c# - WPF 和 C# : Trouble with Classes and Interfaces

Question

我正在开发一个银行账户程序。除了主窗口类之外，我还使用了一个基类、一个接口(interface)和两个派生类。我正在制作一个 WPF 应用程序，到目前为止，我能够在该应用程序中使用类对象的 ArrayList 填充一个 ListBox 就好了。但是，当我去修改 ArrayList 中的任何对象时，我在正确地重新填充 ListBox 时遇到了困难。任何帮助将不胜感激!

这是我的主窗口代码:

 public partial class MainWindow : Window
 {
    ArrayList bankAccountList = new ArrayList();

    BankAccount savingsAccount = new SavingsAccount("New", "Account", "newaccount");
    BankAccount checkingAccount = new CheckingAccount("New", "Account", "newaccount");
    IAccount iAccount;
    string typeOfAccount = "";

    public MainWindow()
    {
        InitializeComponent();
    }

    //When the user pushes the "Add A Saving Account" button, a new savings account is added to the ArrayList and displayed in the app.
    private void btnAddAccount_Click(object sender, RoutedEventArgs e)
    {
        iAccount = (IAccount)savingsAccount;

        savingsAccount.Deposit(0.00m);

        bankAccountList.Add(savingsAccount);
        lbxExistingAccounts.Items.Add(iAccount.AccountInformation());
        typeOfAccount = "savings";
    }

    //When the user pushes the "Add A Checking Account" button, a new checking account is added to the ArrayList and displayed in the app.
    private void btnAddCheckingAccount_Click(object sender, RoutedEventArgs e)
    {
        iAccount = (IAccount)checkingAccount;

        checkingAccount.Deposit(0.00m);

        bankAccountList.Add(checkingAccount);
        lbxExistingAccounts.Items.Add(iAccount.AccountInformation());
        typeOfAccount = "checking";
    }

    //When the user pushes the "Delete Account" button, the account is removed, and this change is shown in the app.
    private void btnDeleteAccount_Click(object sender, RoutedEventArgs e)
    {
        lbxExistingAccounts.Items.RemoveAt(lbxExistingAccounts.Items.IndexOf(lbxExistingAccounts.SelectedItem));
    }

    //The user can push the "Submit Changes" button to submit his or her changes to the number and name of the account.
    private void btnSubmitChanges_Click(object sender, RoutedEventArgs e)
    {
        try
        {

            for (int index = 0; index < bankAccountList.Count; index++)
            {
                if (index == lbxExistingAccounts.SelectedIndex)
                {
                    if (typeOfAccount == "savings")
                    {
                        savingsAccount.AccountNumber = tbxAccountNumber.Text;
                        savingsAccount.AccountOwnerFirstName = tbxFirstName.Text;
                        savingsAccount.AccountOwnerLastName = tbxLastName.Text;
                    }

                    else if (typeOfAccount == "checking")
                    {
                        checkingAccount.AccountNumber = tbxAccountNumber.Text;
                        checkingAccount.AccountOwnerFirstName = tbxFirstName.Text;
                        checkingAccount.AccountOwnerLastName = tbxLastName.Text;
                    }
                }
            }
            lbxExistingAccounts.Items.Clear();
            foreach (object accountObject in bankAccountList)
            {
                lbxExistingAccounts.Items.Add(accountObject);
            }
        }
        catch (FormatException)
        {
            MessageBox.Show("You may enter changes as letters, numbers, or both.");
        }

    }

这是我的界面代码:

interface IAccount
{
    void SetAccountBalance(decimal accountBalance);
    string AccountInformation();
}

这是我的基类代码:

    abstract class BankAccount
{
    public string AccountNumber { get; set; }
    public string AccountOwnerFirstName { get; set; }
    public string AccountOwnerLastName { get; set; }
    public decimal AccountBalance { get; set; }
    public decimal AnnualInteresetRate { get; set; }
    public string TypeOfAccount { get; set; }

    public BankAccount(string accountOwnerFirstName, string accountOwnerLastName, string accountNumber)
    {
        AccountOwnerFirstName = accountOwnerFirstName;
        AccountOwnerLastName = accountOwnerLastName;
        AccountNumber = accountNumber;
    }

    public abstract void Deposit(decimal amount);

    public abstract void Withdraw(decimal amount);

    public decimal CalculateInterest()
    {
        return (this.AccountBalance * this.AnnualInteresetRate) / 100;
    }
} 

这是我的派生类之一。我做的都差不多。

    class SavingsAccount : BankAccount, IAccount
{
    public SavingsAccount(string accountOwnerFirstName, string accountOwnerLastName, string accountNumber)
        : base(accountOwnerFirstName, accountOwnerLastName, accountNumber)
    {
        AnnualInteresetRate = 0.95m;
    }

    public override void Deposit(decimal amount)
    {
        AccountBalance = AccountBalance + amount;
    }

    public override void Withdraw(decimal amount)
    {
        AccountBalance = AccountBalance - amount;
    }

    public void SetAccountBalance(decimal accountBalance)
    {
        AccountBalance = accountBalance;
    }

    public string AccountInformation()
    {
        return "Savings Account \n  " + AccountOwnerFirstName + " " + AccountOwnerLastName + ", Account#: " + AccountNumber + ", Balance: $" + AccountBalance;
    }
}

Answer 1

看起来您才刚刚起步，这很好，因为您将要重新做一些事情。

1. 您不需要将派生对象转换为它们的基类型。这种类型的转换称为“向上转换”，无需任何转换即可自动工作。

2. 您发布的代码高度“类似于 WinForms”，这在 WPF 中不是一个好的方法。首先让您的帐户列表成为一个 ObservableCollection 并将您的 ListBox 的 ItemsSource 绑定(bind)到它。

属性看起来像:

public ObservableCollection<BankAccount> Accounts {get; set;}

为简洁起见，实际上应该使用 INotifyPropertyChanged 和绑定(bind):

<ListBox "ItemsSource={Binding Accounts}"/>

当然，这应该放在 View 模型类中，但您可以通过设置代码隐藏开始:

DataContext = this;

一旦一切正常，您的所有文本框都应该绑定(bind)到数据对象或 View 本身的属性。

这里有一篇关于将 MVVM 与 WPF 结合使用的精彩教程 (MSDN)。相信我，使用这种设计模式将使您使用 WPF 的工作变得非常容易、更具可扩展性，并且您会发现 WPF 基本上就是为使用它而设计的。使用 WinForms 方法只会让您感到痛苦。

如果我能提供进一步帮助或澄清任何问题，请告诉我!