單項選擇題

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?（）

A. Use a DoubleAnimation class.
B. Use a Storyboard animation class.
C. Use the DragDropEffects enumeration.
D. Use the DragAction enumeration.

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單項選擇題

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?（）

A. DragAction.Cancel
B. DragAction.Drop
C. DragDropEffects.None
D. DragDropEffects.All

多項選擇題

You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application.
The application uses the background worker process (BWP).
When the user clicks a button,
the background worker executes a method named DoCalculations asynchronously.
You need to implement a progress bar on the user interface (UI) that informs the user of the progress of DoCalculations.
Which two actions should you perform?（）

A. Modify the Value property of the progress bar in DoCalculations.
B. Modify the Value property of the progress bar in the ProgressChanged event handler of the background worker.
C. Modify the Value property of the progress bar in the RunWorkerCompleted event handler of the background worker.
D. Call the ReportProgress method of the background worker in DoCalculations.
E. Call the ReportProgress method of the background worker in the DoWork event handler of the background worker.