The awaitable and awaiter In C# 5.0 Asynchronous

Question

Task or Task object is awaitable, so we can use await key on those whose return value is Task or Task. Task or Task are the most fr

Answer 1

It is best answered in Lucian Wischik's blog post Why must async methods return Task?

In summary (and I am not doing the blog post justice, you should read it), the issue is that Task already exists, so introducing an interface would mean

• All the internal methods would need to be changed to the interface, a break change and thus almost impossible for the framework people to willingly do.
• As a programmer you would constantly need to decide if you want to return Task or the interface, a decision that doesn't matter much.
• The compiler would always need a concrete type, so even if you returned an interface from a method then it would still be compiled as Task.

The impact from the above is so massive that it doesn't make sense to provide an interface.