      private void Append_Click(object sender, EventArgs e)
        {
            TreeNode node;
            node = treeView1.SelectedNode;
            if (node == null)
            {
                MessageBox.Show("Please  Select a Node");
                return;
            }
            if (textBox1.Text == "")
                MessageBox.Show("Please Enter Node Name");
            node.Nodes.Add(textBox1.Text);
        }

      
