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

Question

抱歉不得不問一個看起來很愚蠢的問題，但我試了最後至少5小時的所有建議。它並沒有使它更清晰。 我是一個初學者程序員，我不知道爲什麼它不工作，沒有編譯錯誤，所以我需要你的幫助。

我認爲這個問題是在list.Contains部分，因爲一切似乎工作，但IDK的

我的最終目標是有幾分本地註冊/登錄系統（而無需使用任何數據庫或SQL的東西）

下面是代碼：

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

我可以在代碼中看到更多的問題。你有一個不需要任何參數的構造函數。這可能會導致其他開發人員創建一個不帶用戶名和密碼的Customer對象，然後調用方法LogIn()或Register()。因此，最好刪除該構造函數，或者在Login()和Register()方法中使用用戶名，密碼作爲參數。您正在以註冊方式將客戶分配到_list。但撥打LogIn()時，_list不會有任何客戶。所以你可能需要再次考慮你的設計。

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

當List.Contains被調用時，它的檢查，準確的對象列表之中，而是一個新的客戶是不同的對象，即使它擁有相同的值。嘗試更改您的客戶Equals方法來比較用戶名和密碼，而不是再次調用Customer.Equals。

Answer 3

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

這不可能工作，List.Contains檢查對象是否已經在列表中。但是在這裏，您正在創建一個帶有一些數據的全新對象，並且此新對象將定義爲而不是位於列表中。我會更合適地找到一個擁有這些屬性的客戶，或者更好地瞭解是否存在這樣的屬性。您可以使用List.Find()方法執行此操作，該方法將採用將Customer映射到bool的lambda表達式。你可以做例如爲：

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

Alternativley實施Equals(Customer otherCustomer)功能和使用功能的平等，以檢查是否存在列表中的這樣的用戶。

Answer 4

List.Contains的工作沒有問題，因爲您已經覆蓋了Equals運算符。我寧願讓名稱不可變以便與哈希碼一起安全。我完全不瞭解代碼中的意圖，但構建CustomerList似乎很可疑，不應該在操作之間保留狀態？我重寫了代碼，以便對我有意義 - 行爲已更改（輸出爲「通過」）：

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"); 
     } 
    }