C＃中的if / else条件

Question

我最近开始进行“编码”，我真的很开始，这是我的第一个“项目”。 它应该是SI转换器，您可以在其中键入值，其单位和要转换的单位。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Program
{
    class Program
    {
        static void Main()
        {
            decimal one = 1;
            decimal two = 0.001m;
            decimal three = 0.000001m;
            decimal four = 0.000000001m;
            decimal five = 0.000000000001m;
            decimal answer;


       begn: Console.WriteLine("SI converter!\nPlease, enter value: ");             
            decimal value = Convert.ToInt32(Console.ReadLine());

            Console.WriteLine("\nFactors: \n1.One \n2.Milli(m)\n3.Micro(µ)\n4.Nano(n)\n5.Pico(p)\nEnter factor: "); 
            decimal factor = int.Parse(Console.ReadLine());

            if (factor == 1)
            {
                factor = one;
            }else if (factor == 2)
            {
                factor = two;
            }else if (factor == 3)
            {
                factor = three;
            }else if (factor == 4)
            {
                factor = four;
            }else if (factor == 5)
            {
                factor = five;
            }


            Console.WriteLine("\nFactors: \n1.One \n2.Milli(m)\n3.Micro(µ)\n4.Nano(n)\n5.Pico(p)\nEnter the second factor: ");
            decimal factor2 = Convert.ToInt32(Console.ReadLine());

            if (factor2 == 1)
            {
                factor2 = one;
                answer = value * factor;
                Console.WriteLine("The answer is : " + answer);
            }
            else if (factor2 == 2)
            {
                factor2 = two;
            }
            else if (factor2 == 3)
            {
                factor2 = three;
            }
            else if (factor2 == 4)
            {
                factor2 = four;
            }
            else if (factor2 == 5)
            {
                factor2 = five;
            }



                answer = value * factor / factor2;                      
                Console.WriteLine("The answer is : " + answer);


            Console.WriteLine("Go again?\nY / N");          
            char ans =char.Parse(Console.ReadLine());
            if (ans == 'y')
            {
                Console.Clear();
                goto begn;

            }
            if(ans=='n')
            {

                Console.ReadKey();
            }


        }


        }
    }

所以问题是我不太喜欢这部分，也不知道如何去做：

 if (factor == 1)
            {
                factor = one;
            }else if (factor == 2)
            {
                factor = two;
            }else if (factor == 3)
            {
                factor = three;
            }else if (factor == 4)
            {
                factor = four;
            }else if (factor == 5)
            {
                factor = five;
            }

PS是的，我知道它可能真的很糟糕，但这是我的第一次尝试。如果您能给我任何提示，我会很高兴的:)

Answer 1

使用开关条件

switch (factor)
         {
            case 1:
               factor = one;
               break;
            case 2:
               factor = two;
               break;
            case 3:
               factor = three;
               break;
            case 4:
                factor = four;
               break;
               default:
                //default when nothing happens in switch
                factor = one;
               break;
         }

Answer 2

using System;

namespace Program
{
    class Program
    {
        static decimal[,] factors = new decimal[4, 4] {
            /*               To Milli        To Micro    To Nano,  To Pico    */
            /* From Milli */ { 1m,           1000m,      1000000m, 1000000000m },
            /* From Micro */ { 0.001m,       1m,         1000m,    1000000m    },
            /* From Nano  */ { 0.000001m,    0.001m,     1m,       1000m       },
            /* From Pico  */ { 0.000000001m, 0.000001m,  0.001m,   1m          }
        };

        static void Main()
        {
            Console.WriteLine("SI converter!");

            while(true)
            {
                Console.Write("Please, enter value: ");
                decimal value = Convert.ToInt32(Console.ReadLine());

                Console.Write("\n1) Milli(m)\n2) Micro(µ)\n3) Nano(n)\n4) Pico(p)\nFrom Units: ");
                int fromUnits = int.Parse(Console.ReadLine()) - 1;

                Console.Write("To Units: ");
                int toUnits = int.Parse(Console.ReadLine()) - 1;

                decimal factor = factors[fromUnits, toUnits];
                decimal answer = factor * value;
                Console.WriteLine("The answer is : " + answer);

                Console.Write("Go again? (Y/N): ");    
                string ans = Console.ReadLine();

                if(ans.ToUpper() == "N")
                    break;
            }
        }
    }
}

Answer 3

您可以通过创建具有不同值及其适当文本的数组来更动态地执行此操作。 然后只需使用数组列的值打印相关文本。

string[] arrayText = { "one", "two", "three", "four", "five"};
//Remember than your array start at 0
factor= factor - 1;
System.console.WriteLine(arrayText[factor]);

我认为这就是您想要的！

Answer 4

代替if/else块，可以使用Dictionary<string, decimal> ，其中key （字符串）是期望的输入， value （十进制）是输入所对应的变量。

应用启动时，您可以使用单独的方法构建此词典，因为这些值不会更改。 使字典可用于程序的其余部分（例如，使用public ），并且可以通过相同的简单检查在需要的任何地方重用此信息。

一旦字典建成后，所有你所要做的就是检查词典包含输入值和设定factor1 （或factor2 ）因此：

 string input;
 decimal factor1;

 Dictionary<string, decimal> factors = new Dictionary<string, decimal>();

 factors.Add("1", one);
 factors.Add("2", two);
 factors.Add("3", three);
 factors.Add("4", four);
 factors.Add("5", five);

 input = Console.ReadLine();

 if (factors.ContainsKey(input))
 {
    factor1 = factors["input"];
 }

您还应该考虑按照you screwed up, try again在else地方添加else条件you screwed up, try again提示用户重新输入值。

另外，在您当前的代码中，请勿将factor变量用于输入和计算。 只需将输入作为字符串并检查特定值即可。

为了获得更多帮助，我建议按照评论中的建议使用CodeReview。

Answer 5

您可以使用类似于以下代码：

decimal answer;
decimal[] factorArray = new decimal[] { 1, 0.001m, 0.000001m, 0.000000001m, 0.000000000001m };

Console.WriteLine("SI converter!\nPlease, enter value: ");
decimal value = Convert.ToInt32(Console.ReadLine());

Console.WriteLine("\nFactors: \n1.One \n2.Milli(m)\n3.Micro(µ)\n4.Nano(n)\n5.Pico(p)\nEnter factor: ");
decimal factor = int.Parse(Console.ReadLine());
if (factor >= 1 && factor <= factorArray.Length)
{
    factor = factorArray[(int)factor - 1];
}

Console.WriteLine("\nFactors: \n1.One \n2.Milli(m)\n3.Micro(µ)\n4.Nano(n)\n5.Pico(p)\nEnter the second factor: ");
decimal factor2 = Convert.ToInt32(Console.ReadLine());
if (factor2 >= 1 && factor2 <= factorArray.Length)
{
    factor2 = factorArray[(int)factor2 - 1];
}