DragDropEffects Enum
Definition
Important
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Specifies the possible effects of a drag-and-drop operation.
This enumeration supports a bitwise combination of its member values.
public enum class DragDropEffects[System.Flags]
public enum DragDropEffects[<System.Flags>]
type DragDropEffects = Public Enum DragDropEffects- Inheritance
- Attributes
Fields
| Name | Value | Description |
|---|---|---|
| Scroll | -2147483648 | The target can be scrolled while dragging to locate a drop position that is not currently visible in the target. |
| All | -2147483645 | |
| None | 0 | The drop target does not accept the data. |
| Copy | 1 | The data from the drag source is copied to the drop target. |
| Move | 2 | The data from the drag source is moved to the drop target. |
| Link | 4 | The data from the drag source is linked to the drop target. |
Examples
The following example demonstrates using the DragDropEffects enumeration when the user moves the mouse over the drop target during a drag-and-drop operation. This example is part of a larger example provided for the Control.DoDragDrop method.
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( System::String::typeid ) )
{
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 = CTRL + 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) )
{
// CTRL 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( "Drops before item # ", (indexOfItemUnderMouseToDrop + 1) );
}
else
DropLocationLabel->Text = "Drops at the end.";
}
private void ListDragTarget_DragOver(object sender, 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 = CTRL + 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)
{
// CTRL 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.";
}
}
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 = CTRL + 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
' CTRL 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
Remarks
This enumeration is used by the DragEventArgs, GiveFeedbackEventArgs, and Control classes.
You can use DragDropEffects to display different mouse pointers for drag-and-drop operations. For example, you can display a plus symbol for a Copy drag-and-drop operation, an arrow symbol for a Move drag-and-drop operation, or a red circle with a line through it symbol for a None drag-and-drop operation.
If you want to drop data at a position in the target that is not currently visible, you could scroll the target while dragging. If a target does not support scrolling, you must make sure that the drop position is visible in the target before you begin the drag-and-drop operation. The following are some scenarios when you might want to scroll a target:
You're dragging text into a document, and you want to drop the text at a position not visible in the document window.
You're dragging a file into a file tree, and you want to drop the file on a node not visible in the file tree.
