What is an .ashx?

“Most .NET Web Applications are built using .ASPX and ASCX (User Controls) Files. However, ASP.NET provides an easy way to build HTTP Handlers via .ASHX Files. You might want to use HTTP Handlers when the output of your application isn’t going to a web browser. For example, perhaps the output is xml that will be cosumed by some other type of client. HTTP Handlers implemented on IIS can be either ISAPI Extensions or ISAPI Filters. ISAPI Extensions are implemented as a windows dll and are the target of an HTTP Request. ISAPI Filters sit between the client and the web server intercepting all http requests.”

Quoted from:
Referance:”Debugging an HTTP Handler (*.ashx) in ASP.NET 2.0 By Dina Fleet Berry”, http://www.15seconds.com/issue/060406.htm
An Implementation:
“Dynamically Changing the Contents of Mail Signature Using RSS Feeds in C#”,