public Guid(byte[] b)
{
if (b==null)
throw new ArgumentNullException("b");
if (b.Length != 16)
throw new ArgumentException(
                   Environment.GetResourceString("Arg_GuidArrayCtor", "16"));
Contract.EndContractBlock();            _a = ((int)b[3] << 24) | ((int)b[2] << 16) | ((int)b[1] << 8) | b[0];
_b = (short)(((int)b[5] << 8) | b[4]);
_c = (short)(((int)b[7] << 8) | b[6]);
_d = b[8];
_e = b[9];
_f = b[10];
_g = b[11];
_h = b[12];
_i = b[13];
_j = b[14];
_k = b[15];
}