Fix.

Author: KlausLoeffelmann

src/System.Windows.Forms/System/Windows/Forms/Controls/ToolStrips/ToolStripSystemDarkModeRenderer.cs

@@ -258,7 +258,7 @@ protected override void OnRenderItemBackground(ToolStripItemRenderEventArgs e)
         if (e.Item.Selected || e.Item.Pressed)
         {
             // Dark mode selection highlight
-            using Brush highlightBrush = GetDarkModeBrush(SystemColors.Highlight);
+            using var highlightBrush = GetDarkModeBrush(SystemColors.Highlight);
             e.Graphics.FillRectangle(highlightBrush, bounds);
         }
         else
@@ -307,7 +307,7 @@ protected override void OnRenderButtonBackground(ToolStripItemRenderEventArgs e)
 
         if (isPressed || isSelected)
         {
-            Brush fillColor = isPressed
+            var fillColor = isPressed
                 ? GetDarkModeBrush(SystemColors.ControlDark)
                 : GetDarkModeBrush(SystemColors.Highlight);
 
@@ -343,7 +343,7 @@ protected override void OnRenderSplitButtonBackground(ToolStripItemRenderEventAr
         // Render the background based on state
         if (splitButton.Selected || splitButton.Pressed)
         {
-            Brush fillColor = splitButton.Pressed
+            var fillColor = splitButton.Pressed
                 ? GetDarkModeBrush(SystemColors.ControlDark)
                 : GetDarkModeBrush(SystemColors.Highlight);
 
@@ -352,7 +352,7 @@ protected override void OnRenderSplitButtonBackground(ToolStripItemRenderEventAr
 
         // Draw the split line
         Rectangle dropDownRect = splitButton.DropDownButtonBounds;
-        using Pen linePen = GetDarkModePen(SystemColors.ControlDark);
+        using var linePen = GetDarkModePen(SystemColors.ControlDark);
 
         e.Graphics.DrawLine(
             linePen,