# System.Windows.Forms.Design

``` diff
 namespace System.Windows.Forms.Design {
     [ToolboxItemAttribute(false)]
     public class ComponentEditorForm : Form {
         [BrowsableAttribute(false)]
         [EditorBrowsableAttribute(1)]
-        public new event EventHandler AutoSizeChanged;
+        public new event EventHandler? AutoSizeChanged;
-        protected virtual void OnSelChangeSelector(object source, TreeViewEventArgs e);
+        protected virtual void OnSelChangeSelector(object? source, TreeViewEventArgs e);
-        public virtual DialogResult ShowForm(IWin32Window owner);
+        public virtual DialogResult ShowForm(IWin32Window? owner);
-        public virtual DialogResult ShowForm(IWin32Window owner, int page);
+        public virtual DialogResult ShowForm(IWin32Window? owner, int page);
     }
 }
```

