If the action returns an HttpResponseMessage, Web API converts the return value directly into an HTTP response message, using the properties of the HttpResponseMessage object to populate the response. This option gives you a lot of control over the response message. For example, the following controller action sets the Cache-Control header.
The Macchiato Defined. The macchiato (mah-key-AH-toe) is a cornerstone of Italian coffee culture, along with the espresso and cappuccino, among other coffee drinks. It's basically an espresso (served in a demitasse cup) with a small amount of foamed milk on top -- the name macchiato means marked.
Americans invented something called a latte macchiato, which means milk marked with espresso. It is essentially a latte, but the milk is put in the cup first and then the shots of espresso last. This is what has become the caramel macchiato.