x00163] in <0b3dc7d6f0c8428682a86ac3f9663775>:0 \\n  at OmniSharp.Endpoint.EndpointHandler`2[TRequest,TResponse].Process (OmniSharp.Protocol.RequestPacket packet, OmniSharp.Endpoint.LanguageModel model, Newtonsoft.Json.Linq.JToken requestObject) [0x0024b] in <0b3dc7d6f0c8428682a86ac3f9663775>:0 \\n  at OmniSharp.Stdio.Host.HandleRequest (System.String json, Microsoft.Extensions.Logging.ILogger logger) [0x000e7] in <0ff274924a1842faabf855aebc686508>:0 \"",
  "Body": null,
  "Seq": 7484,
  "Type": "response"
}

[breiter]

I think the problem is that the global mono is not compatible with the omnisharp that is embedded in the C# extension version 1.23.4.

Even if you have the latest stable 6.12.0.90 mono from https://www.mono-project.com/download/stable/, it doesn't work with this version of omnisharp. The good news is that the extension has its own embedded mono runtime and dependencies.

Uninstalling the global mono or setting the UseGlobalMono option for vscode in settings.json to "never" resolves the problem.

{    
  "omnisharp.useGlobalMono": "never"
}

I did some spelunking and while the mono binary that is embedded in the extension is 6.12.0.90, the msbuild engine is actually a preview that is 2 point releases newer than what is in the stable mono distribution. There may be other differences.

See also #4123 (comment)

[filipw]

Please set

{    
  "omnisharp.useGlobalMono": "never"
}

From the next version of the extension this will be the default option again (#4130)

With regards to Mono that is compatible with 3.1.402 SDK and .NET 5.0, see (and upvote) this issue mono/mono#20250 (comment). Without it there is not much else we can do to make global Mono work - in fact we manually build our own embedded Mono runtime that allows us to work around that.

[filipw]

@Cooksauce the Razor exception is something else, could you please open a new issue for this Error: rzc generate exited with code 129. problem? thanks!