HTTP Handler

Have you ever thought what happens when a request comes to IIS. Sending a request and serving the request with a response actually has lot of activities involved.

Infact the way request is processed is different for IIS versions also.
In IIS 5.0 and IIS 6.0 there are two seperate pipelines involved.
While in the case of IIS7.0 you have an option of choosing whether two pipelines are required or you want only one integrated pipeline to do the work.

Lets first examine How it works in IIS5.0 and IIS6.0
Inside the IIS, ISAPI(Internet Server Application Programming Interface) extensions are implemented.So when the request comes the IIS determines which ISAPI extension can process the request based on the file name extension.
e.g. If the request is for AspNetLovers.aspx then ASP.Net will handle the request because ASP.Net is the ISAPI Extension for aspx pages. There are others which are also mapped to ASP.Net extension e.g. request for .ascx, .ashx, and .asmx files.This means that the request for static pages e.g. .html files will not be able to take advantage to ASP.Net ISAPI Extension. We also understand this as ASP.Net has handlers for .aspx,.ascx,.ashx and .asmx files. In case of other types of files since there is no extension we need to create one. This doesn't mean that .htm file will not be rendered when hosted inside IIS. They will be rendered as they are static contents but they can't take advantage of ASP.Net ISAPI extension features.The reason is:If IIS doesn't find the appropriate handler default StaticFileHandler tries to process the request.

Thus we got to know why we need handler. As described above requests which cannot be handled by ASPNet ISAPI extension needs to be handled via creating our own custom handler and registering the handler in webconfig file and IIS.

Enough with the discussion part let's do some practical for it.
We are building an application where if the user requests the file which cannot be handled even by the default handler then an error message is displayed.
namespace DemoForHTTPHandlerAndHTTPModule
{
    public class CustomHandler:IHttpHandler
    {
        public bool IsReusable
        {
            get { return false; }
        }

        public void ProcessRequest(HttpContext context)
        {
            if (!(context.Request.Url.AbsolutePath.EndsWith(".aspx")))
            {
                context.Response.Write("Error..Please type a valid aspx page");
            }
        }
    }
}
 Registering of Handler in web.config For Integrated Pipeline:

<configuration>
  <system.webServer>
    <handlers>
      <!--<add verb="*" path="*.cspx" type="DemoHttpHandlersAndModules.CspxHandler" name="MyHandler"/>-->
    <add verb="*" path="*.cspx" type="DemoForHTTPHandlerAndHTTPModule.CustomHandler" name="CustomHandler"/>
    </handlers>
  </system.webServer>
    <system.web>
      <compilation debug="true" targetFramework="4.0" />
    </system.web>
</configuration>

Add a webform in the solution say:FrmTestHandler.aspx
Now run the solution setting FrmTestHandler.aspx as the start page.

Fig 1.1 FrmTestHandler.aspx

Now Change the extension to cspx and hit enter

Fig 1.2 Change of extension of aspx Page

 I hope you have enjoyed learning the concept. Any suggestions or complaints regarding this written blog are most welcome.

Enjoy sharing the knowledge.

 






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