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

Drag/Drop functionality is an 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!