How to Perform Drag-Drop Operations on TreeView Control in Windows Forms

Drag/Drop functionality is a ease to end user in each and every technology and almost every user is comfortable using the drag-drop feature. In this post we will see how to perform drag and drop operation of nodes in a single TreeView control. There are few events that we will be working with. They are – ItemDrag(), DragEnter() and DragDrop(). Apart from these, we will also use some inbuilt functions that facilitate drag/drop operations on Windows forms. So, Let’s get started. To create a draggable/drop-able Treeview control on windows forms, we will use the steps mentioned below :

• Set the AllowDrop property of TreeView control to True.
• Populate the TreeView with some nodes. I am here filling the nodes with some sample data
  
  private function LoadData()
  {
      for (int i = 0; i < 5; i++)
     {
         TreeNode node = new TreeNode("Node " + i);
          for (int j = 0; j < 3; j++)
         {
             TreeNode n1 = new TreeNode("Sub-node :" + i + " - " + j);
             node.Nodes.Add(n1);
         }
         treeView1.Nodes.Add(node);
     }
  }
   
• Handle the ItemDrag() event handler of the TreeView and write the code below:
  
  private void treeView1_ItemDrag(object sender, ItemDragEventArgs e)
  {
      DoDragDrop(e.Item, DragDropEffects.Move);
  }
   
• Handle the DragEnter() event handler of the TreeView and write the code below:
  
  private void treeView1_DragEnter(object sender, ItemDragEventArgs e)
  {
      e.Effect = DragDropEffects.Move;
  }
   
• Handle the DragDrop() event handler of the TreeView and write the code below:
  
  private void treeView1_DragDrop(object sender, ItemDragEventArgs e)
  {
      TreeNode NewNode;
      if (e.Data.GetDataPresent("System.Windows.Forms.TreeNode", false))
     {
            Point pt = ((TreeView)sender).PointToClient(new Point(e.X, e.Y));
           TreeNode DestinationNode = ((TreeView)sender).GetNodeAt(pt);
           NewNode = (TreeNode)e.Data.GetData("System.Windows.Forms.TreeNode");
           DestinationNode.Nodes.Add((TreeNode)NewNode.Clone());
           DestinationNode.Expand();
          //Remove Original Node
          NewNode.Remove();
     }
  }
   
• You're done.
• Execute the application and try dragging/dropping the nodes on the TreeView control.

Keep learning and sharing! Cheers!