Async and await in MVC 4 Controller

Question

Every time I try to use the new Async and Await operators and return a collection of objects from a database I get an Invalid Operation

Answer 1

It's been some time since this question was answered. But I was having a similar situation with MVC 5 and I was able to make a [ChildActionOnly] work asynchronously just by commenting out the following line under section of web.config file.

EDIT: Consider this a workaround while you find a real solution for your situation. Please see Leri's comments below.