Drag/Drop and Copy Control in a TreeView Using Visual Basic 2008

 
'DECLARE A CONSTANT VARIABLE 
'IT IS USED FOR DETECTING THE CTRL KEY WHETHER THE CTRL KEY WAS PRESSED OR NOT DURING THE DRAG OPERATION
Const mask_ctrl As Int32 = 8

Private Sub TreeView_DragDrop(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles trview_left.DragDrop, trview_right.DragDrop
 
        'SET A VARIABLE TO HOLDS THE NODE TO BE DRAGGED
        Dim nodeorigination As TreeNode = CType(e.Data.GetData("System.Windows.Forms.TreeNode"), TreeNode)
 
        'GETDATAPRESENT IS A BIT DIFFERENT FROM A TREEVIEW AND PICTUREBOX CONTROL.
        'THE TREENODE IS NOT INCLUDED IN THE DATAFORMATS CLASS. THAT'S WHY IT'S NOT A PREDEFINED TYPE 
        'ONE OF THE GETDATAPRESENT CONTAINS A STRING THAT SPECIFY THE TYPE.
        If e.Data.GetDataPresent("System.Windows.Forms.TreeNode", False) Then
            Dim pnt As Point
            Dim distination_node As TreeNode
 
            'POINTTOCLIENT IS USED TO COMPUTE THE LOCATION OF THE MOUSE OVER THE DESTINATION TREEVIEW
            pnt = CType(sender, TreeView).PointToClient(New Point(e.X, e.Y))
            'POINT IS USED TO GET THE CLOSEST NODE IN THE DESTINATION TREEVIEW
            distination_node = CType(sender, TreeView).GetNodeAt(pnt)
 
            'IF THE NEW NODE WAS NOT DROPPED DIRECTLY AT THE TOP OF THE NODE, 
            'THEN THE RESULT OF THE DESTINATIONNODE WILL BE NOTHING
            If distination_node IsNot Nothing Then
                'IF THE ORIGINAL NODE AND DISTINATION NODE ARE THE SAME, THE THE NODE WOULD DISAPPEAR.
                'THIS CODE INSURES THAT IT WILL NOT HAPPEN.                 
                If Not distination_node.TreeView Is nodeorigination.TreeView Then
                    distination_node.Nodes.Add(CType(nodeorigination.Clone, TreeNode))
                    'EMPHASIZE PARENT NOT WHEN ADDING THE NEW NODE, WITHOUT THIS , ONLY THE a+ SYMBOL WILL APPEAR.
                    distination_node.Expand()
 
                    If (e.KeyState And maskctrl) <> maskctrl Then 'CHECKING THE CTRL KEY WAS NOT PRESSED
                        nodeorigination.Remove() 'REMOVE THE NODE 
                    End If
                End If
            End If
        End If
    End Sub

Private Sub TreeView_DragEnter(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles trview_left.DragEnter, trview_right.DragEnter
 
        If (e.Data.GetDataPresent("System.Windows.Forms.TreeNode")) Then 'CHECKING THE DRAG CONTENT TO BE SURE THAT IT IS THE CORRECT TYPE.
 
            If (e.KeyState And maskctrl) = maskctrl Then 'CHECKINKG IF THE CTRL KEY WAS PRESSED.
                'IF IT WAS PRESSED
                e.Effect = DragDropEffects.Copy 'PERFORM COPY
            Else
                'IF IT WAS NOT PRESSED
                e.Effect = DragDropEffects.Move 'PERFORM A MOVE
            End If
        Else
            'REJECT THE DROP
            e.Effect = DragDropEffects.None
        End If
    End Sub

Private Sub TreeView_ItemDrag(ByVal sender As System.Object, ByVal e As System.Windows.Forms.ItemDragEventArgs) Handles trview_left.ItemDrag, trview_right.ItemDrag
        If e.Button = Windows.Forms.MouseButtons.Left Then
            'PERFORM THE DRAG AND DROP OPERATION.
            DoDragDrop(e.Item, DragDropEffects.Move Or DragDropEffects.Copy)
        End If
    End Sub