single select asp.net treeview

< asp:TreeView ID="TreeView1" runat="server">

script type="text/javascript" >
function client_OnTreeNodeChecked(event, tree) {
var TreeNode = event.srcElement || event.target;
if (TreeNode.tagName == "INPUT" && TreeNode.type == "checkbox") {
if (TreeNode.checked) {
uncheckOthers(TreeNode.id, tree);
}
}
}

function uncheckOthers(id, tree) {
var elements = document.getDocumentById(tree).getElementsByTagName('input');
// loop through all input elements in form
for (var i = 0; i < elements.length; i++) {
if (elements.item(i).type == "checkbox") {
if (elements.item(i).id != id) {
elements.item(i).checked = false;
}
}
}
}
}
script

private void Page_PreRender(object sender, EventArgs e)
{
TreeView1.Attributes.Add("OnClick", "client_OnTreeNodeChecked(event, '" + TreeView1.ClientID + "')");
}