In web.config in handlers we have the following handler configured:

<add name="SimpleHandlerFactory-Integrated" path="*.ashx" verb="GET,HEAD,POST,DEBUG" type="System.Web.UI.SimpleHandlerFactory" modules="ManagedPipelineHandler" scriptProcessor="" resourceType="Unspecified" requireAccess="Script" allowPathInfo="false" preCondition="integratedMode" responseBufferLimit="4194304" />

this handler is in web.config in the microsoft.net framework directory as well, but since <clear /> is called in the local web.config, it has to be re-added.

The problem we're experiencing is that any httphandler with a path which matches "*.ashx" is handled by simplehandlerfactory, which eventually returns a 404 instead of the actual handler. This however doesn't happen if the handler is defined before the simplehandlerfactory.

But I'm not really sure if custom handlers should be put before the simplehandlerfactory ?