Custom ASP.NET Processing with HTTP Handlers
HTTP handlers are ASP.NET components that run when they are requested in a browser and that return dynamically created information. (An ASP.NET Web page is an example of one type of HTTP handler.) You can use HTTP handlers to create any type of process that needs to return information to users that is not an HTML page. This section describes how to create and register HTTP handlers and provides examples of a synchronous handler, an asynchronous handler, and a handler factory.