C# 更新数据库错误

本文关键字：错误 数据库 更新 | 更新日期: 2023-09-27 18:28:19

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    MessageBox.Show(balanceDB +" Successfully Withdrawn");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，我对提款有点不满意，它看起来不错，但似乎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，添加了消息框以检查它，感谢您的任何帮助赞赏它！

C# 更新数据库错误

您正在将信用卡号传递给参数@balanceDB - 这是第一个错误。其次，不要使用 ExecuteReader 来执行更新 - 请改用ExecuteNonQuery。

编辑
我会为你做一些清理：

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();
    }

}

您

为 @balanceDB 参数传递了错误的值。它应该是余额金额。但是您正在传递卡号。

 sqlCommandUpdate.Parameters["@balanceDB"].Value = Class1.cardNumber;

应改为 

 sqlCommandUpdate.Parameters["@balanceDB"].Value = balanceDB ;

这行对我来说很可疑：

sqlCommandUpdate.Parameters["@balanceDB"].Value = Class1.cardNumber;

这应该Class1.balance吗？

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