That is true for the `HttpRequest`, but the _Request_ property here is not of type `HttpRequest` but of type `HttpRequestBase` and it is retrieved from a _Context_ property that is of type `HttpContextBase`, so there is no guarantee that you might end up with a real `HttpRequest` that returns a non null value for the _Headers_ property.

Maybe the null check has been added somewhere in the past for a reason we are not aware of, so I'm a bit reluctant to remove it back again, you never know and it won't hurt adding it to the `IsRequestedWithXmlHttpRequest` method, and as a side effect we have a possible null value for QueryString covered as well ;-)