dotnet watch Fails in Blazor

[j4587698]

Describe the bug

dotnet watch command fails when a Blazor project references any multi-target framework project

To Reproduce

BlazorApp1.zip
dotnet watch run this project and change any razor file.

Exceptions (if any)

dotnet watch ⌚ File added: .\Components\Pages\Home.razor~
dotnet watch ⌚ File changed: .\Components\Pages\Home.razor
dotnet watch ⏳ Waiting for a file to change before restarting dotnet...
dotnet watch ❌ System.ArgumentException: An item with the same key has already been added. Key: D:\dotnet\BlazorApp1\ClassLibrary1\ClassLibrary1.csproj
at System.Collections.Generic.Dictionary2.TryInsert(TKey key, TValue value, InsertionBehavior behavior) at System.Collections.Generic.Dictionary2.Add(TKey key, TValue value)
at System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement](IEnumerable1 source, Func2 keySelector, Func2 elementSelector, IEqualityComparer1 comparer)
at System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement](IEnumerable1 source, Func2 keySelector, Func`2 elementSelector)
at Microsoft.DotNet.Watcher.Tools.IncrementalMSBuildWorkspace.UpdateProjectConeAsync(String rootProjectPath, CancellationToken cancellationToken)
at Microsoft.DotNet.Watcher.HotReloadDotNetWatcher.WatchAsync(CancellationToken shutdownCancellationToken)
at Microsoft.DotNet.Watcher.HotReloadDotNetWatcher.WatchAsync(CancellationToken shutdownCancellationToken)
at Microsoft.DotNet.Watcher.HotReloadDotNetWatcher.WatchAsync(CancellationToken shutdownCancellationToken)
at Microsoft.DotNet.Watcher.HotReloadDotNetWatcher.WatchAsync(CancellationToken shutdownCancellationToken)
at Microsoft.DotNet.Watcher.HotReloadDotNetWatcher.WatchAsync(CancellationToken shutdownCancellationToken)
at Microsoft.DotNet.Watcher.Program.RunAsync()

Further technical details

dotnet --info
.NET SDK:
Version: 9.0.100-rc.2.24474.11
Commit: 315e130
Workload version: 9.0.100-manifests.cea95dba
MSBuild version: 17.12.0-preview-24473-03+fea15fbd1

Runtime Environment:
OS Name: Windows
OS Version: 10.0.22631
OS Platform: Windows
RID: win-x64
Base Path: C:\Program Files\dotnet\sdk\9.0.100-rc.2.24474.11\

.NET workloads installed:
Configured to use loose manifests when installing new manifests.
There are no installed workloads to display.

Host:
Version: 9.0.0-rc.2.24473.5
Architecture: x64
Commit: 990ebf52fc

.NET SDKs installed:
6.0.101 [C:\Program Files\dotnet\sdk]
6.0.402 [C:\Program Files\dotnet\sdk]
7.0.100 [C:\Program Files\dotnet\sdk]
8.0.100 [C:\Program Files\dotnet\sdk]
9.0.100-rc.2.24474.11 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 6.0.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 6.0.10 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 7.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 8.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 9.0.0-rc.2.24474.3 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 6.0.1 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.10 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 7.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 9.0.0-rc.2.24473.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 6.0.1 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.10 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 7.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 8.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 9.0.0-rc.2.24474.4 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
None

Environment variables:
Not set

global.json file:
Not found

Learn more:
https://aka.ms/dotnet/info

Download .NET:
https://aka.ms/dotnet/download

Any IDE