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Control.DragLeave Event

  • Reference

Definition

Namespace:
System.Windows.Forms
Assembly:
System.Windows.Forms.dll

Occurs when an object is dragged out of the control's bounds.

public:
 event EventHandler ^ DragLeave;
public event EventHandler DragLeave;
public event EventHandler? DragLeave;
member this.DragLeave : EventHandler 
Public Custom Event DragLeave As EventHandler

Event Type

EventHandler

Examples

The following code example demonstrates a drag-and-drop operation between two ListBox controls. The example calls the DoDragDrop method when the drag action starts. The drag action starts if the mouse has moved more than SystemInformation.DragSize from the mouse location during the MouseDown event. The IndexFromPoint method is used to determine the index of the item to drag during the MouseDown event.

The example also demonstrates using custom cursors for the drag-and-drop operation. The example requires that two cursor files, 3dwarro.cur and 3dwno.cur, exist in the application directory, for the custom drag and no-drop cursors, respectively. The custom cursors will be used if the UseCustomCursorsCheck CheckBox is checked. The custom cursors are set in the GiveFeedback event handler.

The keyboard state is evaluated in the DragOver event handler for the right ListBox, to determine what the drag operation will be based on state of the SHIFT, CTRL, ALT, or CTRL+ALT keys. The location in the ListBox where the drop would occur is also determined during the DragOver event. If the data to drop is not a String, then the DragEventArgs.Effect is set to None in DragDropEffects. Finally, the status of the drop is displayed in the DropLocationLabel Label.

The data to drop for the right ListBox is determined in the DragDrop event handler and the String value is added at the appropriate place in the ListBox. If the drag operation moves outside the bounds of the form, then the drag-and-drop operation is canceled in the QueryContinueDrag event handler.

This code excerpt demonstrates using the DragLeave event. See the DoDragDrop method for the complete code example.

void ListDragTarget_DragLeave( Object^ /*sender*/, System::EventArgs^ /*e*/ )
{
  // Reset the label text.
   DropLocationLabel->Text = "None";
}

private void ListDragTarget_DragLeave(object sender, EventArgs e)
{
    // Reset the label text.
    DropLocationLabel.Text = "None";
}

Private Sub ListDragTarget_DragLeave(ByVal sender As Object, ByVal e As EventArgs) Handles ListDragTarget.DragLeave
    ' Reset the label text.
    DropLocationLabel.Text = "None"
End Sub

Remarks

The DragLeave event is raised when the user drags the cursor out of the control or the user cancels the current drag-and-drop operation.

The following describes how and when events related to drag-and-drop operations are raised.

The DoDragDrop 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 GiveFeedback event is raised with the drag-and-drop effect specified. For a list of drag-and-drop effects, see the 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 DragLeave event is raised.

  • If the mouse enters another control, the DragEnter for that control is raised.

  • If the mouse moves but stays within the same control, the DragOver event is raised.

If there is a change in the keyboard or mouse button state, the 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 Action property of the event's QueryContinueDragEventArgs.

  • If the value of DragAction is Continue, the DragOver event is raised to continue the operation and the GiveFeedback event is raised with the new effect so appropriate visual feedback can be set. For a list of valid drop effects, see the DragDropEffects enumeration.

    Note

    The DragOver and GiveFeedback events are paired so that as the mouse moves across the drop target, the user is given the most up-to-date feedback on the mouse's position.

  • If the value of 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.

  • If the value of DragAction is Cancel, the DragLeave event is raised.

For more information about handling events, see Handling and Raising Events.

Applies to

See also