StringBuilderPerf.cs

using System;
using System.Diagnostics;
using System.Text;

namespace ConsoleApp2
{
    public class Program
    {
        public static void Main(string[] args)
        {
            Profile("Ctor() perf", 10000000, () =>
            {
                var a = new StringBuilder();
            });

            Profile("Ctor(int) perf", 10000000, () =>
            {
                var a = new StringBuilder(16);
            });

            var sb = new StringBuilder();
            sb.Append("abcdef");

            Profile("ToString perf", 10000000, () =>
            {
                sb.ToString();
            });
        }

        static void Profile(string description, int iterations, Action func)
        {
            // warm up 
            func();
            // clean up
            GC.Collect();
            GC.WaitForPendingFinalizers();
            GC.Collect();

            var watch = new Stopwatch();
            watch.Start();
            for (int i = 0; i < iterations; i++)
            {
                func();
            }
            watch.Stop();
            Console.Write(description);
            Console.WriteLine(" Time Elapsed {0} ms", watch.ElapsedMilliseconds);
        }
    }
}