C# suffix checking

    using System;
    using System.Collections.Generic;
    using System.Text;
    using System.Diagnostics;
    using System.Globalization;

    public class MyClass
    {
        private static Random random = new Random((int)DateTime.Now.Ticks);
        private static string RandomString(int size)
        {
            StringBuilder builder = new StringBuilder();
            char ch;
            for (int i = 0; i < size; i++)
            {
                ch = Convert.ToChar(Convert.ToInt32(Math.Floor(26 * random.NextDouble() + 65)));
                builder.Append(ch);
            }

            return builder.ToString();
        }


        public static void RunSnippet()
        {
            List<string> randomStrings = new List<string>();
            List<string> noSuffixList = new List<string>();
            List<string> hasSuffixList = new List<string>();

            const string SUFFIX = "12";
            const char SUFFIXCHAR1 = '1';
            const char SUFFIXCHAR2 = '2';
            const int UPPERLIMIT = 100000;
            for (int i = 0; i < UPPERLIMIT; ++i)
            {
                string randomString = RandomString(9 + random.Next(20));

                if (i % 2 == 0)
                {
                    randomString += SUFFIX;
                }

                randomStrings.Add(randomString);
            }

            Stopwatch timer;

            noSuffixList.Clear();
            hasSuffixList.Clear();
            timer = Stopwatch.StartNew();
            foreach (string randomString in randomStrings)
            {
                (randomString.Contains(SUFFIX) ? hasSuffixList : noSuffixList).Add(randomString);
            }
            timer.Stop();
            WL("Contains:  {0} ({1})", timer.Elapsed.TotalMilliseconds.ToString("0.00 ms"), hasSuffixList.Count);

            noSuffixList.Clear();
            hasSuffixList.Clear();
            timer = Stopwatch.StartNew();
            foreach (string randomString in randomStrings)
            {
                (randomString.LastIndexOf(SUFFIX) > 0 ? hasSuffixList : noSuffixList).Add(randomString);
            }
            timer.Stop();
            WL("LastIndexOf:  {0} ({1})", timer.Elapsed.TotalMilliseconds.ToString("0.00 ms"), hasSuffixList.Count);

            noSuffixList.Clear();
            hasSuffixList.Clear();
            timer = Stopwatch.StartNew();
            foreach (string randomString in randomStrings)
            {
                (randomString.EndsWith(SUFFIX, StringComparison.Ordinal) ? hasSuffixList : noSuffixList).Add(randomString);
            }
            timer.Stop();
            WL("EndsWith using StringComparison.Ordinal:  {0} ({1})", timer.Elapsed.TotalMilliseconds.ToString("0.00 ms"), hasSuffixList.Count);

            noSuffixList.Clear();
            hasSuffixList.Clear();
            timer = Stopwatch.StartNew();
            CompareInfo myComp = CultureInfo.InvariantCulture.CompareInfo;
            foreach (string randomString in randomStrings)
            {
                (myComp.IsSuffix(randomString, SUFFIX) ? hasSuffixList : noSuffixList).Add(randomString);
            }
            timer.Stop();
            WL("IsSuffix:  {0} ({1})", timer.Elapsed.TotalMilliseconds.ToString("0.00 ms"), hasSuffixList.Count);

            noSuffixList.Clear();
            hasSuffixList.Clear();
            timer = Stopwatch.StartNew();
            foreach (string randomString in randomStrings)
            {
                (randomString.Substring(randomString.Length - SUFFIX.Length).Equals(SUFFIX) ? hasSuffixList : noSuffixList).Add(randomString);
            }
            timer.Stop();
            WL("Substring compare:  {0} ({1})", timer.Elapsed.TotalMilliseconds.ToString("0.00 ms"), hasSuffixList.Count);

            noSuffixList.Clear();
            hasSuffixList.Clear();
            timer = Stopwatch.StartNew();
            foreach (string randomString in randomStrings)
            {

                (randomString[randomString.Length-1] == SUFFIXCHAR2 ? hasSuffixList : noSuffixList).Add(randomString);
            }
            timer.Stop();
            WL("Last char equality:  {0} ({1})", timer.Elapsed.TotalMilliseconds.ToString("0.00 ms"), hasSuffixList.Count);

            noSuffixList.Clear();
            hasSuffixList.Clear();
            timer = Stopwatch.StartNew();
            foreach (string randomString in randomStrings)
            {
                (randomString[randomString.Length - 1] == SUFFIXCHAR2
                    && randomString[randomString.Length - 2] == SUFFIXCHAR1
                    ? hasSuffixList : noSuffixList).Add(randomString);
            }
            timer.Stop();
            WL("Last 2 char equality:  {0} ({1})", timer.Elapsed.TotalMilliseconds.ToString("0.00 ms"), hasSuffixList.Count);

        }

        #region Helper methods

        public static void Main()
        {
            try
            {
                RunSnippet();
            }
            catch (Exception e)
            {
                string error = string.Format("---\nThe following error occurred while executing the snippet:\n{0}\n---", e.ToString());
                Console.WriteLine(error);
            }
            finally
            {
                Console.Write("Press any key to continue...");
                Console.ReadKey();
            }
        }

        private static void WL(object text, params object[] args)
        {
            Console.WriteLine(text.ToString(), args);
        }

        private static void RL()
        {
            Console.ReadLine();
        }

        private static void Break()
        {
            System.Diagnostics.Debugger.Break();
        }

        #endregion
    }