Fluent Theme CornerRadius

[robert-abeo]

In the new, unreleased Fluent theme based on WPF UI, what is the correct way to set the corner radius? These are set in the styles using a Border.CornerRadius attached property. That works well enough in the ControlTemplate, but what about when I want to set this in a view?

For example if I have a TextBox as below and try to set it, it will fail.

<TextBox Border.CornerRadius="0,4,4,0" />

I can set this through a style but it's really cumbersome to do so. ModernWPF added a separate attached property for this case ControlHelper.CornerRadius. I think we might need something similar in WPF... however, we should just add CornerRadius to the controls directly now. That change isn't monumental and was done in Avalonia UI in a fairly straightforward way:

AvaloniaUI/Avalonia#6347

[lindexi]

Keeping this be open until the Win11 Theme Stylus finish. And I'm worried this feature is still missing.