BinaryReader.cs

        public static IEnumerable<byte[]> LazyReadBinaryFile(string fileName, int recordLen)
        {
            byte[] buffer = new byte[recordLen];

            using (var stream = File.OpenRead(fileName))
            {
                long remaining = stream.Length;
                int read = 0;
                while (remaining > 0)
                {
                    int c = stream.Read(buffer, read, recordLen - read);
                    remaining -= c;
                    read += c;
                    if (read == recordLen)
                    {
                        read = 0;
                        byte[] rtn = new byte[recordLen];
                        Buffer.BlockCopy(buffer, 0, rtn, 0, recordLen);
                        yield return rtn;
                    }
                }
            }
        }