DragAction Enumeration
Specifies how and if a drag-and-drop operation should continue.
[Visual Basic] <Serializable> <ComVisible(True)> Public Enum DragAction [C#] [Serializable] [ComVisible(true)] public enum DragAction [C++] [Serializable] [ComVisible(true)] __value public enum DragAction [JScript] public Serializable ComVisible(true) enum DragAction
Remarks
This enumeration is used by QueryContinueDragEventArgs.
Members
| Member name | Description |
|---|---|
| Cancel | The operation is canceled with no drop message. |
| Continue | The operation will continue. |
| Drop | The operation will stop with a drop. |
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 DragAction enumeration. See the DoDragDrop method for the complete code example.
[Visual Basic] Private Sub ListDragSource_QueryContinueDrag(ByVal sender As Object, ByVal e As QueryContinueDragEventArgs) Handles ListDragSource.QueryContinueDrag ' Cancel the drag if the mouse moves off the form. Dim lb as ListBox = CType(sender, System.Windows.Forms.ListBox) If Not (lb is nothing) Then Dim f as Form = lb.FindForm() ' Cancel the drag if the mouse moves off the form. The screenOffset ' takes into account any desktop bands that may be at the top or left ' side of the screen. If (((Control.MousePosition.X - screenOffset.X) < f.DesktopBounds.Left) Or _ ((Control.MousePosition.X - screenOffset.X) > f.DesktopBounds.Right) Or _ ((Control.MousePosition.Y - screenOffset.Y) < f.DesktopBounds.Top) Or _ ((Control.MousePosition.Y - screenOffset.Y) > f.DesktopBounds.Bottom)) Then e.Action = DragAction.Cancel End If End if End Sub [C#] private void ListDragSource_QueryContinueDrag(object sender, System.Windows.Forms.QueryContinueDragEventArgs e) { // Cancel the drag if the mouse moves off the form. ListBox lb = sender as ListBox; if (lb != null) { Form f = lb.FindForm(); // Cancel the drag if the mouse moves off the form. The screenOffset // takes into account any desktop bands that may be at the top or left // side of the screen. if (((Control.MousePosition.X - screenOffset.X) < f.DesktopBounds.Left) || ((Control.MousePosition.X - screenOffset.X) > f.DesktopBounds.Right) || ((Control.MousePosition.Y - screenOffset.Y) < f.DesktopBounds.Top) || ((Control.MousePosition.Y - screenOffset.Y) > f.DesktopBounds.Bottom)) { e.Action = DragAction.Cancel; } } } [C++] private: void ListDragSource_QueryContinueDrag(Object* sender, System::Windows::Forms::QueryContinueDragEventArgs* e) { // Cancel the drag if the mouse moves off the form. ListBox* lb = dynamic_cast<ListBox*>(sender); if (lb != 0) { Form* f = lb->FindForm(); // Cancel the drag if the mouse moves off the form. The screenOffset // takes into account any desktop bands that may be at the top or left // side of the screen. if (((Control::MousePosition.X - screenOffset.X) < f->DesktopBounds.Left) || ((Control::MousePosition.X - screenOffset.X) > f->DesktopBounds.Right) || ((Control::MousePosition.Y - screenOffset.Y) < f->DesktopBounds.Top) || ((Control::MousePosition.Y - screenOffset.Y) > f->DesktopBounds.Bottom)) { e->Action = DragAction::Cancel; } } }
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Requirements
Namespace: System.Windows.Forms
Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family
Assembly: System.Windows.Forms (in System.Windows.Forms.dll)