dotnet watch on net6.0 project results in FileNotFoundException for SystemRuntime

Description

When running the dotnet watch from .net 7 on a net6.0 project, a FileNotFoundException is thrown claiming that System.Runtime, Version=7.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a could not be found. net7.0 and net5.0 projects work fine.

Reproduction Steps

dotnet new console -f net6.0
dotnet watch run

Expected behavior

The program should output Hello, World!.

Actual behavior

dotnet watch 🔥 Hot reload enabled. For a list of supported edits, see https://aka.ms/dotnet/hot-reload.
  💡 Press "Ctrl + R" to restart.
dotnet watch 🔧 Building...
  Determining projects to restore...
  All projects are up-to-date for restore.
  watchtest -> D:\Test\watchtest\bin\Debug\net6.0\watchtest.dll
dotnet watch 🚀 Started
Unhandled exception. System.IO.FileNotFoundException: Could not load file or assembly 'System.Runtime, Version=7.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. The system cannot find the file specified.
File name: 'System.Runtime, Version=7.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'
   at System.Reflection.RuntimeAssembly.GetType(QCallAssembly assembly, String name, Boolean throwOnError, Boolean ignoreCase, ObjectHandleOnStack type, ObjectHandleOnStack keepAlive, ObjectHandleOnStack assemblyLoadContext)
   at System.Reflection.RuntimeAssembly.GetType(String name, Boolean throwOnError, Boolean ignoreCase)
   at System.Reflection.Assembly.GetType(String name, Boolean throwOnError)
   at System.StartupHookProvider.CallStartupHook(StartupHookNameOrPath startupHook)
   at System.StartupHookProvider.ProcessStartupHooks()
dotnet watch ❌ Exited with error code -532462766
dotnet watch ⏳ Waiting for a file to change before restarting dotnet...

Regression?

This is a regression from SDK 7.0.100-rc.2

Known Workarounds

This can be worked around by creating a global.json file and pointing it to the v6 SDK (thanks @nicholashead)

{
    "sdk": {
        "version": "6.0.403"
    }
}

Alternatively, adding any argument after dotnet watch run will work. e.g.

dotnet watch run bogus

(thanks @akorchev)

Configuration

.NET SDK: Version: 7.0.100 Commit: e12b7af219

Runtime Environment: OS Name: Windows OS Version: 10.0.19044 OS Platform: Windows RID: win10-x64 Base Path: C:\Program Files\dotnet\sdk\7.0.100\

Host: Version: 7.0.0 Architecture: x64 Commit: d099f075e4

Other information

It’s possible that my installation is corrupted. However I have uninstalled and reinstalled several times

[akorchev]

I’ve hit this too and discovered this issue. Strangely enough putting anything after “run” seems to fix the problem (even without global.json) e.g. dotnet watch run bogus. Found it by dumb luck after a typo.

[nicholashead]

Would be interested to know if anyone got this recently after updating Visual Studio 2022/.NET Core 7.

Yes, this is exactly when it started happening for me. I was not running any betas or anything.