Question

我在Visual Studio 2012中创建了一个控制台应用程序，它根据原则，贷款和利息计算贷款。我现在正在尝试将此控制台应用程序转换为Windows窗体。我觉得这个过程应该只是关闭控制台提示并用Windows Forms txt和单选按钮替换它。
这是我的控制台应用程序的代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace MortgageCalculator
{
    public class MortgageCalculator
    {

        public static void Main(string[] args)
        {
            // declare variables
            double principle = 0; 
            double years = 0;
            double interest = 0;
            string principleInput, yearsInput, interestInput;


            // User input for Principle amount in dollars
            Console.Write("Enter the loan amount, in dollars(0000.00): ");
            principleInput = Console.ReadLine();
            principle = double.Parse(principleInput);
            //Prompt the user to reenter any illegal input
            if (principle < 0)
            {
                Console.WriteLine("The value for the mortgage cannot be a negative value");
            principle = 0;
        }


        // User input for number of years
        Console.Write("Enter the number of years: ");
        yearsInput = Console.ReadLine();
        years = double.Parse(yearsInput);
        //Prompt the user to reenter any illegal input
        if (years < 0)
        {
            Console.WriteLine("Years cannot be a negative value");
            years = 0;
        }

        // User input for interest rate
        Console.Write("Enter the interest rate(%): ");
        interestInput = Console.ReadLine();
        interest = double.Parse(interestInput);
        //Prompt the user to reenter any illegal input
        if (interest < 0)
        {
            Console.WriteLine("The value for the interest rate cannot be a negative value");
            interest = 0;
        }

        //Calculate the monthly payment
        //ADD IN THE .Net function call Math.pow(x, y) to compute xy (x raised to the y power). 
        double loanM = (interest / 1200.0);
        double numberMonths = years * 12;
        double negNumberMonths = 0 - numberMonths;
        double monthlyPayment = principle * loanM / (1 - System.Math.Pow((1 + loanM),   negNumberMonths));

        //double totalPayment = monthlyPayment;


        //Output the result of the monthly payment
        Console.WriteLine(String.Format("The amount of the monthly payment is: {0}{1:0.00}", "$", monthlyPayment));
        Console.WriteLine();
        Console.WriteLine("Press the Enter key to end. . .");
        Console.Read();

        }
    }
}

我现在想将上面的内容转换为Windows窗体应用程序。我想要的设计是我的形式原则作为文本框，然后我有三个单选按钮控件。一个15年，30年和其他（这是另一个文本框）。利率为ComboBox，利率为1-15％。这是我第一次尝试创建Windows窗体，我将在下面展示我的内容。我想我的主要问题是如何计算我的monthlyPayment以及如何将其导入Windows窗体应用程序。任何对正确方向的帮助都将受到赞赏。

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

   namespace LoanCalc
   {
   public partial class Form1 : Form
   {
       public Form1()
       {
           InitializeComponent();
       }

       private void Form1_Load(object sender, EventArgs e)
       {
           tbLoanDuration.Enabled = false;
       }

       private void rb30years_CheckedChanged(object sender, EventArgs e)
       {
           if (rbOther.Checked)
               tbLoanDuration.Enabled = true;
           else
               tbLoanDuration.Enabled = false;
       }

       private void button1_Click(object sender, EventArgs e)
       {

          if (cbLoanRate.SelectedIndex > -1)
           {
               string s = cbLoanRate.SelectedItem.ToString();
           }

           string msg = string.Format("Your total monthly payment is", MonthlyPayment);



        }

       private void tbLoanDuration_TextChanged(object sender, EventArgs e)
       {
           double years = 0;
           Control ctrl = (Control)sender;

           bool success = Double.TryParse(tbLoanDuration.Text, out years);
           if (!success)
           {
               errorProvider1.SetError(ctrl, "This is not a valid number");
           }  
           else
           {
               errorProvider1.SetError(ctrl, "");
           }

