Pass a lambda expression in place of IComparer or IEqualityComparer or any single-method interface?

Question

I happened to have seen some code where this guy passed a lambda expression to a ArrayList.Sort(IComparer here) or a IEnumerable.SequenceEqual(IEnumerable list, IEqualityCom

Answer 1

In case if you need this function for use with lambda and possibly two different element types:

static class IEnumerableExtensions
{
    public static bool SequenceEqual(this IEnumerable first, IEnumerable second, Func comparer)
    {
        if (first == null)
            throw new NullReferenceException("first");

        if (second == null)
            throw new NullReferenceException("second");

        using (IEnumerator e1 = first.GetEnumerator())
        using (IEnumerator e2 = second.GetEnumerator())
        {
            while (e1.MoveNext())
            {
                if (!(e2.MoveNext() && comparer(e1.Current, e2.Current)))
                    return false;
            }

            if (e2.MoveNext())
                return false;
        }

        return true;
    }
}