What is an HttpHandler in ASP.NET? Why and how is it used?
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In the simplest terms, an ASP.NET HttpHandler is a class that implements the System.Web.IHttpHandler interface.
ASP.NET HTTPHandlers are responsible for intercepting requests made to your ASP.NET web application server. They run as processes in response to a request made to the ASP.NET Site. The most common handler is an ASP.NET page handler that processes .aspx files. When users request an .aspx file, the request is processed by the page through the page handler.
ASP.NET offers a few default HTTP handlers:
You can create your own custom HTTP handlers that render custom output to the browser. Typical scenarios for HTTP Handlers in ASP.NET are for example
You implement the IHttpHandler interface to create a synchronous handler and the IHttpAsyncHandler interface to create an asynchronous handler. The interfaces require you to implement the ProcessRequest method and the IsReusable property.
The ProcessRequest method handles the actual processing for requests made, while the Boolean IsReusable property specifies whether your handler can be pooled for reuse (to increase performance) or whether a new handler is required for each request.
An HttpHandler (or IHttpHandler) is basically anything that is responsible for serving content. An ASP.NET page (aspx) is a type of handler.
You might write your own, for example, to serve images etc from a database rather than from the web-server itself, or to write a simple POX service (rather than SOAP/WCF/etc)
An ASP.NET HTTP handler is the process (frequently referred to as the "endpoint") that runs in response to a request made to an ASP.NET Web application. The most common handler is an ASP.NET page handler that processes .aspx files. When users request an .aspx file, the request is processed by the page through the page handler. You can create your own HTTP handlers that render custom output to the browser.
An HttpHandler (or IHttpHandler) is basically anything that is responsible for serving content. An ASP.NET page (aspx) is a type of handler.
You might write your own, for example, to serve images etc from a database rather than from the web-server itself, or to write a simple POX service (rather than SOAP/WCF/etc)
An ASP.NET HTTP handler is the process (frequently referred to as the "endpoint") that runs in response to a request made to an ASP.NET Web application. The most common handler is an ASP.NET page handler that processes .aspx files. When users request an .aspx file, the request is processed by the page via the page handler.
The ASP.NET page handler is only one type of handler. ASP.NET comes with several other built-in handlers such as the Web service handler for .asmx files.
You can create custom HTTP handlers when you want special handling that you can identify using file name extensions in your application. For example, the following scenarios would be good uses of custom HTTP handlers:
RSS feeds To create an RSS feed for a site, you can create a handler that emits RSS-formatted XML. You can then bind the .rss extension (for example) in your application to the custom handler. When users send a request to your site that ends in .rss, ASP.NET will call your handler to process the request.
Image server If you want your Web application to serve images in a variety of sizes, you can write a custom handler to resize images and then send them back to the user as the handler's response.
HTTP handlers have access to the application context, including the requesting user's identity (if known), application state, and session information. When an HTTP handler is requested, ASP.NET calls the ProcessRequest method on the appropriate handler. The handler's ProcessRequest method creates a response, which is sent back to the requesting browser. As with any page request, the response goes through any HTTP modules that have subscribed to events that occur after the handler has run.
HttpHandler Example,
HTTP Handler in ASP.NET 2.0
A handler is responsible for fulfilling requests from a browser. Requests that a browser manages are either handled by file extension or by calling the handler directly.The low level Request and Response API to service incoming Http requests are Http Handlers in Asp.Net. All handlers implement the IHttpHandler interface, which is located in the System.Web namespace. Handlers are somewhat analogous to Internet Server Application Programming Interface (ISAPI) extensions.
You implement the IHttpHandler interface to create a synchronous handler and the IHttpAsyncHandler interface to create an asynchronous handler. The interfaces require you to implement the ProcessRequest method and the IsReusable property. The ProcessRequest method handles the actual processing for requests made, while the Boolean IsReusable property specifies whether your handler can be pooled for reuse to increase performance or whether a new handler is required for each request.
The .ashx file extension is reserved for custom handlers. If you create a custom handler with a file name extension of .ashx, it will automatically be registered within IIS and ASP.NET. If you choose to use an alternate file extension, you will have to register the extension within IIS and ASP.NET. The advantage of using an extension other than .ashx is that you can assign multiple file extensions to one handler.