       }

       private double MonthlyPayment()
       {
           double loanM = (interest / 1200.0);
           double numberMonths = years * 12;
           double negNumberMonths = 0 - numberMonths;
           double monthlyPayment = principle * loanM / (1 - System.Math.Pow((1 + loanM), negNumberMonths));

           return monthlyPayment;
       }




       public double interest { get; set; }
       public double years { get; set; }
       public double principle { get; set; }

       private void tbPrinciple_TextChanged(object sender, EventArgs e)
       {

           double principle = Double.Parse(tbPrinciple.Text);
           //Prompt the user to reenter any illegal input
           if (principle < 0)
           {
               Console.WriteLine("The value for the mortgage cannot be a negative value");
               principle = 0;
           }
       } 
    }

}

Answer 1

正如PhaDaPhunk所说，让我们确切地知道您遇到的问题（错误信息，不确定如何获取数据等）对我们帮助您非常有帮助。基于你的问题的一般性，我看到了一些事情，我在评论中提到了几个，我将在这里详细说明。

您在代码中定义了三个属性：

   public double interest { get; set; }
   public double years { get; set; }
   public double principle { get; set; }

在风格上，属性通常是有资格的（即public double Interest）。

当相应的控件的值或所选项目发生变化时，您似乎正在为这些属性分配值 - 至少有时是这样。我会对您的代码进行以下更改：

private void rb30years_CheckedChanged(object sender, EventArgs e)
{

    if (rb15Years.Checked)
    {
        years = 15;
        tbLoanDuration.Enabled = false;
    }
    else if (rb30Years.Checked)
    {
        years = 30;
        tbLoanDuration.Enabled = false;
    }       
    else if (rbOther.Checked)
    {
        tbLoanDuration.Enabled = true;
    }
}

我猜你15年和30年的单选按钮ID是什么。如果选择15或30，这也会为year属性赋值。

对于您的计算，您需要调用方法并将返回结果格式化为字符串：

private void button1_Click(object sender, EventArgs e)
{

    double selectedRate = 0;

    if (cbLoanRate.SelectedIndex > 1 && double.TryParse(cbLoanRate.SelectedItem, out selectedRate))
    {
        interest = selectedRate;

        lblMonthlyPayment.Text = string.Format("Your total monthly payment is {0}{1:0.00}", "$", MonthlyPayment());
    }
}

这是大部分变化的地方。

首先，如果cbLoanRate的selectedIndex大于1，并且所选项目可以转换为double，则进行计算，否则不执行任何操作（或显示错误）。

如果selectedIndex大于1且所选项目可以解析为doulbe，请将selectedRate的结果分配给interest属性。

我不确定您打算使用msg做什么，但是假设您有一个名为Label的{{1}}来显示每月付款。我使用了与控制台应用程序中相同的字符串格式，并直接调用了方法lblMonthlyPayment。看起来您试图使用MonthlyPayment()方法中的monthlyPayment，但这不起作用，因为它只在方法内的范围内（可访问）。然后将方法的返回值分配给MonthlyPayment的Text属性。

最后，我还会改变你的lblMonthlyPayment：

tbPrinciple_TextChanged

最后，对private void tbPrinciple_TextChanged(object sender, EventArgs e) { // Use TryParse instead of Parse in case the user enters text or some // other non-numeric character double enteredPrinciple = 0; if (double.TryParse(tbPrincipal.Text, out enteredPrinciple)) { if (enteredPrinciple < 0) { // Console.WriteLine won't display anything to the user MessageBox.Show("The value for the mortgage cannot be a negative value"); } else { // Assign it to the property principle = enteredPrinciple; } } else { // Prompt the user to enter a numeric value MessageBox.Show("The value for the mortgage must be a numeric value"); } }方法稍作修改：

tbLoanDuration_TextChanged

这些变化中的大多数都是次要的 - 总而言之，你正走在正确的道路上。我没有测试过这段代码，并且在大约2年内没有完成WinForms，所以可能会有一些语法问题，但这应该指向正确的方向。

尝试将控制台应用程序转换为VS 2012中的Windows窗体

1 个答案: