Fix CheckBox/RadioButton Appearance switching in Dark Mode

[LeafShi1]

Fixes #14191

Root Cause

When switching the Appearance property between Normal and Button via PropertyGrid in Dark Mode, the CheckBox/RadioButton controls failed to update their visual state correctly.

The issue occurred because:

1. In Dark Mode, the OwnerDraw property returns different values based on the Appearance setting
2. When Appearance = Button with FlatStyle.Standard in Dark Mode, OwnerDraw becomes false (system-drawn)
3. When Appearance = Normal, OwnerDraw is always true (custom-drawn)
4. The Appearance setter was not calling UpdateOwnerDraw() to handle this state transition
5. Without calling UpdateOwnerDraw(), the control styles (ControlStyles.UserPaint, ControlStyles.UserMouse) were not updated, and the window handle was not recreated

Proposed changes

• Added UpdateOwnerDraw() call in the Appearance setter for both CheckBox and RadioButton
• Optimized call order to avoid unnecessary operations:
  Handle state change first (may RecreateHandle) and then refresh if handle wasn't recreated

Customer Impact

• CheckBox and RadioButton now correctly switch between Normal and Button appearance in Dark Mode

Regression?

• Yes

Risk

• Minimal

Screenshots

Before

The CheckBox/RadioButton cannot back to normal status when switching the Appearance property in propertyGrid

BeforeChanges.mp4

After

CheckBox / RadioButton correctly switch between Normal and Button appearance in Dark Mode

AfterChanges.mp4

Test methodology

• Manually

Test environment(s)

• .net 11.0.0-alpha.1.26055.114

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull request overview

This PR fixes a visual update bug in CheckBox and RadioButton controls when switching between Normal and Button appearance in Dark Mode. The root cause was that UpdateOwnerDraw() was called too late (only in the else branch), preventing proper control style synchronization and handle recreation when needed.

Key Changes:

• Moved UpdateOwnerDraw() call to execute before the if/else branching logic in both CheckBox and RadioButton
• Removed the previous UpdateOwnerDraw() call from the else branch
• Updated inline comments to accurately reflect the new execution order and behavior

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/System.Windows.Forms/System/Windows/Forms/Controls/Buttons/CheckBox.cs	Repositioned UpdateOwnerDraw() call to occur before if/else logic, ensuring OwnerDraw state is updated before branching decisions are made
src/System.Windows.Forms/System/Windows/Forms/Controls/Buttons/RadioButton.cs	Applied identical fix as CheckBox - moved UpdateOwnerDraw() before if/else logic for proper Dark Mode appearance switching

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.15319%. Comparing base (15506ad) to head (a4d7b5b).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #14194         +/-   ##
===================================================
+ Coverage   77.15242%   77.15319%   +0.00076%     
===================================================
  Files           3279        3279                 
  Lines         645333      645333                 
  Branches       47720       47720                 
===================================================
+ Hits          497890      497895          +5     
+ Misses        143757      143741         -16     
- Partials        3686        3697         +11     

Flag	Coverage Δ
Debug	77.15319% <100.00000%> (+0.00076%)	⬆️
integration	18.98737% <0.00000%> (+0.00312%)	⬆️
production	52.01720% <100.00000%> (+0.00174%)	⬆️
test	97.40559% <ø> (ø)
unit	49.46431% <100.00000%> (+0.02256%)	⬆️

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[KlausLoeffelmann]

Perfect, we were on the right track here! :-)

Thanks for fixing this!

[LeafShi1]

/backport to release/10.0

[github-actions]

Started backporting to release/10.0 (link to workflow run)