This is related to this issue, around a breaking change somewhere after .NET 8.0.206 that is impacted (as far as I can tell) from the following convergence:

1. You are using the Microsoft.NET.Sdk.Web SDK.
2. You are using an SDK later than 8.0.206 (I've used up to 401 and can reliably reproduce this).
3. You are using the Paket tool as your .NET package management client.

If all of these things are true and you dotnet watch build or run from the folder of the project, things go wrong. I suspect it's something that's changed since 8.0.206 (or the Sdk.Web) that has somehow broken Paket.

We have seen this with multiple customers of SAFE Stack, which uses Paket and ASP .NET Core - when people upgraded to 8.0.3xx, things started going wrong with no code changes at all.

This repository contains a working reproduction of the issue.

Here are some steps to reproduce:

1. Install a version of .NET 8.0 after 8.0.206 (I'm using 8.0.401).
2. Make a clean folder and cd to it.
3. dotnet new globaljson
4. Set it to e.g.

{
    "sdk": {
        "version": "8.0.401"
    }
}

1. dotnet new console -lang F#
2. dotnet tool install paket --create-manifest-if-needed
3. dotnet paket add FSharp.Core

Now, observe the following behaviours:

dotnet watch build ❌

dotnet watch � Started
  Determining projects to restore...
  Unhandled exception. System.IO.FileNotFoundException: Could not load file or assembly 'System.Runtime, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. The system cannot find the file specified.
  File name: 'System.Runtime, Version=6.0.0.0, 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()


D:\code\runthru\.paket\Paket.Restore.targets(171,3): error MSB3073: The command "dotnet paket restore" exited with code -532462766. [D:\code\runthru\runthru.fsproj]

Build FAILED.

dotnet watch run ❌

error MSB3073: The command "dotnet paket restore" exited with code -532462766

Workarounds

• Don't use watch; dotnet build and dotnet run on their own work. ✅
• Change global.json to pin to 8.0.206. ✅
• Change the fsproj SDK to Microsoft.NET.Sdk ✅
• Add --no-restore to either watch or build. ✅