program.cs

using System.IO;

namespace binarywritertest
{
    class Program
    {
        static void Main(string[] args)
        {
            byte[] data = new byte[100];
            for (byte i = 0; i < 100; i++)
            {
                data[i] = (byte)(i+100);
            }

            File.WriteAllBytes(@"c:\temp\array-writeall.dat", data);
            using (BinaryWriter bw = new BinaryWriter(File.Open(@"c:\temp\array-binarywriter.dat", FileMode.OpenOrCreate)))
            {
                bw.Write(data);
            }

            using (FileStream fileStream = new FileStream(@"c:\temp\array-filestream.dat", FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite))
            {
                fileStream.Write(data, 0, 100);
            }
        }
    }
}