private void OnSelectionChangedAction(List <_Control> selectedList)
 {
     if (selectedList.Count == 0)
     {
         PropertyGrid.Browse(DesginControl, null);
         MessageTextBlock.Text = "可以选择需要添加的元素,或者鼠标选取屏幕上元素删除、移动等操作";
     }
     else if (selectedList.Count == 1)
     {
         PropertyGrid.Browse(selectedList[0], selectedList[0].GetProperties());
         MessageTextBlock.Text = string.Format("选择了一个{0}对象", selectedList[0].ToString());
     }
     else
     {
         PropertyGrid.Browse(null, null);
         MessageTextBlock.Text = string.Format("选择了{0}个对象", selectedList.Count);
     }
 }