How to set icons for the windows forms treeview control ?

Question

I use imageList to store icons and I assign imageList to treeView, I use treeView1_DrawNode to change icon for treeView but this function does not run. See my photo and code below.

namespace TreeView
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
treeView1.ImageList = imageList1;
this.treeView1.DrawNode += new System.Windows.Forms.DrawTreeNodeEventHandler(this.treeView1_DrawNode);
dt = CreateTable(10);
CreateTreeView(dt, treeView1, true);
}
DataTable dt = new DataTable();
... //My code
private void treeView1_DrawNode(object sender, DrawTreeNodeEventArgs e)
{
if (e.Node.IsExpanded || e.Node.Nodes.Count < 1)
treeView1.ImageIndex = 0;
else
treeView1.ImageIndex = 1;
}
}

http://www.mediafire.com/file/iz4mvxfu9o0h863/treeView01.jpg

 

Why is the treeView1_DrawNode(...) function not running? How to change my treeView icons instead of +,- like a windows explorer treeview in win forms?