List.Contains code not working, spent hours reading still dont get it

Question

sorry for having to ask a stupid looking question, but I tried all the advice for the last atleast 5 hours. and it hasnt made it any clearer. Im a beginner programmer and I cant see why it wouldnt work, theres no compile errors so I need your help here.

I think the problem is in the list.Contains part because everything else seems to work, but idk

my end goal was to have a sort of local register/login system (without having to use any database or sql stuff)

Here is the code:

    class CustomerList
    {
        private string _x = "x";
        private string _y = "y";
        private string _x2 = "x2";
        private string _y2 = "y2";

        private List<Customer> _list;
        //
        public string Username
        {
            get { return _x; }
            set { _x = value; }
        }
        // these are for the register
        public string Password
        {
            get { return _y; }
            set { _y = value; }
        }
        //
        public CustomerList()
        {
            _list = new List<Customer>();
        }
        //
        public string Username2
        {
            get { return _x2; }
            set { _x2 = value; }
        }
        //these are for the login
        public string Password2 {
            get { return _y2; }
            set { _y2 = value; } }
        //
        public void Register()
        {
            _list.Add(new Customer { Name = Username, Pass = Password });

        }


        public void Login()
        {
            if (_list.Contains(new Customer {Name = Username2, Pass = Password2}))
                CanLogin = true;
        }


        public bool CanLogin { get; set; } = false;
    }




   namespace App10.Model
    {
        public class Customer : IEquateable<Customer>
        {
            private string _password = "";
            private string _username = "";

        public Customer()
        {
        }
public Customer(string username, string password)
            {
                this.Pass = password;
                this.Name = username;
            }

            public string Name
            {
                get { return _username; }
                set { _username = value; }
            }

            public string Pass
            {
                get { return _password; }
                set { _password = value; }
            }

            public bool Equals(Customer other)
            {
                if (other == null)
                    return false;

                if (this._username == other._username)
                    return true;
                else
                    return false;
            }

            public override bool Equals(object obj)
            {
                if (obj == null)
                    return false;
                Customer customerObj = obj as Customer;
                if (customerObj == null)
                    return false;
                else
                    return Equals(customerObj);

            }

        public override int GetHashCode()
        {
            return this.Name.GetHashCode();
        }


        public static bool operator ==(Customer person1, Customer person2)
        {
            if (((object)person1) == null || ((object)person2) == null)
                return Object.Equals(person1, person2);

            return person1.Equals(person2);
        }

        public static bool operator !=(Customer person1, Customer person2)
        {
            if (((object)person1) == null || ((object)person2) == null)
                return !Object.Equals(person1, person2);

            return !(person1.Equals(person2));
        }

    }

    public interface IEquateable<T>
    {
    }
}


      private void register_Click_1(object sender, RoutedEventArgs e)
        {
            CustomerList ss = new CustomerList();
            ss.Username = textBox.Text;
            ss.Password = textBox1.Text;
            ss.Register();
            Frame.Navigate(typeof(BlankPage2));
}




     private void login_Click(object sender, RoutedEventArgs e)
        {
            CustomerList ss2 = new CustomerList();
            ss2.Login();
            if (ss2.CanLogin)
            {
                Frame.Navigate(typeof(MainPage));
}

Answer 1

I can see couple more issues in your code. You have a constructor that doesn't need any parameters. This can cause another developer to create a Customer object without username and password and then call methods like LogIn() or Register(). So it is better remove that constructor or have username, password as parameters in Login() and Register() methods. You are assigning customers to _list in register method. But it is more than likely that _list will not have any customers when you call LogIn(). So you may need to think about your design again.

  public void Login(string username, string password)
  {
        CanLogin = (_list.Any(c => c.Name.Equals(username, StringComparison.CurrentCultureIgnoreCase) && c.Pass.Equals(password,StringComparison.CurrentCulture));
  }

Answer 2

List.Contains works without problem as You have overriden the Equals operator. I would rather make the Name immutable to be safe with the hashcode. I did not understand the intentions in Your code completely, but building CustomerList seems suspicious, should not it preserve state between actions? I rewrote the code so it makes sense for me - behaviour has changed (the output is "Passed"):

   class CustomerList
    {
        private List<Customer> _list = new List<Customer>();

        public void Register(string user, string password)
        {
            _list.Add(new Customer(user, password));
        }

        public bool CanLogin(string user, string password)
        {
            return _list.Contains(new Customer(user, password));
        }
    }

    public class Customer
    {
        public string Name { get; protected set; }
        public string Pass { get; set; }

        public Customer(string username, string password = "")
        {
            Name = username;
            Pass = password;
        }

        public bool Equals(Customer other)
        {
            if (other == null)
                return false;

            return this.Name == other.Name;
        }

        public override bool Equals(object obj)
        {
            if (obj == null)
                return false;
            Customer customerObj = obj as Customer;
            if (customerObj == null)
                return false;
            else
                return Equals(customerObj);
        }

        public override int GetHashCode()
        {
            return this.Name.GetHashCode();
        }

        public static bool operator ==(Customer person1, Customer person2)
        {
            if (((object)person1) == null || ((object)person2) == null)
                return Object.Equals(person1, person2);

            return person1.Equals(person2);
        }

        public static bool operator !=(Customer person1, Customer person2)
        {
            return !(person1 == person2);
        }
    }


    private void button30_Click(object sender, EventArgs e)
    {
        CustomerList ss = new CustomerList();
        ss.Register("Tony", "xx");

        if (ss.CanLogin("Tony", "xx"))
        {
            Console.WriteLine("Passed");
        }
    }

Answer 3

    public void Login()
    {
        if (_list.Contains(new Customer {Name = Username2, Pass = Password2}))
            CanLogin = true;
    }

This can't possibly work, List.Contains checks if an object is already in the list. But here, you are creating a brand new object with some data, and this new object will definetly not be in the list. I'd be more appropiate find a customer which has these attributes, or better, see if there exists one. You can do so by using the List.Find() method, which will take a lambda expression which maps a Customer to a bool. You could do e.g.:

        if (_list.Find(c => c.Name == Username2 && c.Pass == Password2) != null)
            CanLogin = true;

Alternativley implement an Equals(Customer otherCustomer) function and use the equality function to check if there exists such a user in the list.

Answer 4

When List.Contains is called, it's checking for that exact object being in the list, but a new Customer is a different object, even if it holds the same values. Try changing your customer Equals method to compare the username and password instead of calling Customer.Equals again.