Question

我正在尝试使用类似于计算器的C＃制作表单。

我必须编写一个名为IsOperator的方法，该方法检查传递给它的文本框是否包含+，-，*或/值。

由于某种原因，它无法正确验证。

我尝试更改||到&&并将返回的结果反转为false和true，但没有任何效果。

当我尝试在运算符文本框中放入不是+ /-*的其他内容时，结果将变为0。没有任何结果可以验证。

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.Threading.Tasks;
using System.Windows.Forms;

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

        private void btnCalc_Click(object sender, EventArgs e)
        {
            try
            {
                if (IsValidData())
                {
                    MessageBox.Show("Error");
                } 
                else
                {
                    decimal operand1 = Convert.ToDecimal(txtOperand1.Text);
                    string operator1 = txtOperator.Text;
                    decimal operand2 = Convert.ToDecimal(txtOperand2.Text);

                    decimal result = 0;
                    if (operator1 == "+")
                        result = operand1 + operand2;
                    else if (operator1 == "-")
                        result = operand1 - operand2;
                    else if (operator1 == "*")
                        result = operand1 * operand2;
                    else if (operator1 == "/")
                        result = operand1 / operand2;

                    result = Math.Round(result, 4);
                    txtResult.Text = result.ToString();
                    txtOperand1.Focus();
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message + "\n\n" +
                ex.GetType().ToString() + "\n" +
                ex.StackTrace, "Exception");
            }
        }

        public bool IsValidData()
        {
            return
             //validate the operand1 text box
             IsPresent(txtOperand1, "Operand 1") &&
             IsDecimal(txtOperand1, "Operand 1") &&
             IsWithinRange(txtOperand1, "Operand 1", 0, 1000000) &&

             //validates the operator text box
             IsPresent(txtOperator, "Operator") &&
             IsOperator(txtOperator, "Operator") &&

             //validates the operand 2 text box
             IsPresent(txtOperand2, "Operand 2") &&
             IsDecimal(txtOperand2, "Operand 2") &&
             IsWithinRange(txtOperand2, "Operand 2", 0, 1000000);
        }

        private void btnExit_Click(object sender, System.EventArgs e)
        {
            this.Close();
        }

        //is present
        public bool IsPresent(TextBox textBox, string name)
        {
            if (textBox.Text == "")
            {
                MessageBox.Show(name + " is a required field.", "Entry Error");
                textBox.Focus();
            }
            return false;
        }

        //is decimal
        public bool IsDecimal(TextBox textBox, string name)
        {
            decimal number = 0m;

            if (Decimal.TryParse(textBox.Text, out number))
            {
                return true;
            }
            else
            {
                MessageBox.Show(name + " must be a decimal value.", "Entry Error");
                textBox.Focus();
                return false;
            }
        }

        //is within range
        public bool IsWithinRange(TextBox textBox, string name, decimal min, decimal max)
        {
            decimal number = Convert.ToDecimal(textBox.Text);
            if (number < min || number > max)
            {
                MessageBox.Show(name + "must be between" + min.ToString()
                    + "and" + max.ToString() + ".", "Entry Error");
                textBox.Focus();
                return false;
            }
            return true;
        }

        //is a valid operator
        public bool IsOperator(TextBox textBox, string name)
        {
            string operator1 = "";
            operator1 = Convert.ToString(textBox.Text);
            if (operator1 == "+" && operator1 == "-" && operator1 == "/" && operator1 == "*")
            {
                MessageBox.Show("Please enter a valid operator in the operator text box.", "Entry Error");
                return false;
            }
            return true;
        }

        private void txtOperand1_TextChanged(object sender, EventArgs e)
        {
            this.txtResult.Text = "";
        }

        private void txtOperator_TextChanged(object sender, EventArgs e)
        {
            this.txtResult.Text = "";
        }

        private void txtOperand2_TextChanged(object sender, EventArgs e)
        {
            this.txtResult.Text = "";
        }
    }
}

Answer 1

所有拳头都不应该使用someString == ""或string.IsNullOrEmpty(someString)或string.IsEmptyOrWhitespace(someString)。 1

然后IsPresent总是返回false。您可以将该方法更改为

public bool IsPresent(TextBox textBox, string name)
{
    if (!string.IsNullOrEmpty(textBox.Text))
    {
         return true;
    }
    MessageBox.Show(name + " is a required field.", "Entry Error");
    textBox.Focus();

    return false;
}

在EventHandler中，您在!之前忘记了IsValidData()。当数据有效时，您将显示错误；当数据有故障时，您将尝试执行计算。

您的IsOperator方法实际上包含一个逻辑问题。如果运算符是以下任何字符+, -, *, \，则要返回true。因此，使用LINQ将if逻辑翻转为类似的东西比较容易

//is a valid operator
public bool IsOperator(TextBox textBox, string name)
{
    string operator = textBox.Text;
    if (new[] {"+", "-", "*", "/"}.Contains(operator))
    {
         return true;
    }

    MessageBox.Show("Please enter a valid operator in the operator text box.", "Entry Error");

    return false; 
}

我认为您的代码也可以从使用异常中受益，而不是在发生错误时立即显示MessageBoxes。

C＃简单计算器表单无法验证正确的运算符？

1 个答案: