ComboBox border not visible in strip controls when navigated via keyboard

[Syareel-Sukeri]

.NET version

.NET 10.0.100-alpha.1.25058.38

Did it work in .NET Framework?

Yes

Did it work in any of the earlier releases of .NET Core or .NET 5+?

This issue cannot be reproduced in .NET 8.

Issue description

When a ComboBox is added to any strip control (MenuStrip, ToolStrip, StatusStrip, ContextMenuStrip), its border becomes invisible when focused using the Tab or Arrow keys.

Current behavior (.NET 9.0 and .NET 10.0)
The ComboBox receives focus, but its border is not visible when navigated via keyboard.

Border10.mp4

Expected behavior (.NET 8)
ComboBox should display a visible border when focused, even when navigated via keyboard.

Border8.mp4

Steps to reproduce

1. Create WinForms .NET Core app with MenuStrip.
2. Add a ComboBox directly to the MenuStrip or use it as a dropdown item.
3. Run the project
4. Use the Tab or Down Arrow key to navigate to the ComboBox.

[Tanya-Solyanik]

Please investigate the root cause and update this bug with it.