From 5e0db94a8129044e8a6e46f2aeaf0305f5a13b6b Mon Sep 17 00:00:00 2001
From: "Simon Zhao (BEYONDSOFT CONSULTING INC)" <v-weidzh@microsoft.com>
Date: Fri, 29 May 2026 15:02:38 +0800
Subject: [PATCH] Fix ComboBox dark mode theme on first TabPage

---
 .../Forms/Controls/TabControl/TabControl.cs      | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/System.Windows.Forms/System/Windows/Forms/Controls/TabControl/TabControl.cs b/src/System.Windows.Forms/System/Windows/Forms/Controls/TabControl/TabControl.cs
index 73f78d1df17..9c063187ad4 100644
--- a/src/System.Windows.Forms/System/Windows/Forms/Controls/TabControl/TabControl.cs
+++ b/src/System.Windows.Forms/System/Windows/Forms/Controls/TabControl/TabControl.cs
@@ -1787,9 +1787,19 @@ 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.