Obvious Extension Methods: The Simple Join

Maybe you just want to know the things from list1 where they have a match in list2.

You can do that yesterday and today with list1.Join(list2, item1=>item1, item2=>item2, (item1,item2)=>item1);

But today and tomorrow, you can simply do list1.Join(list2).

Obvious, right?

37. public static class Extensions
38. {
39.     public static IEnumerable<T> Join<T>(this IEnumerable<T> outer,
40.         IEnumerable<T> inner)
41.     {
42.         return outer.Join(inner, a => a, b => b, (a, b) => a);
43.     }
44. }