Represent 4 byte int in byte array in c and c#

bitwiseop.c

unsigned long n = 12121212;
unsigned long len = 0;
char msg[5];

msg[0] = (n >> 24) & 0xFF;
msg[1] = (n >> 16) & 0xFF;
msg[2] = (n >> 8) & 0xFF;
msg[3] = n & 0xFF;
msg[4] = 0;

for (int i = 0; i < 4; i++)
{
	len <<= 8;
	len |= (unsigned char)msg[i];
}

if (n != len)
{
	printf("NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO\n");
}
else
{
	printf("ok\n");
}

  /////////////////////////////
  // or in c#
  /////////////////////////////
  
  int len = 12121212;
  byte[] msg = new byte[4 + 1 + len];
  int k = 0;

  msg[k++] = (byte)((len >> 24) & 0xFF);
  msg[k++] = (byte)((len >> 16) & 0xFF);
  msg[k++] = (byte)((len >> 8) & 0xFF);
  msg[k++] = (byte)(len & 0xFF);
  
  int len2 = 0;
  for (int i = 0; i < 4; i++)
  {
      len2 <<= 8;
      len2 |= msg[i];
  }