using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace 工廠方法實現計算器{  /// <summary>  /// 計算器類（抽象類，由子類重寫）  /// </summary>  public abstract class Calculator  {    public double Number1 { get; set; }    public double Number2 { get; set; }    public Calculator() { }    public Calculator(double a, double b)    {      this.Number1=a;      this.Number2=b;    }    /// <summary>    /// 計算    /// </summary>    /// <returns></returns>    public abstract double jsuan();  }  /// <summary>  /// 加法類  /// </summary>  public class jiafaDll:Calculator //子類擁有父類除私有之外的所有屬性字段和方法  {    public jiafaDll() { }    public jiafaDll(double a, double b)      : base(a, b)  //調用父類帶兩個參數的構造函數，來初始化Number1 和Number2 （注意：因為jianfaDll類繼承了Calculator，所以jianfaDll類是有Number1，和Number2兩個屬性的）    { }    /// <summary>    /// 重寫父類的jsuan方法    /// </summary>    /// <returns></returns>    public override double jsuan()    {      return Number1 + Number2;    }  }  /// <summary>  /// 減法類  /// </summary>  public class jianfaDll : Calculator  {    public jianfaDll()    { }    public jianfaDll(double a, double b)      : base(a, b)    { }    public override double jsuan()    {      return Number1 - Number2;    }  }  class Program  {    static void Main(string[] args)    {      Console.WriteLine("請輸入第一個數");      double number1 = Convert.ToDouble(Console.ReadLine());      Console.WriteLine("請輸入一個操作符");      string caozuofu = Console.ReadLine();      Console.WriteLine("請輸入第二個數");      double number2 = Convert.ToDouble(Console.ReadLine());      Calculator c=null;      switch (caozuofu)      {        case "+":          c = new jiafaDll(number1, number2);          break;        case "-":          c = new jianfaDll(number1, number2);          break;      }      double i= c.jsuan();      Console.WriteLine(i);      Console.ReadKey();    }  }}