我如何告訴我的程序它應該繼續從數字中減去？

Question

我有以下代碼：

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }

    double salaryAmount;
    double subtractAmount;
    double newSalaryAmount;
    string amountBackToString;

    private void Button1_Click(object sender, RoutedEventArgs e)
    {
        try
        {
            salaryAmount = double.Parse(TextBox1.Text);
            label1.Content = salaryAmount.ToString();
        }
        catch (Exception)
        {

            MessageBox.Show("This was not a valid input.");
        } 
    }

    private void Button2_Click(object sender, RoutedEventArgs e)
    {
        try
        {
            subtractAmount = double.Parse(TextBox2.Text);
            newSalaryAmount = salaryAmount - subtractAmount;
            label1.Content = newSalaryAmount.ToString();
        }
        catch (Exception)
        {
            MessageBox.Show("This was not a valid input.");
        }
    }

    private void Button3_Click(object sender, RoutedEventArgs e)
    {
        amountBackToString = Convert.ToString(newSalaryAmount);
        string[] currentAmount = { amountBackToString };
        File.WriteAllLines(@"C:\Users\Silas\Downloads\Lohn.txt", currentAmount);
    }

    private void Button4_Click(object sender, RoutedEventArgs e)
    {
        string text = File.ReadAllText(@"C:\Users\Silas\Downloads\Lohn.txt");
        label1.Content = text;
        salaryAmount = Convert.ToDouble(label1.Content);
    }
}

問題是它每次都會將數字重置為初始輸入，然后減去，但它應該采用初始輸入並不斷從中減去

我的程序是薪水計算器。

Answer 1

您只需要將newSalaryAmount應用於當前的salaryAmount

private void Button2_Click(object sender, RoutedEventArgs e)
{
    try
    {
        subtractAmount = double.Parse(TextBox2.Text);
        newSalaryAmount = salaryAmount - subtractAmount;

        //Set the new current salary
        salaryAmount = newSalaryAmount
        label1.Content = newSalaryAmount.ToString();
    }
    catch (Exception)
    {
        MessageBox.Show("This was not a valid input.");
    }
} 

在您的情況下， salaryAmount將始終保持從TextBox1.Text給定的初始值，因此當您再次減少該值時，它將采用此后沒有改變的值。