If you want to compare two sequences in .NET 3.5 and beyond (that's the version of the framework which C# 3.0 ships with), then you should use the SeqenceEqual extension method on the Enumerable class in the System.Linq namespace.
However, for this, it will use the default equality comparer for the type parameter T in the IEnumerable implementations it is comparing.
If you want to change the way that equality is checked for, then you should pass an implementation of IEqualityComparer to the SequenceEqual method to use when comparing the items from each sequence.
Also, if you are trying to see if two sets are equal (as represented by IEnumerable) then your best bet is to check use the Except extension method on the Enumerable class and make sure that the result set doesn't have any entries, and that both IEnumerable implementations have the same number of entries (since Except can return an empty sequence even with different length sequences passed to it) which you can do with the Count extension method.
