MergeSort and LINQ

Here is an implementation of the merge sort algorithm, which operates on a sequence/list of items:

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;

namespace MergeSort
{
    public static class MergeSort_Extensions
    {
        public static IEnumerable<T> MergeSort<T>(this IList<T> items, Comparison<T> comparison)
        {
            return MergeSortInternal<T>(items, items.Count, comparison);
        }

        public static IEnumerable<T> MergeSort<T>(this IEnumerable<T> items, Comparison<T> comparison)
        {
            return MergeSortInternal<T>(items, items.Count(), comparison);
        }

        private static IEnumerable<T> MergeSortInternal<T>(IEnumerable<T> items, int count, Comparison<T> comparison)
        {
            Debug.Assert(items != null);
            Debug.Assert(comparison != null);

            if (count == 0)
                yield break;

            if (count == 1)
            {
                yield return items.First();
                yield break;
            }

            // sort both halves recursively
            IEnumerator<T> enumA = MergeSortInternal<T>(items.Take<T>(count / 2), count / 2, comparison).GetEnumerator();
            IEnumerator<T> enumB = MergeSortInternal<T>(items.Skip<T>(count / 2), count - count / 2, comparison).GetEnumerator();

            bool movedA = enumA.MoveNext();
            bool movedB = enumB.MoveNext();
            Debug.Assert(movedA && movedB);

            // merge
            while (true)
            {
                if (comparison(enumA.Current, enumB.Current) > 0)
                {
                    // swap enumerators
                    IEnumerator<T> iterTemp = enumA;
                    enumA = enumB;
                    enumB = iterTemp;
                }

                yield return enumA.Current;
                if (enumA.MoveNext() == false)
                {
                    // return the remaining items
                    do yield return enumB.Current;
                    while (enumB.MoveNext());
                    break;
                }
            }
        }
    }
}

P.S. The code was formatted with http://formatmysourcecode.blogspot.com/