stream.cs

    class Program
    {
        static void Main(string[] args)
        {
            using (var fileStream = new FileStream(@"c:\temp\test.txt", FileMode.Open))
            using (var memoryStream = new MemoryStream())
            {
                fileStream.CopyTo(memoryStream);
                byte[] data = memoryStream.ToArray();

                Console.WriteLine("Read " + data.Length + " bytes");
            }
        }

    }