Can you create a simple 'EqualityComparer' using a lambda expression

Question

Short question:

Is there a simple way in LINQ to objects to get a distinct list of objects from a list based on a key property on the objects.

Answer 1

Building on Charlie Flowers' answer, you can create your own extension method to do what you want which internally uses grouping:

    public static IEnumerable Distinct(
        this IEnumerable seq, Func getKey)
    {
        return
            from item in seq
            group item by getKey(item) into gp
            select gp.First();
    }

You could also create a generic class deriving from EqualityComparer, but it sounds like you'd like to avoid this:

    public class KeyEqualityComparer : IEqualityComparer
    {
        private Func GetKey { get; set; }

        public KeyEqualityComparer(Func getKey) {
            GetKey = getKey;
        }

        public bool Equals(T x, T y)
        {
            return GetKey(x).Equals(GetKey(y));
        }

        public int GetHashCode(T obj)
        {
            return GetKey(obj).GetHashCode();
        }
    }