There is a known problem with TreeView checkboxes in ASP.NET: they can't do AutoPostBack. So I've solved this problem like this:

<script language="javascript" type="text/javascript">

function postbackOnCheck()
var o = window.event.srcElement;
if (o.tagName == 'INPUT' && o.type == 'checkbox' &&
o.name != null && o.name.indexOf('CheckBox') > -1)


<asp:TreeView onclick="postbackOnCheck()" ID="treeContent"
runat="server"> ... And so on ... </TreeView> This way I get full postback each time the user checks\unchecks the checkbox.

But now I want to modify this code in order to make use of AJAX: I don't want the FULL postback, but I only want the tree itself to be updated. Of course, I've started by placing it inside the UpdatePanel. But what now? Can somebody help me with this issue?