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DragDropEffects Enumeration

Specifies the effects of a drag-and-drop operation.

This enumeration has a FlagsAttribute attribute that allows a bitwise combination of its member values.

[Visual Basic]
<Flags>
<Serializable>
Public Enum DragDropEffects
[C#]
[Flags]
[Serializable]
public enum DragDropEffects
[C++]
[Flags]
[Serializable]
__value public enum DragDropEffects
[JScript]
public
   Flags
 Serializable
enum DragDropEffects

Remarks

This enumeration is used by the following classes: DragEventArgs, GiveFeedbackEventArgs, and Control.

Members

Member name Description Value
All The data is copied, removed from the drag source, and scrolled in the drop target. -2147483645
Copy The data is copied to the drop target. 1
Link The data from the drag source is linked to the drop target. 4
Move The data from the drag source is moved to the drop target. 2
None The drop target does not accept the data. 0
Scroll Scrolling is about to start or is currently occurring in the drop target. -2147483648

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 DragDropEffects enumeration. See the DoDragDrop method for the complete code example.

[Visual Basic] 
Private Sub ListDragTarget_DragOver(ByVal sender As Object, ByVal e As DragEventArgs) Handles ListDragTarget.DragOver
    ' Determine whether string data exists in the drop data. If not, then
    ' the drop effect reflects that the drop cannot occur.
    If Not (e.Data.GetDataPresent(GetType(System.String))) Then

        e.Effect = DragDropEffects.None
        DropLocationLabel.Text = "None - no string data."
        Return
    End If

    ' Set the effect based upon the KeyState.
    If ((e.KeyState And (8 + 32)) = (8 + 32) And _
        (e.AllowedEffect And DragDropEffects.Link) = DragDropEffects.Link) Then
        ' KeyState 8 + 32 = CTL + ALT

        ' Link drag and drop effect.
        e.Effect = DragDropEffects.Link

    ElseIf ((e.KeyState And 32) = 32 And _
        (e.AllowedEffect And DragDropEffects.Link) = DragDropEffects.Link) Then

        ' ALT KeyState for link.
        e.Effect = DragDropEffects.Link

    ElseIf ((e.KeyState And 4) = 4 And _
        (e.AllowedEffect And DragDropEffects.Move) = DragDropEffects.Move) Then

        ' SHIFT KeyState for move.
        e.Effect = DragDropEffects.Move

    ElseIf ((e.KeyState And 8) = 8 And _
        (e.AllowedEffect And DragDropEffects.Copy) = DragDropEffects.Copy) Then

        ' CTL KeyState for copy.
        e.Effect = DragDropEffects.Copy

    ElseIf ((e.AllowedEffect And DragDropEffects.Move) = DragDropEffects.Move) Then

        ' By default, the drop action should be move, if allowed.
        e.Effect = DragDropEffects.Move

    Else
        e.Effect = DragDropEffects.None
    End If

    ' Gets the index of the item the mouse is below. 

    ' The mouse locations are relative to the screen, so they must be 
    ' converted to client coordinates.

    indexOfItemUnderMouseToDrop = _
        ListDragTarget.IndexFromPoint(ListDragTarget.PointToClient(New Point(e.X, e.Y)))

    ' Updates the label text.
    If (indexOfItemUnderMouseToDrop <> ListBox.NoMatches) Then

        DropLocationLabel.Text = "Drops before item #" & (indexOfItemUnderMouseToDrop + 1)
    Else
        DropLocationLabel.Text = "Drops at the end."
    End If

End Sub

[C#] 
private void ListDragTarget_DragOver(object sender, System.Windows.Forms.DragEventArgs e) 
{

    // Determine whether string data exists in the drop data. If not, then
    // the drop effect reflects that the drop cannot occur.
    if (!e.Data.GetDataPresent(typeof(System.String))) {

        e.Effect = DragDropEffects.None;
        DropLocationLabel.Text = "None - no string data.";
        return;
    }

    // Set the effect based upon the KeyState.
    if ((e.KeyState & (8+32)) == (8+32) && 
        (e.AllowedEffect & DragDropEffects.Link) == DragDropEffects.Link) {
        // KeyState 8 + 32 = CTL + ALT

