C#

private void Save(Stream s)
{
  FileStream file = new FileStream("c:\temp\file.txt", ...);
  using (file)
  {
    byte[] buffer = new byte[4096];
    int read = 0;
    read = s.Read(buffer, 0, buffer.Length);
    while (read != 0)
    {
      file.Write(buffer, 0, read);
      read = s.Read(buffer, 0, buffer.Length);
    }
  }
}

public override in Create(object obj)
{
  Bid bid = obj as Big;
  if (bid == null) throw new ArgumentException("Must pass a Bid object.",
    "obj");
  // Continue with bid...
}