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Fix ComboBox dark mode theme on first TabPage #14128

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Fix ComboBox dark mode theme on first TabPage #14128

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82669f4
Initial plan
Copilot Dec 10, 2025
89eb45b
Fix: ComboBox dark mode on first TabPage - only style direct children
Copilot Dec 10, 2025
1f75489
Address code review: return SetWindowTheme result
Copilot Dec 10, 2025
cd50a93
Fixes TabControl tab title background color regression compared to .N…
Dec 10, 2025
c0b6d94
Revert the latest change
Dec 11, 2025
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16 changes: 13 additions & 3 deletions src/System.Windows.Forms/System/Windows/Forms/Controls/TabControl/TabControl.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1790,9 +1790,19 @@ private bool ShouldSerializeItemSize()
return !_padding.Equals(s_defaultPaddingPoint);
}

private BOOL StyleChildren(HWND handle) =>
PInvoke.SetWindowTheme(handle, $"{DarkModeIdentifier}_{ExplorerThemeIdentifier}", null)
.Succeeded;
private BOOL StyleChildren(HWND handle)
{
// Only apply theme to direct children (TabPages), not to controls within TabPages.
// Controls like ComboBox need their own specific dark mode themes.
HWND parent = PInvoke.GetParent(handle);
if (parent == HWND)
{
return PInvoke.SetWindowTheme(handle, $"{DarkModeIdentifier}_{ExplorerThemeIdentifier}", null)
.Succeeded;
}

return true;
}

/// <summary>
/// Returns a string representation for this control.
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