每次取款或存款后更新余额

Question

我是 C# 新手，并且已经在这个项目上工作了一段时间。我已经解决了我以前的问题并完成了一个工作程序。但是，我现在陷入了一个新问题。我有一个银行程序，可以取款或存款并增加初始余额。但是，在初始存款或取款后，我无法更新到新余额。

TL;DR：初始余额 = 1000。存入 100。新余额 = 1100。再存入 100，它不会更新，余额将保持在 1100。

Account.cs

namespace Account_Teller
{
    class Account
   {   

    private decimal _amount;
    public decimal balance;

    public decimal Balance { get; }

    public Account (decimal pBalance)
    {
        this.Balance = pBalance;
    }

    public decimal Amount
    {
        get
        {
            return _amount;              
        }
        set
        {
            if (value < 0)
            {
                throw new ArgumentException("Please enter an amount greater than 0");                  
            }
            else
            {
                _amount = value;
            }
        }
    }

    public decimal Deposit()
    {          
        balance = Balance + _amount;
        return balance;
    }

    public decimal Withdrawl()
    {                    

        balance = Balance - _amount;


        if (balance < 0)
        {
            throw new ArgumentException("Withdrawing " + _amount.ToString("C") + " would leave you overdrawn!");
        }
        return balance;
    }
}

}

Main.cs

namespace Account_Teller
{
public partial class Form1 : Form
{


    public Form1()
    {
        InitializeComponent();
    }

    Account acc = new Account(1000);


    private void btnWithdraw_Click(object sender, EventArgs e)
    {
        lblBalance.Text = acc.Balance.ToString("C");
        try
        {               
            acc.Amount = decimal.Parse(txtAmount.Text);               
            lblBalance.Text = acc.Withdrawl().ToString("C");               
        }
        catch (FormatException ex)
        {
            MessageBox.Show(ex.Message);
        }
        catch (ArgumentException ex)
        {
            MessageBox.Show(ex.Message);
        } 
        catch (Exception error)
        {
            MessageBox.Show(error.Message);
        }
    }

    private void btnDeposit_Click(object sender, EventArgs e)
    {
        try
        {

            acc.Amount = decimal.Parse(txtAmount.Text);                
            lblBalance.Text = acc.Deposit().ToString("C");
        }
        catch (FormatException ex)
        {
            MessageBox.Show(ex.Message);
        }    
        catch (ArgumentException ex)
        {
            MessageBox.Show(ex.Message);
        }
        catch (Exception error)
        {
            MessageBox.Show(error.Message);
        }
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        lblBalance.Text = acc.Balance.ToString("C");
    }
}

}

Answer 1

您的代码中没有任何内容将属性Balance 与字段balance 联系起来。就 C# 而言，它们是两个独立的变量。

您的Balance 可能应该定义为：

public decimal Balance { get; private set; }

那么你根本就没有balance 字段。

你班上的其他人应该是这样的：

public class Account
{
    public decimal Balance { get; private set; }

    public Account(decimal balance)
    {
        this.Balance = balance;
    }

    public void Deposit(decimal amount)
    {
        if (amount < 0m)
        {
            throw new ArgumentException("Please enter an amount greater than 0");
        }
        this.Balance = this.Balance + amount;
    }

    public void Withdraw(decimal amount)
    {
        if (this.Balance - amount < 0m)
        {
            throw new ArgumentException("Withdrawing " + amount.ToString("C") + " would leave you overdrawn!");
        }
        this.Balance = this.Balance - amount;
    }
}

这将是此代码的更典型实现。

然后您将编写这种代码来使用该类：

acc.Withdraw(decimal.Parse(txtAmount.Text));
lblBalance.Text = acc.Balance.ToString("C");               

Answer 2

因为你没有在 balance 和 Balance 之间设置约束。还有一件事，不要公开平衡

class Account
    {

        private decimal _amount;
        private decimal _balance;

        public decimal Balance
        {
            get { return _balance; }
            private set { _balance = value; }
        }

        public Account(decimal pBalance)
        {
            this.Balance = pBalance;
        }

        public decimal Amount
        {
            get { return _amount; }
            set
            {
                if (value < 0)
                {
                    throw new ArgumentException("Please enter an amount greater than 0");
                }
                else
                {
                    _amount = value;
                }
            }
        }

        public decimal Deposit()
        {
            _balance = _balance + _amount;
            return _balance;
        }

        public decimal Withdrawl()
        {
            if (_balance - _amount < 0)
            {
                throw new ArgumentException("Withdrawing " + _amount.ToString("C") + " would leave you overdrawn!");
            }
            _balance = _balance - _amount;
            return _balance;
        }
    }