ArgumentException: 指定的 Visual 已经是另一个 Visual 的子级或者已经是 CompositionTarget 的根。
--Message: 指定的 Visual 已经是另一个 Visual 的子级或者已经是 CompositionTarget 的根。
StackTrace:
   在 System.Windows.Media.VisualCollection.Insert(Int32 index, Visual visual)
   在 System.Windows.Controls.UIElementCollection.InsertInternal(Int32 index, UIElement element)
   在 DynamicClass.CustomWindowLogic.Panel_Drop(Object sender, DragEventArgs e)
   在 System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
   在 System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
   在 System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   在 System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
   在 System.Windows.OleDropTarget.RaiseDragEvent(RoutedEvent dragEvent, Int32 dragDropKeyStates, Int32& effects, DependencyObject target, Point targetPoint)
   在 System.Windows.OleDropTarget.MS.Win32.UnsafeNativeMethods.IOleDropTarget.OleDrop(Object data, Int32 dragDropKeyStates, Int64 point, Int32& effects)
   在 MS.Win32.UnsafeNativeMethods.DoDragDrop(IDataObject dataObject, IOleDropSource dropSource, Int32 allowedEffects, Int32[] finalEffect)
   在 System.Windows.OleServicesContext.OleDoDragDrop(IDataObject dataObject, IOleDropSource dropSource, Int32 allowedEffects, Int32[] finalEffect)
   在 System.Windows.DragDrop.OleDoDragDrop(DependencyObject dragSource, DataObject dataObject, DragDropEffects allowedEffects)
   在 System.Windows.DragDrop.DoDragDrop(DependencyObject dragSource, Object data, DragDropEffects allowedEffects)
   在 DynamicClass.CustomWindowLogic.<>c__DisplayClass23.<CreateAppButton>b__21(Object s, MouseEventArgs e)
   在 System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
   在 System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
   在 System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   在 System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
   在 System.Windows.UIElement.RaiseTrustedEvent(RoutedEventArgs args)
   在 System.Windows.Input.InputManager.ProcessStagingArea()
   在 System.Windows.Input.InputManager.ProcessInput(InputEventArgs input)
   在 System.Windows.Input.InputProviderSite.ReportInput(InputReport inputReport)
   在 System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel)
   在 System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   在 System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   在 MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   在 MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
   在 System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   在 System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)