c# - C# 按钮未返回预期值

Question

我有一个 Windows ATM 应用程序，我被困在这部分：

我有pin和firstName作为私人字符串和平衡作为私人双人。
但是，当我尝试在文本区域中显示余额时，它只会打印0. 是因为retrieveAccountInformation()有void作为回报吗？如何更改我的代码以便我可以在其他方法中使用pin、firstName和？balance

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using SQLDll;

namespace WindowsFormsApplication14
{

public partial class Form1 : Form
{
    private Connection myConnection;
    private Statement myStatement;
    private ResultSet myResultSet;

    String databaseURL = "http://www.boehnecamp.com/phpMyAdmin/razorsql_mysql_bridge.php";
    public string pin, firstName, userAccountNumber;
    public double balance;
    public double withdraw = 0;
    public double deposit = 0;
    bool buttonClicked;
    bool buttonClicked2;

    public Form1()
    {
        InitializeComponent();

        try
        {
            //connect to database
            SQL sql = new SQL();
            myConnection = sql.getConnection(databaseURL);
            //create Statement for executing SQL
            myStatement = myConnection.createStatement(databaseURL);
            loadAccountNumbers();
            updateBalance();
        }
        catch (Exception)
        {
            Console.WriteLine("Cannot connect to database server");
        }
        //close statement and database connection 
       myStatement.close();
       myConnection.close();
    }
    private void Form1_Load(object sender, EventArgs e)
    {

    }

    public void setText(string text)
    {


    }
    //load account numbers to ComboBox
    private void loadAccountNumbers()
    {
        //get all account numbers from database
        try
        {
            myResultSet = myStatement.executeQuery("SELECT accountNumber FROM accountInformation");
            // add account numbers to ComboBox
            while (myResultSet.next())
            {
                accountNumberComboBox.Items.Add(myResultSet.getString("accountNumber"));
            }
            myResultSet.close(); // close myResultSet
        }//end try
        catch (Exception)
        {
            Console.WriteLine("Error in loadAccountNumbers");
        }
    }//end method to loadAccountNumbers

    private void retrieveAccountInformation()
    {
        //get account info
        try
        {
            myResultSet = myStatement.executeQuery("SELECT pin, " +
           "firstName, balanceAmount FROM accountInformation " +
           "WHERE accountNumber = '" + userAccountNumber + "'");

            //get next result
            if (myResultSet.next())
            {
                pin = myResultSet.getString("pin");
                firstName = myResultSet.getString("firstName");
                balance = myResultSet.getDouble("balanceAmount");
            }
            myResultSet.close(); //close myResultSet
        }//end try
        catch (Exception)
        {
            Console.WriteLine("Error in retrieveAccountInformation");
        }
    }// end method retrieveAccountInformation

    //update database after withdrawing
    private void updateBalance()
    {
        //update balance in database
        try
        {
            myStatement.executeUpdate("UPDATE accountInformation" +
                           " SET balanceAmount = " + balance + " WHERE " +
                           "accountNumber = '" + userAccountNumber + "'");

        }
        catch (Exception)
        {
            Console.WriteLine("Error in updateBalace");
        }
    }//end method updateBalance

    private void accountNumberComboBox_SelectedIndexChanged(object sender, EventArgs e)
    {
        accountNumberComboBox.Enabled = false;
        numberTextField.Text = " ";
        messageTextArea.Text = "Enter your PIN #.";
        button0.Enabled = true;
        button1.Enabled = true;
        button2.Enabled = true;
        button3.Enabled = true;
        button4.Enabled = true;
        button5.Enabled = true;
        button6.Enabled = true;
        button7.Enabled = true;
        button8.Enabled = true;
        button9.Enabled = true;
        buttonDone.Enabled = true;
        retrieveAccountInformation();

    }

    private void button1_Click(object sender, EventArgs e)
    {
        setText("1");
        numberTextField.Text += "1";
        buttonEnter.Enabled = true;

