HttpHandler registration on XSP4 vs IIS

The problem

You're developing an ASP.NET HttpHandler on Mono using XSP and now you need to deploy your app on IIS. What worked on XSP4 isn't working anymore and strange errors appear.

Let's start with the config that works on XSP4

<?xml version="1.0"?>
<configuration>
  <system.web>
    <httpHandlers>
      <add verb="*" path="*" type="MyHandler" />
    </httpHandlers>
  </system.web>
</configuration>

But you put that same Web.config file on IIS it throws errors.

The solution

As you see the registration happens inside system.web/httpHandlers section. That works on XSP4 and older ASP.NET but it's not the case on modern IIS. In there you need to switch to system.webServer/handlers section like this:

<?xml version="1.0"?>

<configuration>
  <system.webServer>
    <handlers>
      <add name="name" verb="*" path="*" type="MyHandler" />
    </handlers>
  </system.webServer>
</configuration>

That's it! Happy coding!