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Control.GiveFeedback Event

Occurs during a drag operation.

[Visual Basic]
Public Event GiveFeedback As GiveFeedbackEventHandler
[C#]
public event GiveFeedbackEventHandler GiveFeedback;
[C++]
public: __event GiveFeedbackEventHandler* GiveFeedback;

[JScript] In JScript, you can handle the events defined by a class, but you cannot define your own.

Event Data

The event handler receives an argument of type GiveFeedbackEventArgs containing data related to this event. The following GiveFeedbackEventArgs properties provide information specific to this event.

Property Description
Effect Gets the drag-and-drop operation feedback that is displayed.
UseDefaultCursors Gets or sets whether drag operation should use the default cursors that are associated with drag-drop effects.

Remarks

The GiveFeedback event is raised when a drag-and-drop operation is started. The GiveFeedback event allows the source of a drag event to modify the appearance of the mouse pointer in order to give the user visual feedback during a 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 is DragAction.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 is DragAction.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 is DragAction.Cancel, the DragLeave event is raised.

For more information about handling events, see Consuming Events.

Example

[Visual Basic, C#, C++] The following 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.

[Visual Basic, C#, C++] The example also demonstrates using custom cursors for the drag-and-drop operation. The example assumes 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.

[Visual Basic, C#, C++] The keyboard state is evaluated in the DragOver event handler for the right ListBox, to determine what the drag operation will be based upon 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 DragDropEffects.None. Finally, the status of the drop is displayed in the DropLocationLabel Label.

[Visual Basic, C#, C++] 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.

[Visual Basic, C#, C++] This code excerpt demonstrates using the GiveFeedback event. See the DoDragDrop method for the complete code example.

[Visual Basic] 
Private Sub ListDragSource_GiveFeedback(ByVal sender As Object, ByVal e As GiveFeedbackEventArgs) Handles ListDragSource.GiveFeedback

    ' Use custom cursors if the check box is checked.
    If (UseCustomCursorsCheck.Checked) Then

        ' Set the custom cursor based upon the effect.
        e.UseDefaultCursors = False
        If ((e.Effect And DragDropEffects.Move) = DragDropEffects.Move) Then
            Cursor.Current = MyNormalCursor
        Else
            Cursor.Current = MyNoDropCursor
        End If
    End If

End Sub

[C#] 
private void ListDragSource_GiveFeedback(object sender, System.Windows.Forms.GiveFeedbackEventArgs e) 
{
    // Use custom cursors if the check box is checked.
    if (UseCustomCursorsCheck.Checked) {

        // Sets the custom cursor based upon the effect.
        e.UseDefaultCursors = false;
        if ((e.Effect & DragDropEffects.Move) == DragDropEffects.Move)
            Cursor.Current = MyNormalCursor;
        else 
            Cursor.Current = MyNoDropCursor;
    }

}

[C++] 
private:
   void ListDragSource_GiveFeedback(Object* /*sender*/, 
      System::Windows::Forms::GiveFeedbackEventArgs* e)
   {

      // Use custom cursors if the check box is checked.
      if (UseCustomCursorsCheck->Checked) {

         // Sets the custom cursor based upon the effect.
         e->UseDefaultCursors = false;
         if ((e->Effect & DragDropEffects::Move) == DragDropEffects::Move)
            Cursor::Current = MyNormalCursor;
         else
            Cursor::Current = MyNoDropCursor;
      }

   }

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

See Also

Control Class | Control Members | System.Windows.Forms Namespace | OnGiveFeedback

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