C# 为什么我的计算器里的计算不正确？

对于我的C#类，我们需要编写一个简单的计算器来执行基本的数学运算（加、减、乘、除）。我看了教授的视频，他的节目很好。减法命令似乎在结果前面加了一个-。divide命令的结果有点不对劲。我做错了什么

例如：

123+2 = 125 (as it should)
123 - 2 = -121
124 / 2 = 0.0161290322580645
12.4 * 10 = 124 (correct)

这是我的密码：

public partial class Form1 : Form
    {
        string operand = "", operation = "", memory = "";
        public Form1()
        {
            InitializeComponent();
        }

        private void btnNum1_Click(object sender, EventArgs e)
        {
            txtOutput.Text += "1";
        }

        private void btnNum2_Click(object sender, EventArgs e)
        {
            txtOutput.Text += "2";
        }

        private void btnNum3_Click(object sender, EventArgs e)
        {
            txtOutput.Text += "3";
        }

        private void btnNum4_Click(object sender, EventArgs e)
        {
            txtOutput.Text += "4";
        }

        private void btnNum5_Click(object sender, EventArgs e)
        {
            txtOutput.Text += "5";
        }

        private void btnNum6_Click(object sender, EventArgs e)
        {
            txtOutput.Text += "6";
        }

        private void btnNum7_Click(object sender, EventArgs e)
        {
            txtOutput.Text += "7";
        }

        private void btnNum8_Click(object sender, EventArgs e)
        {
            txtOutput.Text += "8";
        }

        private void btnNum9_Click(object sender, EventArgs e)
        {
            txtOutput.Text += "9";
        }

        private void btnNum0_Click(object sender, EventArgs e)
        {
            txtOutput.Text += "0";
        }

        private void btnDec_Click(object sender, EventArgs e)
        {
            if (txtOutput.Text.IndexOf(".") == -1)
            {

                txtOutput.Text += ".";

            }
        }

        private void btnNegPos_Click(object sender, EventArgs e)
        {
            if (txtOutput.Text.IndexOf("-") == -1)
            {
                txtOutput.Text = "-" + txtOutput.Text;
            }
            else
            {
                txtOutput.Text = txtOutput.Text.Substring(1, (txtOutput.Text.Length - 1));
            }
        }

        private void execute()
        {
            if (operation == "+")
            {
                operand = Convert.ToString(Convert.ToDouble(txtOutput.Text) + Convert.ToDouble(operand));
            }
            if (operation == "-")
            {
                operand = Convert.ToString(Convert.ToDouble(txtOutput.Text) - Convert.ToDouble(operand));
            }
            if (operation == "*")
            {
                operand = Convert.ToString(Convert.ToDouble(txtOutput.Text) * Convert.ToDouble(operand));
            }
            if (operation == "/")
            {
                operand = Convert.ToString(Convert.ToDouble(txtOutput.Text) / Convert.ToDouble(operand));
            }
        }

        private void btnAdd_Click(object sender, EventArgs e)
        {
            if (operand == "")
            {
                operand = txtOutput.Text;
            }
            else
            {
                execute();
            }
            operation = "+";
            txtOutput.Text = "";
        }

        private void btnSubtract_Click(object sender, EventArgs e)
        {
            if (operand == "")
            {
                operand = txtOutput.Text;
            }
            else
            {
                execute();
            }
            operation = "-";
            txtOutput.Text = "";
        }

        private void btnMultiply_Click(object sender, EventArgs e)
        {
            if (operand == "")
            {
                operand = txtOutput.Text;
            }
            else
            {
                execute();
            }
            operation = "*";
            txtOutput.Text = "";
        }

        private void btnDivide_Click(object sender, EventArgs e)
        {
            if (operand == "")
            {
                operand = txtOutput.Text;
            }
            else
            {
                execute();
            }
            operation = "/";
            txtOutput.Text = "";
        }

        private void btnClear_Click(object sender, EventArgs e)
        {
            txtOutput.Text = "";
            operand = "";
            operation = "";
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void btnEquals_Click(object sender, EventArgs e)
        {
            if (operation == "+")
            {
                txtOutput.Text = Convert.ToString(Convert.ToDouble(txtOutput.Text) + Convert.ToDouble(operand));
            }
            if (operation == "-")
            {
                txtOutput.Text = Convert.ToString(Convert.ToDouble(txtOutput.Text) - Convert.ToDouble(operand));
            }
            if (operation == "*")
            {
                txtOutput.Text = Convert.ToString(Convert.ToDouble(txtOutput.Text) * Convert.ToDouble(operand));
            }
            if (operation == "/")
            {
                txtOutput.Text = Convert.ToString(Convert.ToDouble(txtOutput.Text) / Convert.ToDouble(operand));
            }
            operand = "";
            operation = "";
        }

        private void btnBackspace_Click(object sender, EventArgs e)
        {
            txtOutput.Text = "";
        }
    }

---

谢谢您的时间。

您已经得到了 2/124=0.0161290322580645

---

反转您的股息和除数；）

您正在反向操作您的参数。在等分函数中，第二个算符除以第一个算符，得到分数。在减法中，你做的是2-123，得到的是一个负数，例如，改为

 txtOutput.Text = Convert.ToString( Convert.ToDouble(operand) / Convert.ToDouble(txtOutput.Text));

---

我并没有真正为代码操心，但这里有一个提示：2/124=0.0161290322580645我认为学习调试比简单地在StackOverflow上发布代码并询问它有什么问题要好得多。如果设置了断点，应该清楚为什么操作没有产生预期的结果。这将导致编译器错误，不能将“double”除以“string”。需要将

Convert.ToString

移到计算之外。@RonBeyer您是对的，先生，我复制/粘贴得太匆忙了。我已经修好了。毫无疑问，减法也有同样的问题。