Custom Javascript Ajax for ASP.NET
<p>I've written some basic Javascript functions and would like to learn how to enable asynchronous postbacks within a C# 4.0/ASP.net project using this JS code.  </p>

<p>For example, I have a script that increments a number when clicked.  When clicked again, the number is decremented.  I basically load the number from a database, then hide one <code>&lt;span&gt;</code> and show another with the corresponding decremented number on click.  This is not complicated javascript; its a simple example.  Now when I click the button I want to send this increment/decrement call back to the server to update the database's number.</p>

<p>I realize that I can accomplish something akin to this example using the AJAX Control Toolkit's toggle button.  I, however, want to know how to use my OWN javascript to create AJAX functionality.</p>

<p>How do I accomplish this using C# and my custom Javascript code?</p>

<p>I'm not opposed to using the ASP.net AJAX library, I just don't want to use a ready built control.  I want to learn the process of creating my own AJAX functionality.  I would presume that I will have to use an <code>asp:UpdatePanel</code>, but I don't know how to call C# functions from the client side.</p>

<p>My javascript is not jQuery, in fact I want nothing to do with jQuery until I learn more about javascript and this process.</p>
