C# 处理异常的银行应用程序

我想创建一个银行应用程序，它可以处理错误并抛出异常来处理发生的错误。以下是我希望程序处理的例外情况：

从账户中提取超过当前余额的款项。这将打印一条错误消息

试图在尚未创建的帐户上进行交易（存款、取款或余额）

正在尝试创建超过最大帐户数（19）的帐户

这是我的密码：

使用静态系统控制台； 名称空间库 { 公共部分类银行：表格 { 公共银行（） { 初始化组件（）； }

    private int _nextIndex = 0;

    Accounts[] arrayAccounts = new Accounts[19];


    private void createAccountButton_Click(object sender, EventArgs e)
    {
        if (string.IsNullOrEmpty(accountIDTexTBox.Text)) return;
        var account = new Accounts();
        int accountID;
        int balance = 0;

        bool success = int.TryParse(accountIDTexTBox.Text, out accountID);


        if (!int.TryParse(amountTextBox.Text, out balance))
        {
            result.Text = "Invalid Format in the Amount Fields please correct";
            //   MessageBox.Show("Invalid Format in the Amount Fields please correct");
        }


        if (balance < 300)
        {
            label5.Text = ("initial deposit must be $300 or greater");
        }

        else if (success)
        {
            account.AccountId = accountID;
            account.Balance = balance;
            arrayAccounts[_nextIndex] = account;
            OutPutLabel.Text = "Account # " + accountID + " open with balance of " + balance;
        }


        else
        {
            result.Text = ("invalid AccountID entered, Please Correct");
        }
    }

    private Accounts GetAccounts(int id)
    {

            return arrayAccounts.Where(x => x.AccountId == id).FirstOrDefault();
    }


    private void DepositRadioButton_CheckedChanged(object sender, EventArgs e)
    {
       // if (string.IsNullOrEmpty(accountIDTexTBox.Text)) return;
        int amount = 0;
        int accountID;
        bool succcess1 = int.TryParse(accountIDTexTBox.Text, out accountID);
        bool success2 = int.TryParse(amountTextBox.Text, out amount);
        try
        {
            if (succcess1 && success2 && amount > 0)
            {
                var selectedAccount = GetAccounts(accountID);
                selectedAccount.Balance += amount;
                OutPutLabel.Text = "Account # " + accountID + " deposit " + amount;
            }
            else if (!succcess1)
            {
                result.Text = "You are attempting to deposit  to a non-number ID";
            }
            else if (!success2)
            {
                result.Text = "Youu are Attempting to deposit \n "+ 
                    "to a non_Number amount  \n Please reenter the amount";
            }
        }
        catch(NullReferenceException)
        {
            result.Text = "Account has not being Created , \n Please create an Account";
        }

    }

    private void WithdrawRadioButton_CheckedChanged(object sender, EventArgs e)
    {
       // if (string.IsNullOrEmpty(accountIDTexTBox.Text)) return;
        int amount = 0;
        int accountID;
        bool success1 = int.TryParse(accountIDTexTBox.Text, out accountID);

        bool success2 = int.TryParse(amountTextBox.Text, out amount);
        try
        {
            if (success1 && success2 && amount > 0)
            {
                var selectedAccount = GetAccounts(accountID);
                selectedAccount.Balance -= amount;
                OutPutLabel.Text = amount + " withdraw from account # " + accountID;
            }


            else if (!success1)
        {
            result.Text = "You are attempting to withdraw from a non-number ID";
        }
        else if (!success2)
        {
            result.Text = "Youu are Attempting to Withdraw \n " +
                "a non_Number amount  \n Please reenter the amount";
        }

    }
        catch (NullReferenceException)
        {
            result.Text = "Account has not being created , \n Please Create Account";

        }

    }

    private void exceuteButton_Click(object sender, EventArgs e)
    {
       /// if (string.IsNullOrEmpty(accountIDTexTBox.Text)) return;
    }

    private void balanceRadioButton_CheckedChanged(object sender, EventArgs e)
    {
        int amount = 0;
        int accountID;
        bool success1 = int.TryParse(accountIDTexTBox.Text, out accountID);
        try
        {
            if (success1)
            {
                var selectedAccount = GetAccounts(accountID);
                OutPutLabel.Text = "Account # " + accountID + " has a balance of " + selectedAccount.Balance;
            }
        }
        catch (NullReferenceException)
        {
            result.Text = "Account has not being Created"
                + "\n Please create account.";

        }
    }
}

class NegativeNumberException : Exception
{
    private static string msg = "The Amount you enter is a negative number";
    public NegativeNumberException() : base(msg)
    {
    }
}

