hickford

public static class LINQExtensions
{
    public static IEnumerable<IGrouping<TKey, TElement>> GroupAdjacentBy<TElement, TKey>(this IEnumerable<TElement> source, Func<TElement, TKey> keySelector, IEqualityComparer<TKey> comparer=null)
    {
        comparer = comparer ?? EqualityComparer<TKey>.Default;
        List<TElement> elements = null;
        TKey key = default(TKey);
        TKey lastKey = default(TKey);
        foreach (var x in source)
        {