In other words: an interface with one member is equivalent to a function reference. There is an equivalence between public interface IThingDoer { int DoTheThin

In other words: an interface with one member is equivalent to a function reference. There is an equivalence between public interface IThingDoer { int DoTheThing(int value); } and Func<int, int> doTheThing. Converting from one to the other is left as an exercise to the reader.