Configuring HTTP Handlers
The configuration section handler is responsible for mapping incoming URLs to the IHttpHandler or IHttpHandlerFactory class. It can be declared at the computer, site, or application level. Subdirectories inherit these settings. Administrators use the tag directive to configure the section. directives are interpreted and processed in a top-down sequential order. Use the following syntax for the section handler:
Creating HTTP Handlers
To create an HTTP handler, you must implement the IHttpHandler interface. The IHttpHandler interface has one method and one property with the following signatures: void ProcessRequest(HttpContext); bool IsReusable {get;}
Any Class that implements System.Web.IHttpHandler Interface becomes HttpHandler. And this class run as processes in response to a request made to the ASP.NET Site.
The most common handler is an ASP.NET page handler that processes .aspx files. When users request an .aspx file, the request is processed by the page through the page handler(The Class that implements System.Web.IHttpHandler Interface).
You can create your own custom HTTP handlers that render custom output to the browser.
Some ASP.NET default handlers are:
An HttpHandler (or IHttpHandler) is basically anything that is responsible for serving content. An ASP.NET page (aspx) is a type of handler.
You might write your own, for example, to serve images etc from a database rather than from the web-server itself, or to write a simple POX service (rather than SOAP/WCF/etc)
Any Class that implements System.Web.IHttpHandler Interface becomes HttpHandler. And this class run as processes in response to a request made to the ASP.NET Site.
The most common handler is an ASP.NET page handler that processes .aspx files. When users request an .aspx file, the request is processed by the page through the page handler(The Class that implements System.Web.IHttpHandler Interface).
You can create your own custom HTTP handlers that render custom output to the browser.
Some ASP.NET default handlers are:
HttpHandler Example,
HTTP Handler in ASP.NET 2.0
A handler is responsible for fulfilling requests from a browser. Requests that a browser manages are either handled by file extension or by calling the handler directly.The low level Request and Response API to service incoming Http requests are Http Handlers in Asp.Net. All handlers implement the IHttpHandler interface, which is located in the System.Web namespace. Handlers are somewhat analogous to Internet Server Application Programming Interface (ISAPI) extensions.
You implement the IHttpHandler interface to create a synchronous handler and the IHttpAsyncHandler interface to create an asynchronous handler. The interfaces require you to implement the ProcessRequest method and the IsReusable property. The ProcessRequest method handles the actual processing for requests made, while the Boolean IsReusable property specifies whether your handler can be pooled for reuse to increase performance or whether a new handler is required for each request.
The .ashx file extension is reserved for custom handlers. If you create a custom handler with a file name extension of .ashx, it will automatically be registered within IIS and ASP.NET. If you choose to use an alternate file extension, you will have to register the extension within IIS and ASP.NET. The advantage of using an extension other than .ashx is that you can assign multiple file extensions to one handler.
Configuring HTTP Handlers
The configuration section handler is responsible for mapping incoming URLs to the IHttpHandler or IHttpHandlerFactory class. It can be declared at the computer, site, or application level. Subdirectories inherit these settings. Administrators use the tag directive to configure the section. directives are interpreted and processed in a top-down sequential order. Use the following syntax for the section handler:
Creating HTTP Handlers
To create an HTTP handler, you must implement the IHttpHandler interface. The IHttpHandler interface has one method and one property with the following signatures: void ProcessRequest(HttpContext); bool IsReusable {get;}
An ASP.NET HTTP handler is the process (frequently referred to as the "endpoint") that runs in response to a request made to an ASP.NET Web application. The most common handler is an ASP.NET page handler that processes .aspx files. When users request an .aspx file, the request is processed by the page via the page handler.
The ASP.NET page handler is only one type of handler. ASP.NET comes with several other built-in handlers such as the Web service handler for .asmx files.
You can create custom HTTP handlers when you want special handling that you can identify using file name extensions in your application. For example, the following scenarios would be good uses of custom HTTP handlers:
RSS feeds To create an RSS feed for a site, you can create a handler that emits RSS-formatted XML. You can then bind the .rss extension (for example) in your application to the custom handler. When users send a request to your site that ends in .rss, ASP.NET will call your handler to process the request.
Image server If you want your Web application to serve images in a variety of sizes, you can write a custom handler to resize images and then send them back to the user as the handler's response.
HTTP handlers have access to the application context, including the requesting user's identity (if known), application state, and session information. When an HTTP handler is requested, ASP.NET calls the ProcessRequest method on the appropriate handler. The handler's ProcessRequest method creates a response, which is sent back to the requesting browser. As with any page request, the response goes through any HTTP modules that have subscribed to events that occur after the handler has run.
Source: Stackoverflow.com