Fix issue 14025: [DarkMode] the item lost dot line when using the mouse to expand the dropdown panel for SelectionPanelRadioButton

src/System.Windows.Forms.Design/src/System/Drawing/SelectionPanelBase.SelectionPanelRadioButton.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Windows.Forms;
+using System.Windows.Forms.VisualStyles;
 
 namespace System.Drawing.Design;
 
@@ -16,6 +17,45 @@ public SelectionPanelRadioButton()
 
         protected override bool ShowFocusCues => true;
 
+        protected override void WndProc(ref Message m)
+        {
+            base.WndProc(ref m);
+
+            if (m.MsgInternal != PInvokeCore.WM_PAINT || !Focused || !Application.IsDarkModeEnabled)
+            {
+                return;
+            }
+
+            using Graphics g = CreateGraphics();
+            Rectangle focusBounds = GetFocusBounds(g);
+            if (focusBounds.Width <= 0 || focusBounds.Height <= 0)
+            {
+                return;
+            }
+
+            ControlPaint.DrawFocusRectangle(g, focusBounds, ForeColor, BackColor);
+        }
+
+        private Rectangle GetFocusBounds(Graphics graphics)
+        {
+            if (Application.RenderWithVisualStyles && VisualStyleRenderer.IsSupported)
+            {
+                VisualStyleElement element = Checked
+                    ? VisualStyleElement.Button.PushButton.Pressed
+                    : VisualStyleElement.Button.PushButton.Normal;
+
+                if (VisualStyleRenderer.IsElementDefined(element))
+                {
+                    VisualStyleRenderer renderer = new(element);
+                    return renderer.GetBackgroundContentRectangle(graphics, ClientRectangle);
+                }
+            }
+
+            Rectangle focusBounds = ClientRectangle;
+            focusBounds.Inflate(-SystemInformation.Border3DSize.Width, -SystemInformation.Border3DSize.Height);
+            return focusBounds;
+        }
+
         protected override bool IsInputKey(Keys keyData) => keyData switch
         {
             Keys.Left or Keys.Right or Keys.Up or Keys.Down or Keys.Return => true,