Fast IEnumerable<enum1> to List<enum2> convertation

Question

I have two same enums that have the same names of members, but they are in different namespaces so they are "different types", but in fact namespace1.enum1 {a,b,c,d,e,f} and namespace2.enum2 {a,b,c,d,e,f}

How is the easiest way to convert IEnumerable<enum1> to List<enum2> without using loops?

Answer 1

Well something's going to loop somewhere, but it doesn't have to be in your code. Just a LINQ Select will be fine:

var result = original.Select(x => (Enum2) x).ToList();

Answer 2

Or you can use Cast (still O(n) :-))

var result = original.Cast<int>().Cast<Enum2>().ToList();

Warning It seems that this will not always work as expected (InvalidCastException can be thrown in some cases). See comments to figure out why.