C#计算器给定代码

Question

我正在做家庭作业，在这项作业中我得到了入门代码。我们正在学习我以前做过的类(class)，但似乎被这些类(class)淹没了。入门代码让我感到困惑，我个人宁愿自己开始作业。我对此有几个问题，我想知道是否有人可以帮助我解释它，以便我可以完成这项任务。

我最大的问题很简单。如果您有计算器，您会得到第一个数字，然后是第二个数字。所以如果用户输入 1 + 1 那么你基本上就有了你的数字。我们得到的代码没有 firstNumber 和 secondNumber。相反，如果我理解正确的话，它有 displayValue 和 currentValue(？)我不完全确定这些值是如何存储的，我相信它们已经存储了？

这真的是我想要找出的，然后我是否正确地编写了我的类(class)代码，因为我挂断了我输入的实际数字是如何存储在程序中的。

这是提供的代码。

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;

namespace Calculator
{
public partial class frmCalculator : Form
{
    public frmCalculator()
    {
        InitializeComponent();
    }

    // The following fields are used to store the value that's currently
    // displayed by the calculator. displayString is a string value that's
    // constructed as the user clicks numeric keys and the decimal and +/-
    // key. The Convert.ToDecimal method is then used to convert this to a decimal
    // field that's stored in displayValue.
    private string displayString;
    private decimal displayValue;

    // The following bool fields are used to control numeric entry.
    // newValue indicates whether the calculator is ready to receive a
    // new numeric value. Once the user clicks a digit button, newValue is
    // set to false. When the user clicks a button that "enters" the value, 
    // such as Add or Equals, newValue is set to true so the user can enter 
    // another value.
    // decimalEntered is used to restrict the entry to a single decimal point.
    // It is set to true whenever newValue is set to true, and it is set to 
    // false whenever the user clicks the decimal point button.
    private bool newValue;
    private bool decimalEntered;

    private Calculator calc = new Calculator();

    private void Form1_Load(object sender, System.EventArgs e)
    {
        displayValue = 0;
        displayString = displayValue.ToString();
        newValue = true;
        decimalEntered = false;
    }

    // This method handles the 0 through 9 keys, appending the digit clicked
    // to the displayString field. 
    private void btnNumber_Click(object sender, System.EventArgs e)
    {
        if (newValue)
        {
            displayString = "";
            newValue = false;
        }
        displayString += ((Button)sender).Tag.ToString();
        displayValue = Convert.ToDecimal(displayString);
        txtDisplay.Text = displayValue.ToString();
    }

    // This method removes the last character from the displayString field.
    private void btnBackSpace_Click(object sender, System.EventArgs e)
    {
        if (displayString.Length > 1)
        {
            displayString = displayString.Substring(0, displayString.Length - 1);
            displayValue = Convert.ToDecimal(displayString);
            txtDisplay.Text = displayValue.ToString();
        }
        else
        {
            displayString = "";
            displayValue = 0;
            txtDisplay.Text = displayValue.ToString();
        }

    }

    private void btnClear_Click(object sender, System.EventArgs e)
    {
        calc.Clear();
        displayString = "";
        displayValue = 0;
        txtDisplay.Text = displayValue.ToString();
        newValue = true;
        decimalEntered = false;
    }

    // This method appends a decimal point to the displayString field if the
    // user has not already entered a decimal point.
    private void btnDecimal_Click(object sender, System.EventArgs e)
    {
        if (newValue)
        {
            displayString = "0";
            newValue = false;
        }
        if (!decimalEntered)
        {
            displayString += ".";
            displayValue = Convert.ToDecimal(displayString);
            txtDisplay.Text = displayValue.ToString();
            decimalEntered = true;
        }
    }

    private void btnSign_Click(object sender, System.EventArgs e)
    {
        displayValue = -displayValue;
        txtDisplay.Text = displayValue.ToString();
    }

    private void btnAdd_Click(object sender, System.EventArgs e)
    {
        calc.Add(displayValue);
        newValue = true;
        decimalEntered = false;
        displayValue = calc.CurrentValue;
        txtDisplay.Text = displayValue.ToString();
    }

    private void btnSubtract_Click(object sender, System.EventArgs e)
    {
        calc.Subtract(displayValue);
        newValue = true;
        decimalEntered = false;
        displayValue = calc.CurrentValue;
        txtDisplay.Text = displayValue.ToString();
    }

    private void btnMultiply_Click(object sender, System.EventArgs e)
    {
        calc.Multiply(displayValue);
        newValue = true;
        decimalEntered = false;
        displayValue = calc.CurrentValue;
        txtDisplay.Text = displayValue.ToString();
    }

    private void btnDivide_Click(object sender, System.EventArgs e)
    {
        calc.Divide(displayValue);
        newValue = true;
        decimalEntered = false;
        displayValue = calc.CurrentValue;
        txtDisplay.Text = displayValue.ToString();
    }

    //private void btnSqrt_Click(object sender, System.EventArgs e)
    //{
      //  calc.SquareRoot(displayValue);
        //displayValue = calc.CurrentValue;
        //txtDisplay.Text = displayValue.ToString();
    //}

    //private void btnReciprocal_Click(object sender, System.EventArgs e)
    //{
      //  try
       // {
         //   calc.Reciprocal(displayValue);
           // displayValue = calc.CurrentValue;
            //txtDisplay.Text = displayValue.ToString();
        //}
        //catch (DivideByZeroException)
        //{
          //  displayValue = 0;
           // txtDisplay.Text = "Cannot divide by zero.";
            //newValue = true;
            //decimalEntered = false;
        //}
    }

    private void btnEquals_Click(object sender, System.EventArgs e)
    {
        try
        {
            if (newValue)
                calc.Equals();
            else
                calc.Equals(displayValue);
            displayValue = calc.CurrentValue;
            txtDisplay.Text = displayValue.ToString();
            newValue = true;
            decimalEntered = false;
        }
        catch (DivideByZeroException)
        {
            displayValue = 0;
            txtDisplay.Text = "Cannot divide by zero.";
            newValue = true;
            decimalEntered = false;
        }
    }

}
}

然后是我类的一个样本(为了节省空间和时间，我只会做我的一个操作数)

 namespace Calculator
{
public class Calculator
{

    public Decimal displayValue;
    public Decimal currentValue;
    public Decimal firstNumber;
    public Decimal secondNumber;

     public decimal Add(Decimal displayValue)
    {

     return displayValue + currentValue;

    }

然后我假设因为没有 currentValue 并且它来 self 假设它是引用 displayValue 的类？虽然我不确定这是否会回到用户刚刚输入的内容，或者它是否会基本上重复？ (如果这是有道理的……但我的意思是你可以看出我对这部分有多困惑)。

所以真的是的，我只是在找人来解释它，如果我理解正确并朝着正确的方向前进，请告诉我......否则我想我搞砸了......

提前致谢。

Answer 1

您必须将结果存储在 current Value 变量中，因为稍后会在代码中使用它。此外，计算器方法的使用表明它们不应返回任何值。

public void Add(Decimal displayValue) 
{ 
    currentValue += display Value;
}

这样做的原因是 btnAdd_Click 中的以下行:

displayValue = calc.CurrentValue;

它期望 CurrentValue 属性保存当前值。