File Stream C#

using System;
using System.IO;
class TestRW 
{
  public static void Main(String[] args)
  { 
        MemoryStream destination = new MemoryStream();
        
        using (FileStream source = File.Open(@"c:\temp\data.dat",FileMode.Open))
        {
        
            Console.WriteLine("Source length: {0}", source.Length.ToString());
        
            source.CopyTo(destination);
        }
        
        Console.WriteLine("Destination length: {0}", destination.Length.ToString());
   }
}