    }


    private void button2_Click(object sender, EventArgs e)
    {
        setText("2");
        numberTextField.Text += "2";
        buttonEnter.Enabled = true;

    }

    private void button3_Click(object sender, EventArgs e)
    {
        setText("3");
        numberTextField.Text += "3";
        buttonEnter.Enabled = true;

    }

    private void button4_Click(object sender, EventArgs e)
    {
        setText("4");
        numberTextField.Text += "4";
        buttonEnter.Enabled = true;

    }

    private void button5_Click(object sender, EventArgs e)
    {
        setText("5");
        numberTextField.Text += "5";
        buttonEnter.Enabled = true;

    }

    private void button6_Click(object sender, EventArgs e)
    {
        setText("6");
        numberTextField.Text += "6";
        buttonEnter.Enabled = true;

    }

    private void button7_Click(object sender, EventArgs e)
    {
        setText("7");
        numberTextField.Text += "7";
        buttonEnter.Enabled = true;

    }

    private void button8_Click(object sender, EventArgs e)
    {
        setText("8");
        numberTextField.Text += "8";
        buttonEnter.Enabled = true;

    }

    private void button9_Click(object sender, EventArgs e)
    {
        setText("9");
        numberTextField.Text += "9";
        buttonEnter.Enabled = true;

    }

    private void button0_Click(object sender, EventArgs e)
    {
        setText("0");
        numberTextField.Text += "0";
        buttonEnter.Enabled = true;

    }

    private void buttonEnter_Click(object sender, EventArgs e)
    {
            numberTextField.Text = " ";
            buttonEnter.Enabled = false;
            button1.Enabled = false;
            button2.Enabled = false;
            button3.Enabled = false;
            button4.Enabled = false;
            button5.Enabled = false;
            button6.Enabled = false;
            button7.Enabled = false;
            button8.Enabled = false;
            button9.Enabled = false;
            button0.Enabled = false;
            buttonBalance.Enabled = true;
            buttonWithdraw.Enabled = true;
            buttonDeposit.Enabled = true;
            messageTextArea.Text = "Welcome," + firstName;
            updateBalance();
           if (buttonClicked == true)
            {
                withdraw = Double.Parse(numberTextField.Text);
                balance = balance - withdraw;
                updateBalance();
            }

    }

    private void buttonBalance_Click(object sender, EventArgs e)
    {
        retrieveAccountInformation();
        updateBalance();

        messageTextArea.Text=(balance.ToString());
        //display balance to messageTextArea
    }

    private void buttonWithdraw_Click(object sender, EventArgs e)
    {
        buttonBalance.Enabled = false;
        buttonWithdraw.Enabled = false;
        button0.Enabled = true;
        button1.Enabled = true;
        button2.Enabled = true;
        button3.Enabled = true;
        button4.Enabled = true;
        button5.Enabled = true;
        button6.Enabled = true;
        button7.Enabled = true;
        button8.Enabled = true;
        button9.Enabled = true;
        messageTextArea.Text = "Enter withdrawal amount:";
        buttonClicked = true;

    }

    private void buttonDone_Click(object sender, EventArgs e)
    {
        button1.Enabled = false;
        button2.Enabled = false;
        button3.Enabled = false;
        button4.Enabled = false;
        button5.Enabled = false;
        button6.Enabled = false;
        button7.Enabled = false;
        button8.Enabled = false;
        button9.Enabled = false;
        button0.Enabled = false;
        buttonEnter.Enabled = false;
        buttonBalance.Enabled = false;
        buttonWithdraw.Enabled = false;
        buttonDone.Enabled = false;
        buttonDeposit.Enabled = false;
        accountNumberComboBox.Enabled = true;
        messageTextArea.Text = "Please select your account number.";


    }

    private void buttonDeposit_Click(object sender, EventArgs e)
    {
        buttonBalance.Enabled = false;
        buttonWithdraw.Enabled = false;
        button0.Enabled = true;
        button1.Enabled = true;
        button2.Enabled = true;
        button3.Enabled = true;
        button4.Enabled = true;
        button5.Enabled = true;
        button6.Enabled = true;
        button7.Enabled = true;
        button8.Enabled = true;
        button9.Enabled = true;
        messageTextArea.Text = "Enter deposit amount:";
        buttonClicked2 = true;

    }
}

}

score 0 · Accepted Answer

因为你正在使用myResultSet.next().

