OmniSharp unable to load project with Razor?

Environment data

dotnet --info output:

.NET SDK (reflecting any global.json):
 Version:   5.0.104
 Commit:    ca6b6acadb

Runtime Environment:
 OS Name:     arch
 OS Version:  
 OS Platform: Linux
 RID:         arch-x64
 Base Path:   /usr/share/dotnet/sdk/5.0.104/

Host (useful for support):
  Version: 5.0.0
  Commit:  cf258a14b7

.NET SDKs installed:
  3.1.112 [/usr/share/dotnet/sdk]
  5.0.104 [/usr/share/dotnet/sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 3.1.12 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.4 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 3.1.12 [/usr/share/dotnet/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.4 [/usr/share/dotnet/shared/Microsoft.NETCore.App]

VS Code version: 1.54.3 C# Extension version: 1.23.9

OmniSharp log

https://gist.github.com/ThomasAunvik/e4bb57c12445136458908ce370445096

Steps to reproduce

I am not sure, but my it seems like my project is using Razor library from netstandard2.0 which fails to load the project that is running on core 3.1.

Expected behavior

To omnisharp to load the project correctly.

Actual behavior

Intellisense and other stuff like autocomplete stops working at all, and failes to load the main project.

[warn]: OmniSharp.MSBuild.ProjectManager
        Failed to load project file '/home/thaun/Documents/Projects/orkel-pi/ProductionInsight/Api/Api.csproj'.
/home/thaun/Documents/Projects/orkel-pi/ProductionInsight/Api/Api.csproj
/usr/share/dotnet/sdk/5.0.104/Sdks/Microsoft.NET.Sdk.Razor/build/netstandard2.0/Microsoft.NET.Sdk.Razor.ScopedCss.targets(118,3): Error: The "Microsoft.AspNetCore.Razor.Tasks.DiscoverDefaultScopedCssItems" task could not be loaded from the assembly /usr/share/dotnet/sdk/5.0.104/Sdks/Microsoft.NET.Sdk.Razor/build/netstandard2.0/../../tasks/net46/Microsoft.NET.Sdk.Razor.Tasks.dll. Invalid Image Confirm that the <UsingTask> declaration is correct, that the assembly and all its dependencies are available, and that the task contains a public class that implements Microsoft.Build.Framework.ITask.

[fail]: OmniSharp.MSBuild.ProjectManager
        Attempted to update project that is not loaded: /home/thaun/Documents/Projects/orkel-pi/ProductionInsight/Api/Api.csproj```

[JoeRobich]

@ThomasAunvik Thanks for all the great resources that you’ve provided.

This issue is a packaging issue with Arch’s dotnet-sdk package where the net46 Razor build tasks are missing from the Razor SDK. This file /usr/share/dotnet/sdk/5.0.104/Sdks/Microsoft.NET.Sdk.Razor/tasks/net46/Microsoft.NET.Sdk.Razor.Tasks.dll is missing from the package file listing https://archlinux.pkgs.org/rolling/archlinux-community-x86_64/dotnet-sdk-5.0.5.sdk202-1-x86_64.pkg.tar.zst.html.

Your project builds fine using dotnet build because it looks for the net5 build tasks which are available. Because the C# extension relies on Mono to support .NET Full Framework projects, we look for the Full Framework net46 build tasks which are missing.

This comment provides a work around https://github.com/OmniSharp/omnisharp-vscode/issues/4360#issuecomment-801181468 or you can try installing the dotnet-sdk-bin package which appears to have the necessary file https://archlinux.pkgs.org/rolling/chaotic-aur-x86_64/dotnet-sdk-bin-5.0.3.sdk200-1-x86_64.pkg.tar.zst.html.

@NTaylorMullen just a fyi

[ThomasAunvik]

It would seem downloading the -bin version fixed the problem 👍 Closing this issue since #4360 already exists.