为什么在我的项目中不能等待Task ？

I have a project that is targeting the .NET 4 framework and I've created a method which updates data in a database. The method itself also uses a flag (runAsync) to determine whether it should run asynchronously or not. I'm getting an error that 'System.Threading.Tasks.Task< HttpResponseMessage > is not awaitable' but I am using this same code in another application and it works fine. What am I doing wrong, or what am I missing to get this to work?I have a project that is targeting the .NET 4 f