using System;

using System.IO;

using System.Diagnostics;

public class Program

{

    public static void Main()

    {

        var rng = new Random();

        var bytes = new byte[0x1000000];

        rng.NextBytes(bytes);

​

        var source = new MemoryStream();

        source.Write(bytes, 0, bytes.Length);

        var sw = new Stopwatch();

        sw.Start();

        source.Position = 0;

        var dest = new MemoryStream();

        source.CopyTo(dest);

        sw.Stop();

        Console.Write($"{(float)sw.ElapsedTicks / Stopwatch.Frequency * 1000:#,0.00}ms");

    }

}