BitConverter.GetBytes in place

Question

I need to get values in UInt16 and UInt64 as Byte[]. At the moment I am using BitConverter.GetBytes, but this method give

Answer 1

You say you want to avoid creating new arrays and you cannot use unsafe. Either use Ulugbek Umirov's answer with cached arrays (be careful with threading issues) or:

static void ToBytes(ulong value, byte[] array, int offset) {
 unchecked {
  array[offset + 0] = (byte)(value >> (8*7));
  array[offset + 1] = (byte)(value >> (8*6));
  array[offset + 2] = (byte)(value >> (8*5));
  array[offset + 3] = (byte)(value >> (8*4));
  //...
 }
}