C#

using System;<br />
using System.Collections.Generic;<br />
using System.ComponentModel;<br />
using System.Data;<br />
using System.Drawing;<br />
using System.Text;<br />
using System.Windows.Forms;<br />
<br />
namespace DragAndDropTest<br />
{<br />
    public partial class Form1 : Form<br />
    {<br />
        private TreeNode previousTarget;<br />
<br />
        private void FunctionThatFailes()<br />
        {<br />
            throw new ApplicationException("Something is wrong");<br />
        }<br />
<br />
        public Form1()<br />
        {<br />
            InitializeComponent();<br />
        }<br />
<br />
        private void treeView1_ItemDrag(object sender, ItemDragEventArgs e)<br />
        {<br />
            treeView1.DoDragDrop(<br />
                treeView1.SelectedNode, DragDropEffects.Move);<br />
        }<br />
<br />
        private void treeView1_DragDrop(object sender, DragEventArgs e)<br />
        {<br />
            TreeNode source = e.Data.GetData(typeof(TreeNode)) as TreeNode;<br />
            TreeNode target = previousTarget;<br />
            ResetPreviousTarget();<br />
            FunctionThatFailes();<br />
            target.Text += source.Text;<br />
        }<br />
<br />
        private void ResetPreviousTarget()<br />
        {<br />
            if (previousTarget != null) {<br />
                previousTarget.ForeColor = SystemColors.WindowText;<br />
                previousTarget.BackColor = SystemColors.Window;<br />
                previousTarget = null;<br />
            }<br />
        }<br />
<br />
        private void treeView1_DragOver(object sender, DragEventArgs e)<br />
        {<br />
            ResetPreviousTarget();<br />
<br />
            if (e.Data.GetData(typeof(TreeNode)) != treeView1.SelectedNode) {<br />
                e.Effect = DragDropEffects.None;<br />
                return;<br />
            }<br />
<br />
            TreeNode target = treeView1.GetNodeAt(<br />
                treeView1.PointToClient(Control.MousePosition));<br />
            if (target == null || target == treeView1.SelectedNode) {<br />
                e.Effect = DragDropEffects.None;<br />
                return;<br />
            }<br />
<br />
            e.Effect = DragDropEffects.Move;<br />
<br />
            if (target == previousTarget) {<br />
                return;<br />
            }<br />
<br />
            previousTarget = target;<br />
<br />
            target.ForeColor = SystemColors.InactiveCaptionText;<br />
            target.BackColor = SystemColors.InactiveCaption;<br />
        }<br />
<br />
        private void Form1_Load(object sender, EventArgs e)<br />
        {<br />
            treeView1.AllowDrop = true;<br />
        }<br />
<br />
        private void button1_Click(object sender, EventArgs e)<br />
        {<br />
            FunctionThatFailes();<br />
        }<br />
    }<br />
}

<br />
XML...<br />
<Root><br />
   <MajorKey att="MAJattribute1"><br />
      <MinorKey att="MINattribute1"><br />
          <Value>value1</Value><br />
      </MinorKey><br />
      <MinorKey att="MINattribute2"><br />
         <Value>value2</value><br />
      </MinorKey><br />
   </MajorKey><br />
   <MajorKey att="MAJattribute2"><br />
      <MinorKey att="MINattribute3"><br />
          <Value>value3</Value><br />
      </MinorKey><br />
      <MinorKey att="MINattribute4"><br />
         <Value>value4</value><br />
      </MinorKey><br />
   </MajorKey><br />
</Root><br />