Create a custom handler assembly

Create a new class implementing IHttpHandler

Override the IsReusable property

Override ProcessRequest

Assign a file mapping to the handler in ASP.NET

Mention the handler in the <httpHandler> node of the application's Web.Config file

Assign a file mapping to the handler in IIS

Right-click on the virtual directory

Select Properties

Click the Configure button

Click the Add button

Add a new extension and map it to aspnet_isapi.dll

Create a simple handler

Select Web site | Add New Item

Select Generic Handler from the templates

Insert your own code for responding to the request