public delegate void treeinvoke();
private void UpdateTreeView()
{
  MessageBox.Show(System.Threading.Thread.CurrentThread.Name);
}
private void button1_Click(object sender, System.EventArgs e)
{
  System.Threading.Thread.CurrentThread.Name = "UIThread";
  treeView1.BeginInvoke(new treeinvoke(UpdateTreeView));
}

public delegate void treeinvoke();
private void UpdateTreeView()
{
  MessageBox.Show(Thread.CurrentThread.Name);
}
private void button1_Click(object sender, System.EventArgs e)
{
  Thread.CurrentThread.Name = "UIThread";
  Thread th = new Thread(new ThreadStart(StartThread));
  th.Start();
}
private void StartThread()
{
  Thread.CurrentThread.Name = "Work Thread";
  treeView1.BeginInvoke(new treeinvoke(UpdateTreeView));
}

private void button1_Click_(object sender, System.EventArgs e)
{
  TreeNode tn;
  for(int i=0;i<100000;i++)
  {
    tn=new TreeNode (i.ToString());
    this.treeView1.Nodes[0].Nodes.Add(tn);
    if (i0 == 0) Application.DoEvents();
  }
}