try
{
    sqlCommandWithdraw.Connection.Open();
    sqlCommandWithdraw.Parameters["@cardNumber"].Value = Class1.cardNumber;
    readdata = sqlCommandWithdraw.ExecuteReader();

    while (readdata.Read())
    {
        balanceDB = decimal.Parse(readdata["balance"].ToString());
    }

    decimal withdrawAmm = Convert.ToDecimal(textWithdraw.Text);
    balanceDB = balanceDB - withdrawAmm;
    sqlCommandWithdraw.Connection.Close();

    sqlCommandUpdate.Connection.Open();
    sqlCommandUpdate.Parameters["@cardNumber"].Value = Class1.cardNumber;
    sqlCommandUpdate.Parameters["@balanceDB"].Value = Class1.cardNumber;
    readdata = sqlCommandUpdate.ExecuteReader();
    MessageBox.Show(balanceDB +" Successfully Withdrawn");
}


我正在为ATM机编写代码,我在提款上有些东西,看起来不错,但似乎并没有改变余额以反映数据库中的提款

我的命令是这样的(更新)

update dbo.Accounts
set balance = @balanceDB
from dbo.ATMCards
INNER JOIN dbo.Accounts ON dbo.ATMCards.accountID = dbo.Accounts.accountID
where (dbo.ATMCards.cardNumber = @cardNumber)


这是我选择数据的命令

select dbo.Accounts.balance
from dbo.ATMCards
INNER JOIN dbo.Accounts ON dbo.ATMCards.accountID = dbo.Accounts.accountID
where (dbo.ATMCards.cardNumber = @cardNumber)


似乎运行得很好,添加了消息框以进行检查,感谢您的帮助!

最佳答案

您正在将信用卡号传递给参数@balanceDB-这是第一个错误。其次,您不使用ExecuteReader执行更新-而是使用ExecuteNonQuery

编辑
我会为您做一些清理工作:

try
{
    try
    {
        sqlCommandWithdraw.Connection.Open();
        sqlCommandWithdraw.Parameters["@cardNumber"].Value = Class1.cardNumber;

        // Make sure to dispose of the reader, which also closes the reader, which
        // is important, because you can't perform any other selects on a connection
        // with an open reader!
        using (SqlDataReader reader = sqlCommandWithdraw.ExecuteReader())
        {
            // You will only get one line - also, your code also only evaluates
            // one result, so we can do the following:
            if (reader.Read())
            {
                balanceDB = decimal.Parse(readdata["balance"].ToString());
            }
        }
    }
    finally
    {
        sqlCommandWithdraw.Connection.Close();
    }

    decimal withdrawAmm = Convert.ToDecimal(textWithdraw.Text);
    balanceDB = balanceDB - withdrawAmm;

    try
    {
        sqlCommandUpdate.Connection.Open();
        sqlCommandUpdate.Parameters["@cardNumber"].Value = Class1.cardNumber;
        sqlCommandUpdate.Parameters["@balanceDB"].Value = balanceDB;

        sqlCommandUpdate.ExecuteNonQuery();
        MessageBox.Show(balanceDB +" Successfully Withdrawn");
    }
    finally
    {
        sqlCommandUpdate.Connection.Close();
    }


}

10-07 19:32
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