我们用WPF用的Popup时候会发现，当 StaysOpen=True 的时候，因为Popup不会消失，在父窗口移走的时候Popup仍旧在原地。。。作者在国外网站上无意间发现了这个解决方案，拿出来给大家分享：

方法是为Popup定义一个附加属性。代码如下。

1     public class PopopHelper 2     { 3         public static DependencyObject GetPopupPlacementTarget(DependencyObject obj) 4         { 5             return (DependencyObject)obj.GetValue(PopupPlacementTargetProperty); 6         } 7  8         public static void SetPopupPlacementTarget(DependencyObject obj, DependencyObject value) 9         {10             obj.SetValue(PopupPlacementTargetProperty, value);11         }12 13         // Using a DependencyProperty as the backing store for PopupPlacementTarget.  This enables animation, styling, binding, etc...14         public static readonly DependencyProperty PopupPlacementTargetProperty =15             DependencyProperty.RegisterAttached("PopupPlacementTarget", typeof(DependencyObject), typeof(PopopHelper), new PropertyMetadata(null,OnPopupPlacementTargetChanged));16 17         private static void OnPopupPlacementTargetChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)18         {19             if (e.NewValue != null)20             {21                 DependencyObject popupPopupPlacementTarget = e.NewValue as DependencyObject;22                 Popup pop = d as Popup;23 24                 Window w = Window.GetWindow(popupPopupPlacementTarget);25                 if (null != w)26                 {27                     w.LocationChanged += delegate28                     {29                         var offset = pop.HorizontalOffset;30                         pop.HorizontalOffset = offset + 1;31                         pop.HorizontalOffset = offset;32                     };33                 }34             }35         }36         37     }

之后只需要在Popup控件上这样写即可：

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本文的示例工程可以从下载。

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