C#如何使用带开关的枚举

问题描述 投票:60回答:10

我无法弄清楚如何将开关与枚举结合使用。你能告诉我我做错了什么,以及如何解决它?我必须使用枚举来制作基本的计算器。

public enum Operator
{
    PLUS, MINUS, MULTIPLY, DIVIDE
}

public double Calculate(int left, int right, Operator op)
{

    int i = (int) op;

    switch(i)
    {
        case 0:
        {
            return left + right;
        }

        case 1:
        {
            return left - right;
        }

        case 2:
        { 
            return left * right;
        }

        case 3:
        {
            return left / right;
        }

        default:
        {
            return 0.0;
        }
    }
}

最终结果应该是这样的:

Console.WriteLine("The sum of 5 and 5 is " + Calculate(5, 5, PLUS))
Output: The sum of 5 and 5 is 10

你能告诉我我是怎么弄乱的吗?

c# enums switch-statement
10个回答
97
投票

你不需要转换它

switch(op)
{
     case Operator.PLUS:
     {
        // your code 
        // for plus operator
        break;
     }
     case Operator.MULTIPLY:
     {
        // your code 
        // for MULTIPLY operator
        break;
     }
     default: break;
}

顺便说一句,使用括号


0
投票

无需转换。您可以在交换机内的Enum上应用条件。像这样,

public enum Operator
{ 
    PLUS,
    MINUS,
    MULTIPLY,
    DIVIDE
}

public double Calculate(int left, int right, Operator op)
{
    switch (op)
    {
        case Operator.PLUS: return left + right; 
        case Operator.MINUS: return left - right; 
        case Operator.MULTIPLY: return left * right;
        case Operator.DIVIDE: return left / right;
        default: return 0.0; 
    }
}

然后,这样称呼它:

Console.WriteLine("The sum of 5 and 5 is " + Calculate(5, 5, Operator.PLUS));

9
投票

已经给出了正确的答案,不过这里有更好的方法(比开关):

private Dictionary<Operator, Func<int, int, double>> operators =
    new Dictionary<Operator, Func<int, int, double>>
    {
        { Operator.PLUS, ( a, b ) => a + b },
        { Operator.MINUS, ( a, b ) => a - b },
        { Operator.MULTIPLY, ( a, b ) => a * b },
        { Operator.DIVIDE ( a, b ) => (double)a / b },
    };

public double Calculate( int left, int right, Operator op )
{
    return operators.ContainsKey( op ) ? operators[ op ]( left, right ) : 0.0;
}

4
投票

根本就不要转换为int

 switch(operator)
    {
       case Operator.Plus:
       //todo

2
投票

你不应该转换为整数。对于除法,你需要先左转加倍,否则你会做一个整数除法。

public enum Operator
{
    PLUS, MINUS, MULTIPLY, DIVIDE
}

public double Calculate(int left, int right, Operator op)
{
    double sum = 0.0;

    switch(op)
    {
       case Operator.PLUS:
       sum = left + right;
       return sum;

       case Operator.MINUS:
       sum = left - right;
       return sum;

       case Operator.MULTIPLY:
       sum = left * right;
       return sum;

       case Operator.DIVIDE:
       sum = (double)left / right;
       return sum;

       default:
       return sum;
   }

   return sum;
}

2
投票
 public enum Operator
    {
        PLUS, MINUS, MULTIPLY, DIVIDE
    }

    public class Calc
    {
        public void Calculate(int left, int right, Operator op)
        {

            switch (op)
            {
                case Operator.DIVIDE:
                    //Divide
                    break;
                case Operator.MINUS:
                    //Minus
                    break;
                case Operator.MULTIPLY:
                    //...
                    break;
                case Operator.PLUS:
                    //;;
                    break;
                default:
                    throw new InvalidOperationException("Couldn't process operation: " + op);
            }
        }
    }

1
投票

如果您不想对每种情况使用return语句,请尝试以下操作:

Calculate(int left, int right, Operator op)
{
   int result = 0;
   switch(op)
   {
        case Operator.PLUS:
        {
            result = left + right;;  
        }
        break;
        ....
   }

   return result;
}

1
投票

所有其他答案都是正确的,但您还需要正确调用您的方法:

Calculate(5, 5, Operator.PLUS))

而且因为你使用int用于leftright,结果将是int3/2 will result in 1)。您可以在计算结果之前强制转换为double或修改您的参数以接受double


0
投票

两件事情。首先,您需要在测试中限定枚举引用 - 而不是“PLUS”,它应该是“Operator.PLUS”。其次,如果您使用枚举成员名称而不是switch语句中的整数值,则此代码将更具可读性。我已经更新了你的代码:

public enum Operator
{
    PLUS, MINUS, MULTIPLY, DIVIDE
}

public static double Calculate(int left, int right, Operator op)
{
    switch (op)
    {
        default:
        case Operator.PLUS:
            return left + right;

        case Operator.MINUS:
            return left - right;

        case Operator.MULTIPLY:
            return left * right;

        case Operator.DIVIDE:
            return left / right;
    }
}

称之为:

Console.WriteLine("The sum of 5 and 5 is " + Calculate(5, 5, Operator.PLUS));

0
投票

你的代码很好。如果您不确定如何使用计算功能,请尝试

Calculate(5,5,(Operator)0); //this will add 5,5
Calculate(5,5,Operator.PLUS);// alternate

默认枚举值从0开始,对于后续元素增加1,直到您指定不同的值。你也可以这样做:

public enum Operator{PLUS=21,MINUS=345,MULTIPLY=98,DIVIDE=100};
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