Find an Available Port with C#

AvailablePorts.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net.NetworkInformation;
using System.Net;

namespace AvailablePort
{
    class Program
    {
        static void Main(string[] args)
        {

            Console.WriteLine(GetAvailablePort(1000).ToString());
            Console.ReadLine();
        }

        /// <summary>
        /// checks for used ports and retrieves the first free port
        /// </summary>
        /// <returns>the free port or 0 if it did not find a free port</returns>
        public static int GetAvailablePort(int startingPort)
        {
            IPEndPoint[] endPoints;
            List<int> portArray = new List<int>();

            IPGlobalProperties properties = IPGlobalProperties.GetIPGlobalProperties();

            //getting active connections
            TcpConnectionInformation[] connections = properties.GetActiveTcpConnections();
            portArray.AddRange(from n in connections
                               where n.LocalEndPoint.Port >= startingPort
                               select n.LocalEndPoint.Port);

            //getting active tcp listners - WCF service listening in tcp
            endPoints = properties.GetActiveTcpListeners();
            portArray.AddRange(from n in endPoints
                               where n.Port >= startingPort
                               select n.Port);

            //getting active udp listeners
            endPoints = properties.GetActiveUdpListeners();
            portArray.AddRange(from n in endPoints
                               where n.Port >= startingPort
                               select n.Port);

            portArray.Sort();

            for (int i = startingPort; i < UInt16.MaxValue; i++)
                if (!portArray.Contains(i))
                    return i;

            return 0;
        }
    }
}