using System;
using System.Linq;

namespace DraftApp
{
    class Program
    {
        static void Main(string[] args)
        {
            var testUrl = new[] { "http://www.beta.microsoft.com/path/page.htm", "http://test.whatever.co.uk" };

            foreach (var s in testUrl)
            {
                var result = ExampleExtractor(s);

                Console.WriteLine(result);
            }

            Console.ReadKey();
        }

        private static string ExampleExtractor(string url)
        {
            var extensions = new[] {".com", ".co.uk", ".nl", ".eu"};

            foreach (var extension in extensions)
            {
                var foundIndex = url.IndexOf(extension, StringComparison.Ordinal);

                if (foundIndex > 0)
                {
                    url = url.Substring(0, foundIndex);
                    break;
                }
            }

            var tmp = url.Split('.');

            return tmp[tmp.Count()-1];
        }
    }
}