Invoking UpdateOwnerDraw in BackgroundImage property to update the OwnerDraw flag to ensure correct visual behavior

Author: Leaf Shi

src/System.Windows.Forms/PublicAPI.Unshipped.txt

@@ -1,3 +1,4 @@
+override System.Windows.Forms.Button.BackgroundImage.set -> void
 static System.Windows.Forms.Application.SetColorMode(System.Windows.Forms.SystemColorMode systemColorMode) -> void
 static System.Windows.Forms.TaskDialog.ShowDialogAsync(nint hwndOwner, System.Windows.Forms.TaskDialogPage! page, System.Windows.Forms.TaskDialogStartupLocation startupLocation = System.Windows.Forms.TaskDialogStartupLocation.CenterOwner) -> System.Threading.Tasks.Task<System.Windows.Forms.TaskDialogButton!>!
 static System.Windows.Forms.TaskDialog.ShowDialogAsync(System.Windows.Forms.IWin32Window! owner, System.Windows.Forms.TaskDialogPage! page, System.Windows.Forms.TaskDialogStartupLocation startupLocation = System.Windows.Forms.TaskDialogStartupLocation.CenterOwner) -> System.Threading.Tasks.Task<System.Windows.Forms.TaskDialogButton!>!

src/System.Windows.Forms/System/Windows/Forms/Controls/Buttons/Button.cs

@@ -148,6 +148,18 @@ public virtual DialogResult DialogResult
         }
     }
 
+    public override Image? BackgroundImage
+    {
+        set
+        {
+            base.BackgroundImage = value;
+
+            // BackgroundImage changes may affect rendering logic,
+            // so we manually update the OwnerDraw flag to ensure correct visual behavior.
+            UpdateOwnerDraw();
+        }
+    }
+
     /// <summary>
     ///  Defines, whether the control is owner-drawn. Based on this,
     ///  the UserPaint flags get set, which in turn makes it later
@@ -166,8 +178,6 @@ private protected override bool OwnerDraw
                 && Image is null
                 // ...or a BackgroundImage, except if...
                 && BackgroundImage is null
-                // Delay BackgroundImage check until handle is created to avoid early null misjudgment
-                && IsHandleCreated
                 // ...the user wants to opt out of implicit DarkMode rendering.
                 && DarkModeRequestState is true