QuickSort Generic

public static void QuickSortClassic<T>(IList<T> collection, int startIndex, int endIndex) where T : IComparable
        {
            if (startIndex >= endIndex)
            {
                return;
            }
            int pivotIndex = Partition(collection, startIndex, endIndex);

            QuickSortClassic(collection, startIndex, pivotIndex - 1);
            QuickSortClassic(collection, pivotIndex + 1, endIndex);

        }

        public static int Partition<T>(IList<T> collection, int startIndex, int endIndex) where T : IComparable
        {
            int pivotIndex = startIndex;
            var pivotValue = collection[endIndex];

            for (int i = startIndex; i < endIndex; i++)
            {
                if (collection[i].CompareTo(pivotValue) == -1 || collection[i].CompareTo(pivotValue) == 0)
                {
                    Swap(collection, i, pivotIndex);
                    pivotIndex++;
                }
            }
            Swap(collection, pivotIndex, endIndex);

            return pivotIndex;

        }