Task<TResult>

any value type

any reference type

void

Task

Without an await expression or statement a method with async modifier will execute synchronously.

An async method runs asynchronously until it reaches its first await expression

If the method with async modifier doesn't contain an await expression or statement the compiler will generate a compilation error.

The caller of a void-returning async method can't await it

async method can declare in, ref and out parameters

With any type

Only in async context

With Task

With Task<T>

In catch or finally blocks

With any lambdas and anonymous methods which return Task

With any method which returns Task

With a method which has await in its body

With classes

With any methods