`ArgumentException` with `WriteableBitmap.WritePixels`

[loicmorvan]

• .NET Core Version: 6.0
• Windows version: Windows 11 (21H2)
• Does the bug reproduce also in WPF for .NET Framework 4.8?: I don't know
• Is this bug related specifically to tooling in Visual Studio (e.g. XAML Designer, Code editing, etc...)? No.

Problem description:

Calling WriteableBitmap.WritePixels just crashes with an ArgumentException without paramName.

Reproduced in this repos: https://github.com/loicmorvan/BugWriteableBitmap

Actual behavior:

Crashes with an ArgumentException without paramName.

Expected behavior:

No crash, and pixels updated into the bitmap.

Minimal repro:

https://github.com/loicmorvan/BugWriteableBitmap

[lindexi]

Hi @loicmorvan It looks like your code bug and not the wpf issues.

You should input the right sourceBufferStride argument to WritePixels:

writeableBitmap.WritePixels(rect, pixels, sourceBufferStride: 4 * width, 0, 0);

And I found your PixelFormats is not Bgra32, and is it right?

[loicmorvan]

OK, thanks!
Putting 4 * width did work.

But still there is mistery in there: why should I put the length of one line in bytes?
Should we consider improving the API and its documentation to make it clearer?

[dipeshmsft]

Hey @loicmorvan , I looked into this issue and updated the comments in the code for better understanding. Will close the issue once the PR gets reviewed and merged.