The Control.DragOver event is raised when the mouse cursor moves within the bounds of the control during a drag-and-drop operation.
The following describes how and when events related to drag-and-drop operations are raised.
The Control.DoDragDrop(object, DragDropEffects) method determines the control under the current cursor location. It then checks to see if the control is a valid drop target.
If the control is a valid drop target, the Control.GiveFeedback event is raised with the drag-and-drop effect specified. For a list of drag-and-drop effects, see the System.Windows.Forms.DragDropEffects enumeration.
Changes in the mouse cursor position, keyboard state, and mouse button state are tracked.
If the user moves out of a window, the Control.DragLeave event is raised.
If the mouse enters another control, the Control.DragEnter for that control is raised.
If the mouse moves but stays within the same control, the Control.DragOver event is raised.
If there is a change in the keyboard or mouse button state, the Control.QueryContinueDrag event is raised and determines whether to continue the drag, to drop the data, or to cancel the operation based on the value of the QueryContinueDragEventArgs.Action property of the event's System.Windows.Forms.QueryContinueDragEventArgs.
If the value of System.Windows.Forms.DragAction value is Continue, the Control.DragOver event is raised to continue the operation and the Control.GiveFeedback event is raised with the new effect so appropriate visual feedback can be set. For a list of valid drop effects, see the System.Windows.Forms.DragDropEffects enumeration.
If the value of System.Windows.Forms.DragAction is Drop, the drop effect value is returned to the source, so the source application can perform the appropriate operation on the source data; for example, cut the data if the operation was a move.
For more information about handling events, see Consuming Events.