C# extension method to partition sequences by a value

EnumerableExtensions_Partition.cs

using System;
using System.Collections.Generic;
using System.Linq;
using SharpX.Extensions;

static class EnumerableExtensions
{
    public static IEnumerable<IEnumerable<T>> Partition<T, TKey>(this IEnumerable<T> source, Func<T, TKey> selector)
    {
        var result = new List<IEnumerable<T>>();

        var ordered = source.OrderBy(selector);
        var partition = new List<T>();
        for (var i = 0; i < ordered.Count(); i++) {
            var current = ordered.ElementAt(i);
            var currentValue = selector(current);
            partition.Add(current);
            if (ordered.ElementAtOrNothing(i + 1).MatchJust(out var next)) {
                var nextValue = selector(next);
                if (currentValue.Equals(nextValue)) {
                    continue;
                }
                else {
                    result.Add(new List<T>(partition));
                    partition.Clear();
                }
            }
            else {
                result.Add(partition);
            }
        }

        return result;
    }
}