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

Submitted by janobe on Sunday, April 27, 2014 - 09:47.

In this tutorial, I will show you how to drag/drop and copy in a Treeview by using Visual Basic 2008. I made this to show you not only a PictureBox or a TextBox can be drag and drop but also a treeview. Let’s begin: Open Visual Basic 2008, create a new Windows Application and drag the two Treeview in the Form. Name it “trview_left” and “trview_right”. first form

After that, click the two Treeviews and go to the properties. In the properties, click the events that look like a lightning symbol and double click the Drag/Drop event handler. And do this following code. Declare this constant variable above the sub procedure.

 
'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

Then, click the method name and choose the Drag/Enter events handler, and do this following code.

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

Go back to the method name again and choose the Item/Drag event handler and do this following code.

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

You can download the complete source code.

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