SimonZhao888

Following controls are missing test coverage for public methods: **System.Windows.Forms** - [ ] Button https://github.com/dotnet/winforms/pull/10693 - [ ] CheckBox https://github.com/dotnet/winforms/pull/10693, https://github.com/dotnet/winforms/pull/11249 - [ ] FlatButton https://github.com/dotnet/winforms/pull/10693 - [ ] RadioButton...

> 1. generate public API surface for NETFX 481 System.Windows.Forms.dd and for NET9 SystemWindows.Froms.dll and find public or protected APIs that we had removed 1. System.Windows.Forms.StatusBar override System.Windows.Forms.StatusBar.BackColor.get -> System.Drawing.Color...

When we use reverse lookup, TreeWalker can obtain the TabItem controls.   [WinFormsApp71.zip](https://github.com/dotnet/winforms/files/13655700/WinFormsApp71.zip) @leind375, hope this can help you to solve your problem.

> The workaround above (using GetLastChild() and GetPreviousSibling() also has a defect - GetPreviousSibling is also returning children, not just siblings. We need to modify the code appropriately, e.g. try...

Hi @Tanya-Solyanik, because we had closed [issue 8326](https://github.com/dotnet/winforms/issues/8326), which is related to  so we want to know if this issue needs to be fixed or not.

Hi @Tanya-Solyanik , Which way should we choose to fix this issue? Revert the related changes or delete the public method which only used to throw PlatformNotSupportedException?

LGTM!