Quick Sort in C#

Qsort.cs

using System;
using System.Collections.Generic;

namespace ConsoleApplication14
{
    class Program
    {
        static void Main(string[] args)
        {
            var A = new int[] { 4, 3, 5, 2 };
            var sorter = new QSort<int>(A);
            sorter.Sort();
            foreach (var i in sorter.A)
                Console.WriteLine(i);
            Console.Read();
        }
    }

    class QSort<T> where T:IComparable
    {
        public IList<T> A;
        public QSort(IList<T> A)
        {
            this.A = A;
        }
        public int Partition(int L, int U)
        {
            int s = U;
            int p = L;
            while (s != p)
            {
                if (A[p].CompareTo(A[s]) <= 0)
                {
                    p++;
                }
                else
                {
                    Swap(p, s);
                    Swap(p, s - 1);
                    s--;
                }
            }
            return p;
        }

        private void Swap(int p, int s)
        {
            T tmp = A[p];
            A[p] = A[s];
            A[s] = tmp;
        }

        public void Sort(int L, int U)
        {
            if (L >= U) return;
            int p = Partition(L, U);
            Sort(L, p-1);
            Sort(p+1, U);
        }

        public void Sort()
        {
            Sort(0, A.Count - 1);
        }
    }
}