LINQ Not In Query (Process[]).Contains does not work

           Process[] psBeforeLogin = Process.GetProcessesByName("MxOrderGenerator");

            MXXOMLib.MxEnumReturnCode ret = _MxgXOM.Login(TraderName, TraderPassword, XIPDBServer, "GMO_INTRADAY", MXXOMLib.MxEnumEncryptionMethod.MxeEncryptionMethodNone);
            Process[] psAfterLogin = Process.GetProcessesByName("MxOrderGenerator");

            var p = from rA in psAfterLogin
                    where !(from rB in psBeforeLogin select rB).Contains(rA)
                    select rA;
            Console.WriteLine(p.Count());
count =2 always, it should be one.

As it turns out, cannot use Process in select. Can use ProcessID.

          var p = from rA in psAfterLogin
                    where !(from rB in psBeforeLogin select rB.Id).Contains(rA.Id)
                    select rA;