实例解析C#设计模式编程中简单工厂模式的使用

/// <summary>
  /// 自己做饭的情况
  /// 没有简单工厂之前，客户想吃什么菜只能自己炒的
  /// </summary>
  public class Customer
  {
    /// <summary>
    /// 烧菜方法
    /// </summary>
    /// <param name="type"></param>
    /// <returns></returns>
    public static Food Cook(string type)
    {
      Food food = null;
      // 客户A说：我想吃西红柿炒蛋怎么办？
      // 客户B说：那你就自己烧啊
      // 客户A说： 好吧，那就自己做吧
      if (type.Equals("西红柿炒蛋"))
      {
        food = new TomatoScrambledEggs();
      }
      // 我又想吃土豆肉丝, 这个还是得自己做
      // 我觉得自己做好累哦，如果能有人帮我做就好了？
      else if (type.Equals("土豆肉丝"))
      {
        food = new ShreddedPorkWithPotatoes();
      }
      return food;
    }
    static void Main(string[] args)
    {
      // 做西红柿炒蛋
      Food food1 = Cook("西红柿炒蛋");
      food1.Print();
      Food food2 = Cook("土豆肉丝");
      food1.Print();
      Console.Read();
    }
  }
 /// <summary>
  /// 菜抽象类
  /// </summary>
  public abstract class Food
  {
    // 输出点了什么菜
    public abstract void Print();
  }
  /// <summary>
  /// 西红柿炒鸡蛋这道菜
  /// </summary>
  public class TomatoScrambledEggs : Food
  {
    public override void Print()
    {
      Console.WriteLine("一份西红柿炒蛋！");
    }
  }
  /// <summary>
  /// 土豆肉丝这道菜
  /// </summary>
  public class ShreddedPorkWithPotatoes : Food
  {
    public override void Print()
    {
      Console.WriteLine("一份土豆肉丝");
    }
  }

/// <summary>
  /// 顾客充当客户端，负责调用简单工厂来生产对象
  /// 即客户点菜，厨师（相当于简单工厂）负责烧菜(生产的对象)
  /// </summary>
  class Customer
  {
    static void Main(string[] args)
    {
      // 客户想点一个西红柿炒蛋   
      Food food1 = FoodSimpleFactory.CreateFood("西红柿炒蛋");
      food1.Print();
      // 客户想点一个土豆肉丝
      Food food2 = FoodSimpleFactory.CreateFood("土豆肉丝");
      food2.Print();
      Console.Read();
    }
  }
  /// <summary>
  /// 菜抽象类
  /// </summary>
  public abstract class Food
  {
    // 输出点了什么菜
    public abstract void Print();
  }
  /// <summary>
  /// 西红柿炒鸡蛋这道菜
  /// </summary>
  public class TomatoScrambledEggs : Food
  {
    public override void Print()
    {
      Console.WriteLine("一份西红柿炒蛋！");
    }
  }
  /// <summary>
  /// 土豆肉丝这道菜
  /// </summary>
  public class ShreddedPorkWithPotatoes : Food
  {
    public override void Print()
    {
      Console.WriteLine("一份土豆肉丝");
    }
  }
  /// <summary>
  /// 简单工厂类, 负责 炒菜
  /// </summary>
  public class FoodSimpleFactory
  {
    public static Food CreateFood(string type)
    {
      Food food = null;
      if (type.Equals("土豆肉丝"))
      {
        food= new ShreddedPorkWithPotatoes();
      }
      else if (type.Equals("西红柿炒蛋"))
      {
        food= new TomatoScrambledEggs();
      }
      return food;
    }
  }

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection;

namespace ConsoleApplication1
{
  public interface IFruit
  {
  }

  public class Orange : IFruit
  {
    public Orange()
    {
      Console.WriteLine("An orange is got!");
    }
  }

  public class Apple : IFruit
  {
    public Apple()
    {
      Console.WriteLine("An apple is got!");
    }
  }

  public class FruitFactory
  {
    private static FruitFactory _instance = new FruitFactory();
    public static FruitFactory Instance
    {
      get { return _instance; }
    }

    public IFruit MakeFruit(string Name)
    {
      IFruit MyFruit = null;
      try
      {
        Type type = Type.GetType(Name, true);
        MyFruit = (IFruit)Activator.CreateInstance(type);
      }
      catch (TypeLoadException e)
      {
        Console.WriteLine("I dont know this kind of fruit,exception caught - {0}", e.Message);
      }
      return MyFruit;
    }
  }

  public class Test
  {
    static void Main()
    {
      string FruitName = Console.ReadLine();
      FruitFactory.Instance.MakeFruit("ConsoleApplication1." + FruitName);
    }
  }
}

public static Encoding GetEncoding(int codepage)
{
  Encoding unicode = null;
  if (encodings != null)
  {
    unicode = (Encoding) encodings[codepage];
  }
  if (unicode == null)
  {
    object obj2;
    bool lockTaken = false;
    try
    {
      Monitor.Enter(obj2 = InternalSyncObject, ref lockTaken);
      if (encodings == null)
      {
        encodings = new Hashtable();
      }
      unicode = (Encoding) encodings[codepage];
      if (unicode != null)
      {
        return unicode;
      }
      switch (codepage)
      {
        case 0:
          unicode = Default;
          break;
        case 1:
        case 2:
        case 3:
        case 0x2a:
          throw new ArgumentException(Environment.GetResourceString("Argument_CodepageNotSupported", new object[] { codepage }), "codepage");
        case 0x4b0:
          unicode = Unicode;
          break;
        case 0x4b1:
          unicode = BigEndianUnicode;
          break;
        case 0x6faf:
          unicode = Latin1;
          break;
        case 0xfde9:
          unicode = UTF8;
          break;
        case 0x4e4:
          unicode = new SBCSCodePageEncoding(codepage);
          break;
        case 0x4e9f:
          unicode = ASCII;
          break;
        default:
          unicode = GetEncodingCodePage(codepage);
          if (unicode == null)
          {
            unicode = GetEncodingRare(codepage);
          }
          break;
      }
      encodings.Add(codepage, unicode);
      return unicode;
    }
}

switch (codepage)
   {
     .......
  default:
          unicode = GetEncodingCodePage(codepage);
          if (unicode == null)
          {
            unicode = GetEncodingRare(codepage); //当编码很少见时
          }
          break;
      ......
   }