test.cs

using System;
using System.IO;
using System.Diagnostics;
 
public class HelloWorld
{
    static public void Main ()
    {
        Console.CursorVisible = false;

        var ScreenWidth = 640;
        var ScreenHeight = 480;
        var BytesPerPixel = 2;

        var random = new Random();
        var buffer = new Byte[ScreenWidth * ScreenHeight * BytesPerPixel ];

        Stopwatch stopWatch = new Stopwatch();
        stopWatch.Start();

        for(var i = 0; i < 10; i++) {

            using (var fb = new FileStream("/dev/fb0", FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite))
            {
                random.NextBytes(buffer);
                fb.Write(buffer, 0, buffer.Length);
                fb.Close();
            }
        }

    /*

        var random = new Random();
        var buffer = new Byte[ScreenWidth * ScreenHeight * BytesPerPixel ];
        using(var mmf = MemoryMappedFile.CreateFromFile("/dev/fb0", FileMode.Open))
        using(var accessor = mmf.CreateViewAccessor())
        {
            for(var i = 0; i < 100; i++) {
                random.NextBytes(buffer);
                accessor.WriteArray(0, buffer, 0, buffer.Length);
            }
        }

    /**/

        stopWatch.Stop();
        TimeSpan ts = stopWatch.Elapsed;

        string elapsedTime = String.Format("{0:00}:{1:00}:{2:00}.{3:00}",
            ts.Hours, ts.Minutes, ts.Seconds,
            ts.Milliseconds / 10);
        Console.WriteLine("RunTime " + elapsedTime);

        Console.CursorVisible = true;
    }
}