Written by SoundararajanApril 5, 2015July 8, 2016 Solution : Predefined type ‘System.Runtime.CompilerServices.IAsyncStateMachine’ is not defined or imported Moved here : http://soundararajan.in/blog/2015/04/05/solution-predefined-type-system-runtime-compilerservices-iasyncstatemachine-is-not-defined-or-imported/ Advertisements EmailLike this:Like Loading... Related 2 thoughts on “Solution : Predefined type ‘System.Runtime.CompilerServices.IAsyncStateMachine’ is not defined or imported” This is not a solution. It’s only a workaround. What if I am not allowed to move to .Net 4.5? Reply NO, this is not a workaround. To use async feature you atleast need .NET 4.5. If you are not allowed to move to 4.5, i guess you can’t use async. There is of course CTP builds (again it’s .NET 4.5 , or possibly patches to 4.0) that use to work with VS 2010, but not anymore. You probably should here this from Jon Skeet Reply Leave a Reply Cancel reply Enter your comment here... Please log in using one of these methods to post your comment: Email (Address never made public) Name Website You are commenting using your WordPress.com account. ( Log Out / Change ) You are commenting using your Google+ account. ( Log Out / Change ) You are commenting using your Twitter account. ( Log Out / Change ) You are commenting using your Facebook account. ( Log Out / Change ) w Cancel Connecting to %s Notify me of new comments via email. Notify me of new posts via email.