LambdaComparer.cs

/// <summary>
    /// Useful for comparing two objects.
    /// Example usage:
    ///    var dropOffComparer = new LambdaComparer<ConsolidationDropOff>((x, y) => x.Id == y.Id);
    ///    dropOffs.Contains(dropOff, dropOffComparer);
    /// </summary>
    /// <typeparam name="T"></typeparam>
    public class LambdaComparer<T> : IEqualityComparer<T>
    {
        Func<T, T, bool> _comparer;
        Func<T, int> _hash;

        public LambdaComparer(Func<T, T, bool> comparer)
        {
            _comparer = comparer;
            _hash = t => t.GetHashCode();
        }
        public LambdaComparer(Func<T, T, bool> comparer, Func<T, int> hash)
        {
            _comparer = comparer;
            _hash = hash;
        }

        public bool Equals(T x, T y)
        {
            return _comparer(x, y);
        }
        public int GetHashCode(T obj)
        {
            return _hash(obj);
        }
    }

    public static class SequenceExtensions
    {
        public static bool SequenceEqual<T>(this IEnumerable<T> first, IEnumerable<T> second, Func<T, T, bool> comparer)
        {
            return first.SequenceEqual(second, new LambdaComparer<T>(comparer));
        }
        public static bool SequenceEqual<T>(this IEnumerable<T> first, IEnumerable<T> second, Func<T, T, bool> comparer, Func<T, int> hash)
        {
            return first.SequenceEqual(second, new LambdaComparer<T>(comparer, hash));
        }
    }