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You use Microsoft .NET Framework 4 to create a Windows Forms application.  
The application includes a RichTextBox control and a ListBox control. The ListBox control is populated with a list of valid file names.  
The application allows users to drag a ListBox item to the RichTextBox control. 
You need to provide a visual indication that a file that is dragged can be dropped on the RichTextBox control. 
What should you do?（）

You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application.  
The application uses the drag-and-drop functionality. 
You need to ensure that the drag-and-drop operation is stopped when a user moves the cursor outside the boundaries of the application form. 
Which enumeration member should you use?（）