ASP.NET httpHandlers & handlers

Question

I am confused about httpHandlers in system.web and handlers in system.webServer. What is the difference between these two configuration? And how and when to use them?

Actually another question is for modules as well: httpModules in system.web and modules in system.webServer

Answer 1

The system.webServer section in the Web.config file specifies settings for IIS 7.0 that are applied to the Web application. The system.WebServer is a child of the configuration section. For more information, see IIS 7.0: system.webServer Section Group (IIS Settings Schema).

and <system.web> specifies the root element for the ASP.NET configuration section and contains configuration elements that configure ASP.NET Web applications and control how the applications behave. httpHandlers & handlers are same.

To register an HTTP handler for IIS 6.0 use should:

<configuration>
  <system.web>
    <httpHandlers>
      <add verb="*" path="SampleHandler.new" 
        type="SampleHandler, SampleHandlerAssembly" />
    </httpHandlers>
  </system.web>
</configuration>

To register an HTTP handler for IIS 7.0 use should:

<configuration>
  <system.web>
    <httpHandlers>
      <add verb="*" path="SampleHandler.new" 
        type="SampleHandler, SampleHandlerAssembly" />
    </httpHandlers>
  </system.web>
  <system.webServer>
    <add name=SampleHandler" verb="*" path="SampleHandler.new" 
      Modules="IsapiModule" 
      scriptProcessor="FrameworkPath\aspnet_isapi.dll"
      resourceType="File" />
  </system.webServer>
</configuration>

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Answer 2

<system.web> is the configuration section for asp.net, traditionally this is where you would define your httpHandlers and httpModules.

With the introduction of IIS 7 (2007) the web server and asp.net got much more integrated and a completely new IIS configuration system was introduced.

As part of this the location for handler and module definitions was moved to <system.webServer>

If you are still using IIS6 (stop it) or use classic pipeline mode in IIS7+ you need to have your definitions under <system.web>, if you are using integrated pipeline mode in IIS7+ put them under <system.webServer>. You should not have them in both sections.