Uploading files using ASP.NET Framework 1.0 / 2.0 / 3.0 is pretty easy. Without much error handling, all we need is a couple of lines of code to upload a file to the web server. Read my article which explains how to upload files using ASP.NET which was written four years back. AJAX is playing a greater role these days in every webpage that pops up. Uploading files using ASP.NET AJAX is not a straight forward one. Those who do know about AJAX, it is used to update some portions/sections of a web page without affecting other sections. In other words, if you do want to refresh your web page on a button click but you still want to update the content of your web page, then you should use AJAX.