尝试在VS 2012中将控制台应用程序转换为Windows窗体

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把控制台提示换成Windows窗体文本和单选按钮。
以下是我的控制台应用程序代码:

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();
        }
    }
}

我现在想把上面的转换成一个Windows窗体应用程序。我想要的设计是我的形式与原则作为一个文本框，然后我有三个单选按钮控件。一个是15年，一个是30年，还有一个是其他(这是另一个文本框)。利率是一个组合框，利率从1- 15%。这是我第一次尝试创建一个Windows窗体，我将在下面显示我目前所拥有的。我想我的主要问题是与我的每月付款的计算，以及如何将其导入到一个Windows窗体应用程序。任何帮助到正确的方向将不胜感激。

   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;
           }
       } 
    }
}