x>         public void WriteTransformation(ref byte[] buffer, ref int dataLength, WriteByteHandler handler)
x>         {
x>             if (buffer == null) return;
x>             if (dataLength < 0) return;
x>             if (handler == null) return;

x>             if (dataLength < buffer.Length)
x>             {
x>                 for (int i = dataLength; i > 0; i--)
x>                 {
x>                     buffer[i] = buffer[i - 1];
x>                 }
x>                 buffer[0] = PREFIX;
x>             }
x>             if (dataLength >= buffer.Length)
x>             {
x>                 byte[] newArray = new byte[dataLength + 1];
x>                 for (int i = 0; i < buffer.Length; i++)
x>                 {
x>                     newArray[i + 1] = buffer[i];
x>                 }
x>                 newArray[0] = PREFIX;
x>                 buffer = newArray;
x>             }
x>             dataLength++;
x>         }
x>

if (dataLength < buffer.Length)
  {
     ...
  }
  if (dataLength >= buffer.Length)

if (dataLength < buffer.Length)
  {
     ...
  }
else

x> for (int i = 0; i < buffer.Length; i++)
x> {
x>     newArray[i + 1] = buffer[i];
x> }
x>

x> Array.Copy(buffer, 0, newArray, 1, buffer.Length);
x>

public void WriteTransformation(ref byte[] buffer, ref int dataLength, WriteByteHandler writeByteHandler)
{
  if (writeByteHandler == null)
    return;
  if (dataLength < 0)
    throw new ArgumentOutOfRangeException("Data length should be non-negative", dataLength, "dataLength");
  if (buffer == null)
    buffer = new byte[0];
  if (dataLength > buffer.Length)
    throw new ArgumentOutOfRangeException("Data length should not exceed the buffer length", dataLength, "dataLength");

  var newBuffer = new byte[dataLength+1];

  newBuffer[0] = PREFIX;
  Array.Copy(buffer, 0, newBuffer, 1, dataLength);
  buffer = newBuffer;
  dataLength++;
}

if (newBuffer != null) if (buffer != null)

           (No new) Repeats 500000 buffer size 256 time 00:00:00.5496574
         (With new) Repeats 500000 buffer size 256 time 00:00:00.4979645
         * 
         * (No new) Repeats 500000 buffer size 512 time 00:00:01.0589830
         (With new) Repeats 500000 buffer size 512 time 00:00:00.9412769
         * 
         * (No new) Repeats 500000 buffer size 1024 time 00:00:02.1139021
         (With new) Repeats 500000 buffer size 1024 time 00:00:01.8606506
         * 
         * (No new) Repeats 100000 buffer size 4096 time 00:00:01.7431369
         (With new) Repeats 100000 buffer size 4096 time 00:00:01.5042657
         * 
         * (No new) Repeats 100000 buffer size 8192 time 00:00:03.3840202
         (With new) Repeats 100000 buffer size 8192 time 00:00:02.9811746

        public static void InitBuffer(byte[] buffer)
        {
            for (int i = 0; i < buffer.Length; i++)
            {
                buffer[i] = 0x55;
            }
        }

        private static void TestNoNew(int BufferLength, int RepeatCount)
        {
            byte[] buffer;
            Stopwatch timer = new Stopwatch();
            timer.Start();
            buffer = new byte[BufferLength];
            for (int i = 0; i < RepeatCount; i++)
            {
                InitBuffer(buffer);
            }

            timer.Stop();
            Console.WriteLine("(No new) Repeats {0} buffer size {1} time {2}", RepeatCount, BufferLength, timer.Elapsed);
        }

        private static void TestWithNew(int BufferLength, int RepeatCount)
        {
            byte[] buffer;
            Stopwatch timer = new Stopwatch();
            timer.Start();
            for (int i = 0; i < RepeatCount; i++)
            {
                buffer = new byte[BufferLength];
                InitBuffer(buffer);
            }

            timer.Stop();
            Console.WriteLine("(With new) Repeats {0} buffer size {1} time {2}", RepeatCount, BufferLength, timer.Elapsed);
        }

if (newBuffer != null) if (buffer != null)

S> AN>Уже только эту строку можно занести в шедевры "как не надо"

S> AN>Если предоставите линейку напрокат

S> AN>Добавка байт была не починкой, а заданием класса/функции. Приведенный код возник когда выяснилось, что посылка вначале заголовка, а потом основного сообщения приводит к ошибкам на некоторых конфигурациях. Исправлять пришлось тому кто это нашел

S> Мерили в релизе или в дебаге?

  (No new) Repeats 100000 buffer size 8192 time 00:00:02.7632629
(With new) Repeats 100000 buffer size 8192 time 00:00:02.9427531