如果您有两个 SQL 语句，例如

SELECT * FROM Users  
Go  
SELECT * FROM Accounts  
Go

if (myResultSet.next())-> 这将读取从第二个 SQL 语句返回的数据。

我认为这可能是您想要的：

string connString = AppConfigurationManager.GetAppSetting("ConnectionString",IsQA);
using (var conn = new SqlConnection(connString))
{
    conn.Open();
    using (SqlCommand sqlCommand = new SqlCommand("SELECT pin, " +
"firstName, balanceAmount FROM accountInformation " +
"WHERE accountNumber = '" + userAccountNumber + "'", conn))
    {
        sqlCommand.CommandType = CommandType.Text;
        SqlDataReader dr = null;
        try
        {
            dr = sqlCommand.ExecuteReader();
            while (dr.Read())
            {
                pin = dr.getString("pin");
                firstName = dr.getString("firstName");
                balance = dr.getDouble("balanceAmount");
            }
        }
        catch (SqlException ex)
        {



    }
    catch (Exception ex)
    {

    }
    finally
    {
        //clean up resources that access Data
        if (dr != null)
        {
            dr.Close();
        }
    }
}

score 0 · Accepted Answer

在我看来，您可以使用“out”或“ref”

private void retrieveAccountInformation(out string pin, out string firstname, out double balance)
{
    //get account info
    try
    {
        myResultSet = myStatement.executeQuery("SELECT pin, " +
       "firstName, balanceAmount FROM accountInformation " +
       "WHERE accountNumber = '" + userAccountNumber + "'");
        //get next result
        if (myResultSet.next())
        {
            pin = myResultSet.getString("pin");
            firstName = myResultSet.getString("firstName");
            balance = myResultSet.getDouble("balanceAmount");
        }
        myResultSet.close(); //close myResultSet
    }//end try
    catch (Exception)
    {
        Console.WriteLine("Error in retrieveAccountInformation");
    }
}// end method retrieveAccountInformation

private void buttonBalance_Click(object sender, EventArgs e)
{
    string pin = "";
    string firstname = "";
    double balance = 0;

    retrieveAccountInformation(out string pin, out string firstname, out double balance);

    updateBalance();
    messageTextArea.Text=(balance.ToString());
    //display balance to messageTextArea
}

score -1 · Accepted Answer

因为 pin、firstName、balance 是局部变量，并且此方法是私有 void，所以如果您想从 void 方法中获取值。使用输入、输出变量。这使得一个方法可以返回多个值

此外， updateBalance() 做什么？它声明了变量并调用了retrieveAccountInformation 方法？？？？

例子：

private void retrieveAccountInformation(out string pin,out string firstname,out double balance)
{
 //get account info
 try
 {
        myResultSet = myStatement.executeQuery("SELECT pin, " +
       "firstName, balanceAmount FROM accountInformation " +
       "WHERE accountNumber = '" + userAccountNumber + "'");

        //get next result
        if (myResultSet.next())
        {
            pin = myResultSet.getString("pin");
            firstName = myResultSet.getString("firstName");
            balance = myResultSet.getDouble("balanceAmount");
        }
        myResultSet.close(); //close myResultSet
    }//end try
    catch (Exception)
    {
        Console.WriteLine("Error in retrieveAccountInformation");
    }
}// end method retrieveAccountInformation

private void buttonBalance_Click(object sender, EventArgs e)
{

    string pin, firstname;
    double balance;
    retrieveAccountInformation(pin, firstname, balance);
    messageTextArea.Text=(balance.ToString());
    //display balance to messageTextArea
}

c# - C# 按钮未返回预期值

3 回答 3

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