        // Link drag and drop effect.
        e.Effect = DragDropEffects.Link;

    } else if ((e.KeyState & 32) == 32 && 
        (e.AllowedEffect & DragDropEffects.Link) == DragDropEffects.Link) {

        // ALT KeyState for link.
        e.Effect = DragDropEffects.Link;

    } else if ((e.KeyState & 4) == 4 && 
        (e.AllowedEffect & DragDropEffects.Move) == DragDropEffects.Move) {

        // SHIFT KeyState for move.
        e.Effect = DragDropEffects.Move;

    } else if ((e.KeyState & 8) == 8 && 
        (e.AllowedEffect & DragDropEffects.Copy) == DragDropEffects.Copy) {

        // CTL KeyState for copy.
        e.Effect = DragDropEffects.Copy;

    } else if ((e.AllowedEffect & DragDropEffects.Move) == DragDropEffects.Move)  {

        // By default, the drop action should be move, if allowed.
        e.Effect = DragDropEffects.Move;

    } else
        e.Effect = DragDropEffects.None;
        
    // Get the index of the item the mouse is below. 

    // The mouse locations are relative to the screen, so they must be 
    // converted to client coordinates.

    indexOfItemUnderMouseToDrop = 
        ListDragTarget.IndexFromPoint(ListDragTarget.PointToClient(new Point(e.X, e.Y)));

    // Updates the label text.
    if (indexOfItemUnderMouseToDrop != ListBox.NoMatches){

        DropLocationLabel.Text = "Drops before item #" + (indexOfItemUnderMouseToDrop + 1);
    } else
        DropLocationLabel.Text = "Drops at the end.";

}

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

      // Determine whether string data exists in the drop data. If not, then
      // the drop effect reflects that the drop cannot occur.
      if (!e->Data->GetDataPresent(__typeof(System::String))) {

         e->Effect = DragDropEffects::None;
         DropLocationLabel->Text = S"None - no string data.";
         return;
      }

      // Set the effect based upon the KeyState.
      if ((e->KeyState & (8+32)) == (8+32) &&
         (e->AllowedEffect & DragDropEffects::Link) == DragDropEffects::Link) 
      {
         // KeyState 8 + 32 = CTL + ALT

         // Link drag and drop effect.
         e->Effect = DragDropEffects::Link;

      } else if ((e->KeyState & 32) == 32 &&
         (e->AllowedEffect & DragDropEffects::Link) == DragDropEffects::Link)
      {

         // ALT KeyState for link.
         e->Effect = DragDropEffects::Link;

      } else if ((e->KeyState & 4) == 4 &&
         (e->AllowedEffect & DragDropEffects::Move) == DragDropEffects::Move)
      {
         // SHIFT KeyState for move.
         e->Effect = DragDropEffects::Move;

      } else if ((e->KeyState & 8) == 8 &&
         (e->AllowedEffect & DragDropEffects::Copy) == DragDropEffects::Copy)
      {
         // CTL KeyState for copy.
         e->Effect = DragDropEffects::Copy;

      } else if ((e->AllowedEffect & DragDropEffects::Move) == DragDropEffects::Move)
      {
         // By default, the drop action should be move, if allowed.
         e->Effect = DragDropEffects::Move;

      } else
         e->Effect = DragDropEffects::None;

      // Get the index of the item the mouse is below.

      // The mouse locations are relative to the screen, so they must be
      // converted to client coordinates.

      indexOfItemUnderMouseToDrop =
         ListDragTarget->IndexFromPoint(
         ListDragTarget->PointToClient(Point(e->X, e->Y)));

      // Updates the label text.
      if (indexOfItemUnderMouseToDrop != ListBox::NoMatches) {

         DropLocationLabel->Text = 
            String::Concat(S"Drops before item # ",
            __box( (indexOfItemUnderMouseToDrop + 1)));
      } else
         DropLocationLabel->Text = S"Drops at the end.";

   }

[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

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)

See Also

System.Windows.Forms Namespace | DragEventArgs | GiveFeedbackEventArgs

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