Call a server function from javascript

[d00_ape]

How can I force a postback and call a codebehind funktion from javascript?
I want to do something like this:

aspx-file
<script type="text/javascript">
function OnRowSelecting(sender, args)
{
ServerFunc();
}
</script>

Codebehind c# file
private void ServerFunc()
{
//…
}

[dannystommen]

http://ajax.schwarz-interactive.de/download/ajaxsample.zip

download the zip. In the zip there's a Word document with tutorial