}

---

在使用异常处理这些错误方面，我确实需要帮助。

首先，您必须在代码中创建请求的异常类型，我们稍后将使用这些类型

public class InsufficientBalanceException : Exception
{
    // Exception for when a user tries to perform a withdrawal/deposit on an account with an insufficient balance of funds.
    public InsufficientBalanceException() { }

    public InsufficientBalanceException(string message)
    : base(message) { }

    public InsufficientBalanceException(string message, Exception inner)
    : base(message, inner) { }
}

public class InvalidAccountException : Exception
{
    // Exception for when a user is trying to perform an operation on an invalid account.
    public InvalidAccountException() { }

    public InvalidAccountException(string message)
    : base(message) { }

    public InvalidAccountException(string message, Exception inner)
    : base(message, inner) { }
}

public class InvalidNumberOfAccountsException : Exception
{
    // Exception for when a user is trying to create an account beyond the given limit.
    public InvalidNumberOfAccountsException() { }

    public InvalidNumberOfAccountsException(string message)
    : base(message) { }

    public InvalidNumberOfAccountsException(string message, Exception inner)
    : base(message, inner) { }
}

然后，您需要指定在什么条件下抛出这些异常中的每一个

请记住，您不希望在实体类中执行此操作，因为实体类的设计目的是尽可能简单

您很可能希望将该逻辑放入某种帮助器类中（而不是在代码中显示的UI中）。无论如何，您的代码应该类似于以下内容：

public class AccountHelper
{
    public Account GetAccount(int accountID)
    {
        /* Put some logic in here that retrieves an account object based on the accountID.
         * Return Account object if possible, otherwise return Null */
        return new Account();
    }
    public bool IsValidAccount(int accountID)
    {
        /* Put some logic in here that validates the account.
         * Return True if account exists, otherwise return False */
        return true;
    }
    public bool IsValidAmount(decimal amount)
    {
        /* Put some logic in here that validates the amount.
         * Return True if amount is valid, otherwise return False */
        return amount > 0;
    }
    public bool IsSufficientAmount(Account account, decimal amount)
    {
        /* Put some logic in here that validates the requested amount against the given account.
         * Return True if account balance is valid, otherwise return False */
        if (account == null)
            return false;

        return account.Balance >= amount;
    }
    public void DepositToAccount(int accountID, decimal amount)
    {
        Account account = null;

        if (!IsValidAmount(amount))
            throw new InvalidAmountException();

        if (!IsValidAccount(accountID))
            throw new InvalidAccountException();

        account = GetAccount(accountID);

        account.Deposit(amount);
    }
    public void WithdrawFromAccount(int accountID, decimal amount)
    {
        Account account = null;

        if (!IsValidAmount(amount))
            throw new InvalidAmountException();

        if (!IsValidAccount(accountID))
            throw new InvalidAccountException();

        account = GetAccount(accountID);

        if (!IsSufficientAmount(account, amount))
            throw new InsufficientBalanceException();

        account.Withdraw(amount);
    }
}

附加说明：

您的Accounts类应重命名为Account，如下所示： 该对象的实例表示一个帐户

您应该尝试将业务逻辑与UI分离 以后再把事情混在一起不是一个好习惯 如果必须进行更改，可能会遇到问题。它将 如果您保留了所有 您的逻辑在一个文件中，在UI之外

---

对于初学者，您永远不需要捕获

NullReferenceException

。而是执行显式空检查。业务规则应该由您的代码检查和强制执行，而不是引发异常。

public class AccountHelper
{
    public Account GetAccount(int accountID)
    {
        /* Put some logic in here that retrieves an account object based on the accountID.
         * Return Account object if possible, otherwise return Null */
        return new Account();
    }
    public bool IsValidAccount(int accountID)
    {
        /* Put some logic in here that validates the account.
         * Return True if account exists, otherwise return False */
        return true;
    }
    public bool IsValidAmount(decimal amount)
    {
        /* Put some logic in here that validates the amount.
         * Return True if amount is valid, otherwise return False */
        return amount > 0;
    }
    public bool IsSufficientAmount(Account account, decimal amount)
    {
        /* Put some logic in here that validates the requested amount against the given account.
         * Return True if account balance is valid, otherwise return False */
        if (account == null)
            return false;

        return account.Balance >= amount;
    }
    public void DepositToAccount(int accountID, decimal amount)
    {
        Account account = null;

        if (!IsValidAmount(amount))
            throw new InvalidAmountException();

        if (!IsValidAccount(accountID))
            throw new InvalidAccountException();

        account = GetAccount(accountID);

        account.Deposit(amount);
    }
    public void WithdrawFromAccount(int accountID, decimal amount)
    {
        Account account = null;

        if (!IsValidAmount(amount))
            throw new InvalidAmountException();

        if (!IsValidAccount(accountID))
            throw new InvalidAccountException();

        account = GetAccount(accountID);

        if (!IsSufficientAmount(account, amount))
            throw new InsufficientBalanceException();

        account.Withdraw(amount);
    }
}