How to assert an IEnumerable parameter where order is unimportant?

I'm writing a unit test, I want to ensure that a particular method is called with some parameters: ``` var myMock = MockRepository.GenerateMock<IMyService>(); ``` IMyService has a method on it with the signature ``` public bool SomeMethod(IEnumerable<string> values) ``` I have a business logic layer which consumes my mock ``` public class BusinessLogic { protected MyMock MyMock{get;set;} public BusinessLogic (myMock) { this.MyMock = myMock; } public bool DoLogic() { var myCollection = // loaded from somewhere return this.MyMock(myCollection); } } ``` I want to test the DoLogic method by making sure that it calls SomeMethod properly. However I have no control (and don't really want it over the ordering of the collection). I want to assert that the method `SomeMethod` is called with the IEnumerable `{"a", "b", "c"}` but I don't care on the order. So far I have ``` myMock.Expect(x => x.MyMethod(new string[]{"a", "b", "c"}); ``` and ``` myMock.AssertWasCalled(x => x.MyMethod(new string[]{"a", "b", "c"}); ``` But this will fail if it's called with `{"b", "a", "c"}`. I don't want to change my business logic to ensure the ordering of the parameters (as this would design the BLL around the tests). How can I assert this method call?