Perform Drag And Drop Operation On TreeView Node In C# .NET

This blog will show you how you can perform drag and drop operations on treeview control node using C#.Net in Windows application. So for this article first we will create a new windows application and add the below code on form load.

private void Form2_Load(object sender, EventArgs e)
      {
          treeView1 = new TreeView();

          this.SuspendLayout();

          // Initialize treeView1.
          treeView1.AllowDrop = true;
          treeView1.Dock = DockStyle.Fill;

          // Add nodes to treeView1.
          TreeNode node;
          for (int x = 0; x < 5; ++x)
          {
              // Add a root node to treeView1.
              node = treeView1.Nodes.Add(String.Format("Node{0}", x * 4));
              for (int y = 1; y < 6; ++y)
              {
                  // Add a child node to the previously added node.
                  node = node.Nodes.Add(String.Format("Node{0}", x * 4 + y));
              }
          }

          // Add event handlers for the required drag events.
          treeView1.ItemDrag += new ItemDragEventHandler(treeView1_ItemDrag);
          treeView1.DragEnter += new DragEventHandler(treeView1_DragEnter);
          treeView1.DragOver += new DragEventHandler(treeView1_DragOver);
          treeView1.DragDrop += new DragEventHandler(treeView1_DragDrop);

          // Initialize the form.
          this.ClientSize = new Size(292, 273);
          this.Controls.Add(treeView1);

          this.ResumeLayout(false);
      }

In the above code I have created nodes of tree view. Now we will perform the operation for the drag and drop feature. First create the tree view control treeView1_ItemDrag event and add the below code. 

private void treeView1_ItemDrag(object sender, ItemDragEventArgs e)
      {
          // Move the dragged node when the left mouse button is used.
          if (e.Button == MouseButtons.Left)
          {
              DoDragDrop(e.Item, DragDropEffects.Move);
          }

          // Copy the dragged node when the right mouse button is used.
          else if (e.Button == MouseButtons.Right)
          {
              DoDragDrop(e.Item, DragDropEffects.Copy);
          }
      }

After this we will create the treeView1_DragEnter event. 

private void treeView1_DragEnter(object sender, DragEventArgs e)
      {
          e.Effect = e.AllowedEffect;
      }

Now we will create the treeView1_DragOver event, 

private void treeView1_DragOver(object sender, DragEventArgs e)
{
    // Retrieve the client coordinates of the mouse position.
    Point targetPoint = treeView1.PointToClient(new Point(e.X, e.Y));

    // Select the node at the mouse position.
    treeView1.SelectedNode = treeView1.GetNodeAt(targetPoint);
}

Now we will create the treeView1_DragDrop event, 

private void treeView1_DragDrop(object sender, DragEventArgs e)
       {
           // Retrieve the client coordinates of the drop location.
           Point targetPoint = treeView1.PointToClient(new Point(e.X, e.Y));

           // Retrieve the node at the drop location.
           TreeNode targetNode = treeView1.GetNodeAt(targetPoint);

           // Retrieve the node that was dragged.
           TreeNode draggedNode = (TreeNode)e.Data.GetData(typeof(TreeNode));

           // Confirm that the node at the drop location is not
           // the dragged node or a descendant of the dragged node.
           if (!draggedNode.Equals(targetNode) && !ContainsNode(draggedNode, targetNode))
           {
               // If it is a move operation, remove the node from its current
               // location and add it to the node at the drop location.
               if (e.Effect == DragDropEffects.Move)
               {
                   draggedNode.Remove();
                   targetNode.Nodes.Add(draggedNode);
               }

               // If it is a copy operation, clone the dragged node
               // and add it to the node at the drop location.
               else if (e.Effect == DragDropEffects.Copy)
               {
                   targetNode.Nodes.Add((TreeNode)draggedNode.Clone());
               }

               // Expand the node at the location
               // to show the dropped node.
               targetNode.Expand();
           }

       }

After that we will use the below function to perform parent child relation, 

private bool ContainsNode(TreeNode node1, TreeNode node2)
     {
         // Check the parent node of the second node.
         if (node2.Parent == null) return false;
         if (node2.Parent.Equals(node1)) return true;

         // If the parent node is not null or equal to the first node,
         // call the ContainsNode method recursively using the parent of
         // the second node.
         return ContainsNode(node1, node2.Parent);
     }

Now we are done. Run the code to check the output.