public abstract class Calculator
 {
  public abstract int Operate(int a,int b);
 }

 public class Minus: Calculator
 {
  public override int Operate(int a, int b)
  {
   return a- b;
  }
 }

 public class Plus : Calculator
 {
  public override int Operate(int a, int b)
  {
   return a + b;
  }
 }

 public class Multiply : Calculator
 {
  public override int Operate(int a, int b)
  {
   return a * b;
  }
 }

 public class Divide : Calculator
 {
  public override int Operate(int a, int b)
  {
   if(b==0) throw new ArgumentException("除數(shù)不能為0");
   return a / b;
  }
 }

public class SimpleFactory
 {
  public Calculator GetOperation(string operatorName)
  {
   switch (operatorName)
   {
    case "Minus":
     return new Minus();

    case "Plus":
     return new Plus();

    case "Multiply":
     return new Multiply();

    case "Divide":
     return new Divide();

    default:
     throw new Exception("當(dāng)前未提供此計(jì)算方式");
   }
  }
 }

class Program
 {
  static void Main(string[] args)
  {
   SimpleFactory simpleFactory = new SimpleFactory();

   Dictionary<string,string> optionsDictionary = new Dictionary<string, string>
   {
    { "A","Plus"},
    { "B","Minus"},
    { "C","Multiply"},
    { "D","Divide"},
   };

   string readOptions = string.Empty;


   do
   {
    foreach (KeyValuePair<string, string> keyValuePair in optionsDictionary)
    {
     Console.WriteLine(keyValuePair.Key+"、"+keyValuePair.Value);
    }

    Console.WriteLine("請(qǐng)輸入A、B、C、D確定計(jì)算方式");
    string option = Console.ReadLine();
    if (!optionsDictionary.ContainsKey(option))
    {
     throw new Exception("當(dāng)前未提供此計(jì)算方式");
    }

    Console.WriteLine("請(qǐng)輸入第一個(gè)數(shù)");
    int a = Convert.ToInt32(Console.ReadLine());
    Console.WriteLine("請(qǐng)輸入第二個(gè)數(shù)");
    int b = Convert.ToInt32(Console.ReadLine());

    Calculator calculator = simpleFactory.GetOperation(optionsDictionary[option]);
    Console.WriteLine("當(dāng)前結(jié)果是："+calculator.Operate(a, b));

    Console.WriteLine("繼續(xù)請(qǐng)按Y");

    readOptions = Console.ReadLine();

   } while (readOptions == "Y");
  }
 }