feat: implement closing related features.

src/Ursa/Controls/Dialog/DialogControl.cs

@@ -13,15 +13,36 @@ public class DialogControl: ContentControl
     
     
     private Button? _closeButton;
-    public event EventHandler OnClose;
+    public event EventHandler<object?> OnClose;
 
     protected override void OnApplyTemplate(TemplateAppliedEventArgs e)
     {
         base.OnApplyTemplate(e);
+        if (_closeButton != null)
+        {
+            _closeButton.Click -= Close;
+        }
+        _closeButton = e.NameScope.Find<Button>(PART_CloseButton);
+        if (_closeButton is not null)
+        {
+            _closeButton.Click += Close;
+        }
     }
 
     public void Show()
     {
         
     }
+
+    private void Close(object sender, object args)
+    {
+        if (this.DataContext is IDialogContext context)
+        {
+            OnClose?.Invoke(this, context.DefaultCloseResult);
+        }
+        else
+        {
+            OnClose?.Invoke(this, null);
+        }
+    }
 }