# System.Drawing.Design

``` diff
 namespace System.Drawing.Design {
     public interface IPropertyValueUIService {
-        event EventHandler PropertyUIValueItemsChanged;
+        event EventHandler? PropertyUIValueItemsChanged;
     }
     public class PropertyValueUIItem {
-        public PropertyValueUIItem(Image uiItemImage, PropertyValueUIItemInvokeHandler handler, string tooltip);
+        public PropertyValueUIItem(Image uiItemImage, PropertyValueUIItemInvokeHandler handler, string? tooltip);
-        public virtual string ToolTip { get; }
+        public virtual string? ToolTip { get; }
     }
 }
```

