C＃计算器在某些操作Windows窗体应用程序中使用列表数组错误

Question

Hello I'm still new to programming and yes this is not the best code you will see... I tried making calculator on C# windows form for fun and I'm having trouble on the subtraction and division operations, but the addition and multiplication works perfectly fine for me. I decided to have a list array so that I would be able to input numbers as much as I want.

The error for the subtraction is when I input for example 5 - 2 the result will be -3

As for the division the error is that the result is always 1

Please tell me where did I go wrong and give a detailed explanation if possible so that I would understand more about programming. Thanks in advance!

namespace CalculatorTestForm1
{
public partial class Form1 : Form
{
    public static List<int> Numlist = new List<int>();
    public static string operation;

    public Form1()
    {
        InitializeComponent();
    }

    private void Button_Click(object sender, EventArgs e)
    {
        Button Num = (Button)sender;
        TXTBox.Text += Num.Text;
    }

    private void BPlus_Click(object sender, EventArgs e)
    {
        operation = "add";
        int AddNum = Convert.ToInt32(this.TXTBox.Text);
        Numlist.Add(AddNum);
        TXTBox.Text = "";          
    }

    private void BEquals_Click(object sender, EventArgs e)
    {       
        int AddNum = Convert.ToInt32(this.TXTBox.Text);
        Numlist.Add(AddNum);

        int sum = 0;
        int product = 1;
        int quotient = 1;
        int difference = 0;

        if (operation == "add"){
            foreach (int value in Numlist)
            {
                sum += value;
            }
            string Answer = sum.ToString();
            TXTBox.Text = Answer;    
        }else if(operation == "minus"){
            foreach (int value in Numlist)
            {
                difference = value - difference;
            }
            string Answer = difference.ToString();
            TXTBox.Text = Answer;
        }
        else if (operation == "multiply")
        {
            foreach (int value in Numlist)
            {
                product *= value;
            }
            string Answer = product.ToString();
            TXTBox.Text = Answer;
        }
        else if (operation == "divide")
        {
            foreach (int value in Numlist)
            {
                quotient = value / value;
            }
            string Answer = quotient.ToString();
            TXTBox.Text = Answer;
        }
        Numlist.Clear();
    }

    private void BClear_Click(object sender, EventArgs e)
    {
        TXTBox.Text = "";
        Numlist.Clear();
    }

    private void BMinus_Click(object sender, EventArgs e)
    {
        operation = "minus";
        int AddNum = Convert.ToInt32(this.TXTBox.Text);
        Numlist.Add(AddNum);
        TXTBox.Text = "";         
    }

    private void BDivide_Click(object sender, EventArgs e)
    {
        operation = "divide";
        int AddNum = Convert.ToInt32(this.TXTBox.Text);
        Numlist.Add(AddNum);
        TXTBox.Text = "";  
    }

    private void BMulti_Click(object sender, EventArgs e)
    {
        operation = "multiply";
        int AddNum = Convert.ToInt32(this.TXTBox.Text);
        Numlist.Add(AddNum);
        TXTBox.Text = "";         
    }
  }
}

Answer 1

For the division it's obvious:

quotient = value / value;

value / value will always be 1 .

There must be quotient in that loop somewhere...

For the subtraction the problem is that because of the way you do it, the order of the numbers are reversed.

lets say 5 - 2:

foreach (int value in Numlist)
{
    difference = value - difference;
}

NumList = {5,2}

1st iteration: difference = value(5) - difference(0) = 5

2nd iteration: difference = value(2) - difference(5) = -3

You should reverse the order of the loop: NumList.Reverse()

And for the division as well:

Division:

foreach (int value in Numlist.Reverse())
{
    quotient = value / quotient;
}

Subtraction:

foreach (int value in Numlist)
{
    difference = value - difference;
}