Performance of reading AppSetting via different backing methods

PerfTestCaseBackingMethods.cs

using System;
using System.Diagnostics;

namespace PerfBackingFields
{
    class Program
    {
        private const int Iterations = 100000;

        static void Main(string[] args)
        {
            Stopwatch timer = new Stopwatch();
            var testClass = new TestClass();

            //
            // Static backing field via read only property
            //

            Console.WriteLine("Static backing field via read only property:");

            timer.Start();
            for (var i = 0; i < Iterations; i++)
            {
                var s = testClass.ConfigValue1;
            }
            timer.Stop();

            Console.WriteLine("\tElapsed: " + timer.Elapsed.ToString());

            //
            // Read only property
            //

            Console.WriteLine("Read only property:");

            timer.Restart();
            for (var i = 0; i < Iterations; i++)
            {
                var s = testClass.ConfigValue1_RO;
            }
            timer.Stop();

            Console.WriteLine("\tElapsed: " + timer.Elapsed.ToString());

            //
            // Static read only property
            //

            Console.WriteLine("Static read only property:");

            timer.Restart();
            for (var i = 0; i < Iterations; i++)
            {
                var s = TestClass.ConfigValue1_ROS;
            }
            timer.Stop();

            Console.WriteLine("\tElapsed: " + timer.Elapsed.ToString());

            //
            // Static readonly field
            //

            Console.WriteLine("Static readonly field:");

            timer.Restart();
            for (var i = 0; i < Iterations; i++)
            {
                var s = TestClass.ConfigValue1_Static;
            }
            timer.Stop();

            Console.WriteLine("\tElapsed: " + timer.Elapsed.ToString());

            Console.ReadKey();
        }
    }

    class TestClass
    {
        private static string _configValue1;
        public string ConfigValue1
        {
            get
            {
                if (string.IsNullOrEmpty(_configValue1))
                    _configValue1 = System.Configuration.ConfigurationManager.AppSettings["ConfigValue1"];

                return _configValue1;
            }
        }

        public string ConfigValue1_RO
        {
            get
            {
                return System.Configuration.ConfigurationManager.AppSettings["ConfigValue1"];
            }
        }

        public static string ConfigValue1_ROS
        {
            get
            {
                return System.Configuration.ConfigurationManager.AppSettings["ConfigValue1"];
            }
        }

        public static readonly string ConfigValue1_Static =  System.Configuration.ConfigurationManager.AppSettings["ConfigValue1"];
    }
}