温故而知新:设计模式之Builder

#region  把不依赖具体细节的部分（即相当稳定，不变的部分）抽象出来
     public   interface  IShow
    {
         void  Show();
    }


     ///   <summary>
     ///  页面头部 抽象类
     ///   </summary>
     public   abstract   class  Header : IShow
    {
         public   abstract   void  Show();
    }

     ///   <summary>
     ///  页面主体 抽象类
     ///   </summary>
     public   abstract   class  Body : IShow
    {
         public   abstract   void  Show();
    }

     ///   <summary>
     ///  页面底部 抽象类
     ///   </summary>
     public   abstract   class  Footer : IShow
    {
         public   abstract   void  Show();
    }

     ///   <summary>
     ///  页面基类 抽象类
     ///   </summary>
     public   class  MainPage
    {
         private  List < IShow >  _lstParts;

         public  List < IShow >  Parts
        {
             set  { _lstParts  =  value; }
             get
            {
                 if  (_lstParts  ==   null )
                {
                    _lstParts  =   new  List < IShow > ();
                }
                 return  _lstParts;
            }
        }

         public   void  Show()
        {
             for  ( int  i  =   0 ; i  <  _lstParts.Count; i ++ )
            {
                _lstParts[i].Show();
            }
            Console.Write( " 页面构建完毕! " );
        }


    }

     ///   <summary>
     ///  创建器 抽象类
     ///   </summary>
     public   abstract   class  Builder
    {
         // 不管页面风格如何变换，下面的这些部件的创建算法，相对要求比较稳定

         public   abstract   void  BuildHeader();

         public   abstract   void  BuildBody();

         public   abstract   void  BuildFooter();

         public   abstract  MainPage GetPage();

    }
     #endregion

///   <summary>
     ///  客户程序
     ///   </summary>
     public   class  PageManager
    {
        Builder _builder;

         public  PageManager(Builder b)
        {
             this ._builder  =  b;
        }

         public   void  Show()
        {
             this ._builder.BuildHeader();
             this ._builder.BuildBody();
             this ._builder.BuildFooter();
             this ._builder.GetPage().Show();
        }
    }

#region  spring风格的具体页面及创建器
     public   class  SpringHeader : Header
    {
         public   override   void  Show()
        {
            Console.WriteLine( " Spring风格的header " );
        }
    }

     public   class  SpringBody : Body
    {
         public   override   void  Show()
        {
            Console.WriteLine( " Spring风格的body " );
        }
    }

     public   class  SpringFooter : Footer
    {
         public   override   void  Show()
        {
            Console.WriteLine( " Spring风格的footer " );
        }
    }

     public   class  SpringBuilder : Builder
    {
        MainPage _mainPage;

         public  SpringBuilder()
        {
            _mainPage  =   new  MainPage();
        }

         public   override   void  BuildHeader()
        {
            _mainPage.Parts.Add( new  SpringHeader());
        }

         public   override   void  BuildBody()
        {
            _mainPage.Parts.Add( new  SpringBody());
        }

         public   override   void  BuildFooter()
        {
            _mainPage.Parts.Add( new  SpringFooter());
        }

         public   override  MainPage GetPage()
        {
             return  _mainPage;
        }


    }
     #endregion


     #region  summer风格的具体页面及创建器
     public   class  SummerHeader : Header
    {
         public   override   void  Show()
        {
            Console.WriteLine( " Summer风格的header " );
        }
    }

     public   class  SummerBody : Body
    {
         public   override   void  Show()
        {
            Console.WriteLine( " Summer风格的body " );
        }
    }

     public   class  SummerFooter : Footer
    {
         public   override   void  Show()
        {
            Console.WriteLine( " Summer风格的footer " );
        }
    }

     public   class  SummerBuilder : Builder
    {
        MainPage _mainPage;

         public  SummerBuilder()
        {
            _mainPage  =   new  MainPage();
        }

         public   override   void  BuildHeader()
        {
            _mainPage.Parts.Add( new  SummerHeader());
        }

         public   override   void  BuildBody()
        {
            _mainPage.Parts.Add( new  SummerBody());
        }

         public   override   void  BuildFooter()
        {
            _mainPage.Parts.Add( new  SummerFooter());
        }

         public   override  MainPage GetPage()
        {
             return  _mainPage;
        }


    }
     #endregion

<? xml version="1.0" encoding="utf-8"  ?>
< configuration >
   < appSettings >
     < add  key ="AssemblyName"  value ="Builder" />
     < add  key ="BuilderType"  value ="Builder.SpringBuilder" />
   </ appSettings >
</ configuration >

using  System;
using  System.Collections.Generic;
using  System.Reflection;
using  System.Configuration;

namespace  Builder
{
     class  Program
    {
         static   void  Main( string [] args)
        {
            Builder bdr  =  (Builder)Assembly.Load(ConfigurationManager.AppSettings[ " AssemblyName " ].ToString()).CreateInstance(ConfigurationManager.AppSettings[ " BuilderType " ].ToString());
            PageManager pm  =   new  PageManager(bdr);
            pm.Show();
            Console.Read();
        }
    }

}