.NET Windows Forms in a Nutshell

Name

DragEventArgs

Synopsis

This class encapsulates the event arguments for the Control.DragEnter, Control.DragDrop, and Control.DragOver events.

When you start a drag-drop operation using Control.DoDragDrop(), you can specify the DragDropEffects that the drag source can support.

Then, as the drag-drop action proceeds, controls receive DragEnter, DragDrop, and DragOver events, which have DragEventArgs. You can retrieve the AllowedEffect property to determine what the source will permit, and then set the Effect property to specify which you can support as a target. It will also raise GiveFeedback events, which allow you to determine the current Effect, perhaps changing the Control object’s appearance or cursors. You might base this on the KeyState. Sadly, the KeyState has not been well encapsulated, and you have to mess around with magic numbers in a bitfield:

1

The left mouse button

2

The right mouse button

4

The Shift key

8

The Control key

16

The middle mouse button

32

The Alt key

You can also retrieve the actual Data that is being dragged, through the IDataObject that encapsulates it.

public class DragEventArgs : EventArgs {

// Public Constructors

   public DragEventArgs(IDataObject data, int keyState, int x, int y, DragDropEffects allowedEffect, 

        DragDropEffects effect);

// Public Instance Properties

   public DragDropEffects AllowedEffect{get; }

   public IDataObject Data{get; }

   public DragDropEffects Effect{set; get; }

   public int KeyState{get; }

   public int X{get; }

   public int Y{get; }

}

Hierarchy

System.Object ...