memcpy, you do it wrong

gistfile1.cs

byte[] cmd = { 0x0F, 0xB1 };
byte [] luas = Encoding.ASCII.GetBytes(luaTextBox.Text);
int newSize = cmd.Length + luas.Length;
using (var ms = new MemoryStream(new byte[newSize], 0, newSize, true, true)) {
    ms.Write(cmd, 0, cmd.Length);
    ms.Write(luas, 0, luas.Length);
    byte[] merged = ms.GetBuffer();
    Core.ncon.Send(merged);
    }
  }