A small example in C# that uses the .NET framework class library. Now that IP addresses are not restricted IPv4 any more (which used to be 4 bytes that would fit in a long), but also can be IPv6 (which are 8 groups of 2 bytes totalling 16 bytes – coincidence or not the same size of a GUID), it is not a good idea to use the Address property of an…

ObsoleteConsoleApplication.cs

using System;
using System.Linq;
using System.Net;
using System.Net.Sockets;

namespace ObsoleteConsoleApplication
{
    class Program
    {
        private static IPAddress GetLocalIPAddress()
        {
            if (!System.Net.NetworkInformation.NetworkInterface.GetIsNetworkAvailable())
            {
                return null;
            }

            IPHostEntry host = Dns.GetHostEntry(Dns.GetHostName());

            return host
                .AddressList
                .FirstOrDefault(ip => ip.AddressFamily == AddressFamily.InterNetwork);
        }
        
        static void Main(string[] args)
        {
            IPAddress localIpAddress = GetLocalIPAddress();
            long ipv4 = localIpAddress.Address; // Warning	1	'System.Net.IPAddress.Address' is obsolete: 'This property has been deprecated. It is address family dependent. Please use IPAddress.Equals method to perform comparisons. http://go.microsoft.com/fwlink/?linkid=14202'

            Console.WriteLine("ipv4={0}", ipv4);
            Console.WriteLine("local IP address '{0}'", localIpAddress);
        }

        /* from the FCL source:
         * 
        [Obsolete("This property has been deprecated. It is address family dependent. Please use IPAddress.Equals method to perform comparisons. http://go.microsoft.com/fwlink/?linkid=14202")]
        public long Address { get; set; } 
         */
    }
}