Solution : Predefined type 'System.Runtime.CompilerServices.IAsyncStateMachine' is not defined or imported

Posted on 05 April 2015

Hi all,

When you try to create a simple .NET console application with a async method you might get the following error

Predefined type 'System.Runtime.CompilerServices.IAsyncStateMachine' is not defined or imported

This is because of targeting the wrong .NET framework version. For async to work out of the box you need to target your application to .NET 4.5 (at the minimum). Go ahead continue !!