C# IHttpHandler

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C# - IHttpHandler in ASP.NET

IHttpHandler is an interface in the ASP.NET framework that provides a means to process requests in custom ways. Whenever an ASP.NET application receives a request, it's handed over to an appropriate handler to generate the response. This is a fundamental part of the ASP.NET request processing pipeline.

Implementing the IHttpHandler interface gives you fine-grained control over the response, allowing for very efficient processing, which is especially beneficial in scenarios where the standard page lifecycle would be overkill, such as when generating an image on the fly, serving a file based on dynamic criteria, or generating a real-time data response.

Properties and Methods:

IsReusable: A property that gets a value indicating whether another request can use the IHttpHandler instance.
ProcessRequest(HttpContext context): The method which processes the incoming HTTP request. You implement your custom logic here.

Example:

Imagine you want to create a custom handler that simply responds with the current server time.

Create a class that implements IHttpHandler:


using System;
using System.Web;

public class CurrentTimeHandler : IHttpHandler
{
    public bool IsReusable
    {
        get { return false; }
    }

    public void ProcessRequest(HttpContext context)
    {
        context.Response.ContentType = "text/plain";
        context.Response.Write(DateTime.Now.ToString());
    }
}

Register the handler in the web.config:


<configuration>
   <system.web>
      <httpHandlers>
         <add verb="*" path="CurrentTime.ashx" type="Namespace.CurrentTimeHandler, AssemblyName"/>
      </httpHandlers>
   </system.web>
</configuration>

Now, when someone accesses "CurrentTime.ashx" on your server, they'll receive the current server time as a plain text response.

Notes:

IHttpHandler is a low-level approach. For most web application scenarios, using ASP.NET Web Pages, MVC, or Web API would be more appropriate.
ASP.NET also provides an interface named IHttpAsyncHandler that allows for asynchronous handling of requests.
If you create reusable handlers, make sure to return true for the IsReusable property. However, ensure that your handler is thread-safe if it's reused.