Question

我需要将这些If语句转换为Switch-case语句。我这样做时会出现语法错误。我试过用smth。像：

switch(field.text){
case field.text.contains("+"):
field.text=a+b;
break;
}

但＆＃34; field.text.contains（＆＃34; +＆＃34;）＆＃34;有语法错误。

我需要帮助。这是我的代码：

这是计算器应用程序，执行简单的2运算符数学运算。

这是将字符串拆分为2以便找到2个输入数字的方法：

public void GetNumbers(ref string first, ref string second, int place, out int firstNumber, out int secondNumber)
{
    if (place > 0)
    {
        first = ResultFiled.Text.Substring(0, place);

        second = ResultFiled.Text.Substring(place + 1);
    }

    Int32.TryParse(first, out firstNumber);
    Int32.TryParse(second, out secondNumber);
}

private void Calculate_Click(object sender, EventArgs e)
{

    string first = null;
    string second = null;
    int result = 0;
    int place = 0;
    int firstNumber = 0;
    int secondNumber = 0;

在计算器表单中标识输入数字中的运算符，然后找到它的位置。将字符串拆分为2，以查找第一个和最后一个数字。然后做数学运算。

添加2个数字

    if (ResultFiled.Text.Contains("+"))
    {
        place = ResultFiled.Text.IndexOf("+");

        GetNumbers(ref first, ref second, place, out firstNumber, out secondNumber);

        result = firstNumber + secondNumber;

        ResultFiled.Text = result.ToString();
    }

    else
    {

减去2个数字

        if (ResultFiled.Text.Contains("-"))    
        {
            place = ResultFiled.Text.IndexOf("-");
            GetNumbers(ref first, ref second, place, out firstNumber, out secondNumber);

            result = firstNumber - secondNumber;

            ResultFiled.Text = Convert.ToString(result);
        }

    else
    {

乘以2个数字

        if (ResultFiled.Text.Contains("*"))
        {
            place = ResultFiled.Text.IndexOf("*");
            GetNumbers(ref first, ref second, place, out firstNumber, out secondNumber);

            result = firstNumber * secondNumber;

            ResultFiled.Text = Convert.ToString(result);
        }

        else
        {

除以2个数字

            if (ResultFiled.Text.Contains("/"))
            {
                place = ResultFiled.Text.IndexOf("/");
                GetNumbers(ref first, ref second, place, out firstNumber, out secondNumber);

                try
                {
                    result = firstNumber / secondNumber;
                }
                catch (DivideByZeroException exc)
                {
                    MessageBox.Show(exc.Message);
                }

                ResultFiled.Text = Convert.ToString(result);
            }
         }
      }
   }
 }

Answer 1

首先创建枚举MathOp：

  enum MathOp {Null, Add, Sub, Mult, Div }

然后：

  var op = 
     txt.Contains("+")? MathOp.Add:
     txt.Contains("-")? MathOp.Sub:
     txt.Contains("*")? MathOp.Mult:
     txt.Contains("/")? MathOp.Div: 
                        MathOp.Null;

  switch (op)
  {
      case (MathOp.Add):
         ...

      case (MathOp.Sub):
         ...

  }

Answer 2

如果您也拆分了运算符（+， - 等），您可以执行类似以下操作：

public enum Operator {
    Plus,
    Minus
}

Operator operator = Operator.Plus; // As an example.

switch (operator) {
    case Operator.Plus:
        Console.WriteLine("Here's the plus operator");
        break;
    case Operator.Minus:
        Console.WriteLine("Here's the minus operator");
        break;
    default:
        Console.WriteLine("This isn't an operator");
        break;

然后，在发生Console.WriteLine的操作发生时替换您要运行的代码。这是一个很好的格式，分成函数：

public int PerformOperation(int firstNumber, int secondNumber, string operator) {
switch (operator) {
    case Operator.Plus:
        Console.WriteLine("Here's the plus operator");
        return (firstNumber + secondNumber);
        break;
    case Operator.Minus:
        return (firstNumber - secondNumber);
        break;
    default:
        Console.WriteLine("This isn't an operator");
        break;

然后，您可以按如下方式编写逻辑：

void SomeMainFunction() {
    string textBoxInput = txbInput.Text; // Example of fetching calc input

    int firstNumber = GetFirstNumber(textBoxInput); // Write a function that returns your firstNumber from the input string.
    int firstNumber = GetSecondNumber(textBoxInput); // Write a function that returns your secondNumber from the input string.
    string operator = GetOperator(textBoxInput); // Write a function that returns your operator from the input string.

    txbInput.Text = PerformOperation(firstNumber, secondNumber, operator);
}

如何将这些if语句转换为switch-case C＃

2 个答案: