WriteableBitmap hangs when source bitmap is rendered on other thread

• .NET Core Version: 5.0.201
• Windows version: Windows 10x64 20H2 19042.906
• Does the bug reproduce also in WPF for .NET Framework 4.8? I’m not able to test: .NET Framework 4.8 not available in VS 2019 New Project wizard However, I can reproduce in .NET Framework 4.72.
• Is this bug related specifically to tooling in Visual Studio (e.g. XAML Designer, Code editing, etc…)? No.

Problem description:

WriteableBitmap isn’t thread safe.

Creating a WriteableBitmap from a bitmap that’s assigned to an Image control will hang the UI thread when the UI thread is busy rendering the image.

Actual behavior:

The WPF application will hang unexpectedly and randomly.

Expected behavior:

The WPF application should not hang.

Minimal repro:

https://github.com/SetTrend/BitmapSourceTest

private void ProcessImageAsync(string filePath)
{
  TransformedBitmap tb = new TransformedBitmap(new BitmapImage(new Uri(filePath)), new RotateTransform(90));

  CopyBitmapSourceToUi(tb);

  _ = new WriteableBitmap(tb);
}

private void CopyBitmapSourceToUi(BitmapSource image)
{
  BitmapSource uiSource;

  uiSource = BitmapFrame.Create(image);
  uiSource.Freeze();  // locks the bitmap source, so other threads can access

  Dispatcher.Invoke(() => origImage.Source = uiSource);
  //Thread.Sleep(10);   // WPF needs time to render the bitmap. During this period, creating a WriteableBitmap makes the program hang.
}

[SetTrend]

Thank you for your great efforts, @lindexi!

And will it run with my piece of code, and with BitmapSource.Create(), too?

[SetTrend]

@lindexi:

Splendid! It runs like a charm!

Good work!