ashx

The .ashx file extension is associated with ASP.NET HTTP Handlers. These are server-side executable files that process HTTP requests and generate responses. Unlike traditional ASP.NET pages (.aspx) which typically render HTML, ASHX handlers are designed for more specific tasks. They can be used to generate various types of content, including images, plain text, XML, JSON, or any other binary or text-based data.

When a web server encounters an .ashx file, it passes the request to the registered ASP.NET HTTP Handler. This handler, written in a .NET language like C# or VB.NET, executes custom code. The handler's primary responsibility is to interact with the request, perform operations, and then write the output to the response stream. This makes them highly flexible for scenarios where direct control over the response is needed, such as creating dynamic images on the fly, serving files with specific content types, or implementing custom API endpoints.

ASHX handlers offer a lightweight alternative to full ASP.NET pages when complex UI rendering is not required. They can be a valuable tool for optimizing performance and simplifying the codebase for specific functionalities within an ASP.NET web application. The underlying mechanism involves implementing the `IHttpHandler` interface in a .NET class.