using System;

​

public class Program

{

    public static void Main()

    {

        foreach (var number in new int[] { byte.MaxValue, short.MaxValue, 0xFFFFFF, int.MaxValue})

            Console.WriteLine("{0} byte(s) in {1}", GetBytes(number).Length, number);

    }

​

    public static byte[] GetBytes(int number)

    {

        byte[] bytes;

        if (number <= 0xFF)

        {

            bytes = new byte[] { (byte)number };

        }

        else if (number <= 0xFFFF)

        {

            bytes = BitConverter.GetBytes((short)number);

        }

        else if (number <= 0xFFFFFF)

        {

            bytes = new byte[3];

            var tmp = BitConverter.GetBytes(number);

            Array.Copy(tmp, bytes, 3);

        }

        else

        {

            bytes = BitConverter.GetBytes(number);

        }

​

        return bytes;

    }

}