microsoft / microsoft/CsWinRT

Bug: Passing Microsoft.Graphics.Canvas.UI.Xaml.CanvasControl.Invalidate as the callback argument to a DispatcherQueue.TryEnqueue causes an InvalidCastException in the WinRT runtime

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Dominant language
C#
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Description

Description

When trying to directly pass the Invalidate method of a Microsoft.Graphics.Canvas.UI.Xaml.CanvasControl instance as the callback argument of the TryEnqueue method of a DispatcherQueue instance an InvalidCastException is thrown.
When passing a lambda expression that just calls the Invalidate method, the exception is not thrown!

Steps To Reproduce

The following should do the trick (I have not verified this outside of my repo):

DispatcherQueue.TryEnqueue(GraphCanvas.Invalidate);

where GraphCanvas is a Microsoft.Graphics.Canvas.UI.Xaml.CanvasControl instance.
The following code does not throw the exception:

DispatcherQueue.TryEnqueue(() => GraphCanvas.Invalidate());
Expected Behavior

No InvalidCastException is thrown

Version Info

.NET 9.0 Framework

Additional Context

The following image shows one such exception with a stack trace:

Image

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the minimal C# reproduction using Microsoft.Graphics.Canvas.UI.Xaml.CanvasControl.Invalidate as the DispatcherQueue.TryEnqueue callback, and compare it with the lambda form. Trace the WinRT callback projection and InvalidCastException path; done means the direct method-group call no longer throws while the lambda behavior remains intact.

Written by the indexing model from the issue text.

Assessment

Tech stack
csharp
Domain
desktop
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
42/100

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