How is the order of execution for HttpModules determined?

问题

Suppose that both FirstModule and SecondModule handle the Application_BeginRequest event. Will it execute in the order defined in the web.config?

<httpModules>
  <add type="MyApp.FirstModule, MyApp" name="FirstModule"/>
  <add type="MyApp.SecondModule, MyApp" name="SecondModule"/>
  <add type="OtherApp.OtherModule, OtherApp" name="OtherModule"/>
</httpModules>

Are there other ways that the order can be specified?

回答1:

According to this forum post, HttpModules are executed in the order in which they were registered. This makes sense to me, because otherwise the <clear> and <remove> directives would also not work as expected, e.g. when used like this:

<httpModules> 
   <clear/>
   <add... />
</httpModules>

回答2:

According to the Internet Information Services (IIS) 7.0 Resource Kit book extract from Microsoft Press,

To resolve such relative ordering dependencies, the administrator can control the relative ordering of modules by changing the order in which they are listed in the modules section.

This works because the server uses the order in the modules configuration section to order module execution within each request processing stage. By placing module A before module B in the list, you can allow module A to execute before module B.

来源：https://stackoverflow.com/questions/2427451/how-is-the-order-of-execution-for-httpmodules-determined