自從有了html與http，就有了瀏覽器與Web服務器，并有了Web應用，最初的交互模式是這樣的：

??????該模式很好地運行了很多年。然而，隨著計算機應用的發展，人們越來越不滿足于只有靜態內容的頁面，而由某種機制動態產生html等代碼的需求越來越迫切，于是，很多技術就應運而生，Asp.net就是這樣一種技術。從本質上講，Asp.net就是一種服務器端動態產生html、css、javascript等瀏覽器認識的代碼的技術。Asp.net的交互模式如下：

?

??????由該圖可知，Asp.net必須解決兩大問題，一是如何與Web服務器（一般就是指IIS）進行交互，二是如何根據不同請求產生不同的html等代碼。

?

??????第一個問題，根據IIS版本（5.*，6.0，7.0）的不同，Asp.net具有不同的進程模式與不同的交互模式，該問題不是本篇要講述的。一般來說，大家不必關心該問題，而且要了解該問題，又必須清楚IIS各個版本的模型，而各個版本又各有各的不同，因此，我基本不準備講述這個問題，大家有興趣的話，可以自行搜索相關資料。

??????我們來討論第二個問題，這里首先要說明的是，因為IIS7.0進程模式的變化比較大，我也沒去了解IIS7.0的模型，因此，以下講述及以后講述將只針對IIS5.*與IIS6.0。我們有理由認為，針對IIS5.*與IIS6.0的講述一般同樣適用于IIS7.0。

??????先且按下該問題不表，我們來看一段請求玉帝把大象放到冰箱里的代碼（為什么不是上帝？因為我中華不歸上帝管），請大家先跟著我的思路來，別急，別急。

Code1
using?System;

namespace?ConsoleApplication3
{
????class?Program
????{
????????static?void?Main(string[]?args)
????????{
????????????Emperor?emperor?=?new?Emperor();
????????????while?(true)
????????????{
????????????????Console.WriteLine("首先給玉帝準備好大象和冰箱。");

????????????????Console.WriteLine("輸入大象的名字：");
????????????????string?elephantName?=?Console.ReadLine();
????????????????Console.WriteLine("輸入大象的體重：");
????????????????int?elephantWeight?=?int.Parse(Console.ReadLine());
????????????????Console.WriteLine("輸入冰箱的名字：");
????????????????string?refrigeratorName?=?Console.ReadLine();

????????????????Elephant?elephant?=?new?Elephant()
????????????????{
????????????????????Name?=?elephantName,
????????????????????Weight?=?elephantWeight
????????????????};
????????????????Refrigerator?refrigerator?=?new?Refrigerator()
????????????????{
????????????????????Name?=?refrigeratorName
????????????????};

????????????????Context?context?=?new?Context()
????????????????{
????????????????????Elephant?=?elephant,
????????????????????Refrigerator?=?refrigerator
????????????????};

????????????????emperor.ProcessRequest(context);

????????????????Console.WriteLine("是否要玉帝繼續把大象關進冰箱里？");
????????????????string?answer?=?Console.ReadLine();
????????????????if?(answer?==?"n")
????????????????????break;
????????????}
????????}
????}

????class?Emperor
????{
????????public?void?ProcessRequest(Context?context)
????????{
????????????Elephant?elephant?=?context.Elephant;
????????????Refrigerator?refrigerator?=?context.Refrigerator;

????????????//第一步，打開冰箱門
????????????refrigerator.IsOpen?=?true;
????????????Console.WriteLine(string.Format("玉帝打開了?{0}?的冰箱門。",?refrigerator.Name));

????????????//第二步，把大象放進去
????????????refrigerator.Content?=?elephant;
????????????Console.WriteLine(string.Format("玉帝把大象?{0}?放到冰箱?{1}?里了。",?elephant.Name,?refrigerator.Name));

????????????//第三步，關上冰箱門
????????????refrigerator.IsOpen?=?false;
????????????Console.WriteLine(string.Format("玉帝關上了?{0}?的冰箱門。",?refrigerator.Name));
????????}
????}

????class?Elephant
????{
????????public?string?Name?{?get;?set;?}
????????public?int?Weight{?get;?set;?}
????}

????class?Refrigerator
????{
????????public?string?Name?{?get;?set;?}
????????public?bool?IsOpen?{?get;?set;?}

????????private?object?m_Content;
????????public?object?Content
????????{
????????????get?{?return?this.m_Content;?}
????????????set
????????????{
????????????????if?(!this.IsOpen)
????????????????????throw?new?InvalidOperationException("冰箱門未打開，無法放進東西。");
????????????????if?(this.m_Content?!=?null)
????????????????????throw?new?InvalidOperationException("冰箱內有東西，無法放進新的東西。");

????????????????this.m_Content?=?value;
????????????}
????????}
????}

????class?Context
????{
????????public?Elephant?Elephant?{?get;?set;?}
????????public?Refrigerator?Refrigerator?{?get;?set;?}
????}
}

?

??????請大家先認真讀懂該代碼，該代碼不會有問題吧，如果有問題，那么還請你一定先讀懂該代碼再往下看。

??????后來，玉帝累了，他想啊，我堂堂玉帝，居然親自干這種沒含量的活，但是顧客是玉帝的玉帝，又不能不干。于是，玉帝找了兩個手下（把門大神、神象星宿）來幫他干活。

Code2
using?System;
using?System.Collections.Generic;

namespace?ConsoleApplication3
{
????class?Program
????{
????????static?void?Main(string[]?args)
????????{
????????????Emperor?emperor?=?new?Emperor();
????????????emperor.Init();

????????????while?(true)
????????????{
????????????????Console.WriteLine("首先給玉帝準備好大象和冰箱。");

????????????????Console.WriteLine("輸入大象的名字：");
????????????????string?elephantName?=?Console.ReadLine();
????????????????Console.WriteLine("輸入大象的體重：");
????????????????int?elephantWeight?=?int.Parse(Console.ReadLine());
????????????????Console.WriteLine("輸入冰箱的名字：");
????????????????string?refrigeratorName?=?Console.ReadLine();

????????????????Elephant?elephant?=?new?Elephant()
????????????????{
????????????????????Name?=?elephantName,
????????????????????Weight?=?elephantWeight
????????????????};
????????????????Refrigerator?refrigerator?=?new?Refrigerator()
????????????????{
????????????????????Name?=?refrigeratorName
????????????????};

????????????????Context?context?=?new?Context()
????????????????{
????????????????????Elephant?=?elephant,
????????????????????Refrigerator?=?refrigerator
????????????????};

????????????????emperor.ProcessRequest(context);

????????????????Console.WriteLine("是否要玉帝繼續把大象關進冰箱里？");
????????????????string?answer?=?Console.ReadLine();
????????????????if?(answer?==?"n")
????????????????????break;
????????????}
????????}
????}

????class?Emperor
????{
????????private?IList<IEmperorModule>?m_Modules;
????????public?Context?Context?{?get;?set;?}

????????public?void?Init()
????????{
????????????m_Modules?=?new?List<IEmperorModule>();
????????????m_Modules.Add(new?OpenCloseRefrigeratorDoorModule());
????????????m_Modules.Add(new?PutElephantToRefrigeratorModule());

????????????foreach?(IEmperorModule?module?in?this.m_Modules)
????????????{
????????????????module.Init(this);
????????????}
????????}

????????public?void?ProcessRequest(Context?context)
????????{
????????????this.Context?=?context;

????????????this.OnOpenRefrigeratorDoor();
????????????this.OnPutElephantToRefrigerator();
????????????this.OnCloseRefrigeratorDoor();
????????}

????????public?event?EventHandler?OpenRefrigeratorDoor;
????????public?event?EventHandler?PutElephantToRefrigerator;
????????public?event?EventHandler?CloseRefrigeratorDoor;

????????protected?virtual?void?OnOpenRefrigeratorDoor()
????????{
????????????EventHandler?handler?=?this.OpenRefrigeratorDoor;
????????????if?(handler?!=?null)
????????????{
????????????????handler(this,?EventArgs.Empty);
????????????}
????????}

????????protected?virtual?void?OnPutElephantToRefrigerator()
????????{
????????????EventHandler?handler?=?this.PutElephantToRefrigerator;
????????????if?(handler?!=?null)
????????????{
????????????????handler(this,?EventArgs.Empty);
????????????}
????????}

????????protected?virtual?void?OnCloseRefrigeratorDoor()
????????{
????????????EventHandler?handler?=?this.CloseRefrigeratorDoor;
????????????if?(handler?!=?null)
????????????{
????????????????handler(this,?EventArgs.Empty);
????????????}
????????}
????}

????class?Elephant
????{
????????public?string?Name?{?get;?set;?}
????????public?int?Weight{?get;?set;?}
????}

????class?Refrigerator
????{
????????public?string?Name?{?get;?set;?}
????????public?bool?IsOpen?{?get;?set;?}

????????private?object?m_Content;
????????public?object?Content
????????{
????????????get?{?return?this.m_Content;?}
????????????set
????????????{
????????????????if?(!this.IsOpen)
????????????????????throw?new?InvalidOperationException("冰箱門未打開，無法放進東西。");
????????????????if?(this.m_Content?!=?null)
????????????????????throw?new?InvalidOperationException("冰箱內有東西，無法放進新的東西。");

????????????????this.m_Content?=?value;
????????????}
????????}
????}

????class?Context
????{
????????public?Elephant?Elephant?{?get;?set;?}
????????public?Refrigerator?Refrigerator?{?get;?set;?}
????}

????interface?IEmperorModule
????{
????????void?Init(Emperor?emperor);
????}

????class?OpenCloseRefrigeratorDoorModule?:?IEmperorModule
????{
????????IEmperorModule?成員#region?IEmperorModule?成員
????????public?void?Init(Emperor?emperor)
????????{
????????????emperor.OpenRefrigeratorDoor?+=?new?EventHandler(this.OpenDoor);
????????????emperor.CloseRefrigeratorDoor?+=?new?EventHandler(this.CloseDoor);
????????}
????????#endregion

????????private?void?OpenDoor(object?sender,?EventArgs?e)
????????{
????????????Emperor?emperor?=?(Emperor)sender;
????????????Refrigerator?refrigerator?=?emperor.Context.Refrigerator;
????????????refrigerator.IsOpen?=?true;
????????????Console.WriteLine(string.Format("玉帝的把門大神打開了?{0}?的冰箱門。",?refrigerator.Name));
????????}

????????private?void?CloseDoor(object?sender,?EventArgs?e)
????????{
????????????Emperor?emperor?=?(Emperor)sender;
????????????Refrigerator?refrigerator?=?emperor.Context.Refrigerator;
????????????refrigerator.IsOpen?=?false;
????????????Console.WriteLine(string.Format("玉帝的把門大神關上了?{0}?的冰箱門。",?refrigerator.Name));
????????}
????}

????class?PutElephantToRefrigeratorModule?:?IEmperorModule
????{
????????IEmperorModule?成員#region?IEmperorModule?成員
????????public?void?Init(Emperor?emperor)
????????{
????????????emperor.PutElephantToRefrigerator?+=?new?EventHandler(this.PutElephantToRefrigerator);
????????}
????????#endregion

????????private?void?PutElephantToRefrigerator(object?sender,?EventArgs?e)
????????{
????????????Emperor?emperor?=?(Emperor)sender;
????????????Elephant?elephant?=?emperor.Context.Elephant;
????????????Refrigerator?refrigerator?=?emperor.Context.Refrigerator;
????????????refrigerator.Content?=?elephant;
????????????Console.WriteLine(string.Format("玉帝的神象星宿把大象?{0}?放到冰箱?{1}?里了。",?elephant.Name,?refrigerator.Name));
????????}
????}
}

?

??????觀測該代碼有哪些變化？玉帝增加了一個Init方法，該方法召集了那些干活的手下，并交待手下你們要干的事情（初始化）。所有手下都繼承自IEmperorModule接口，該接口有一個Init方法，以初始化該手下能干的活。玉帝的ProcessRequest方法不再親自干活了，而僅僅是在那邊喊，該開門了，該把大象放進去了，該關門了。

??????（來點題外話，上面代碼應用了模板方法模式，或者說是模板方法的變種。什么，不是，沒有抽象類，沒有抽象方法，沒有子類？請問，模板方法一定要有抽象類嗎？一定要有抽象方法嗎？一定要有子類嗎？我想，模板方法的精髓，在于它規定了特定的步驟算法，而這些步驟在必要的時候可以委托給其它方法實現。在傳統的模板方法中，是委托給子類實現，而在我們擁有委托的情況下，難道我們不能委托給其它類實現嗎？其實，我想，學習設計模式，不要拘泥于形式，而要掌握其精髓，并靈活運用。就Gof的23種設計模式來說，我覺得其精髓幾乎全部可由一句話概括。）

??????天有不測風云，人有旦夕禍福，某一天，這神象星宿病了，他趕不動超過1000斤的大象了，怎么辦？玉帝于是又召集了超級神象星宿，可但凡有點能耐的都有點脾氣，超級神象星宿表示，只有其它人趕不動的大象他才來趕。

Code3
using?System;
using?System.Collections.Generic;

namespace?ConsoleApplication3
{
????class?Program
????{
????????static?void?Main(string[]?args)
????????{
????????????Emperor?emperor?=?new?Emperor();
????????????emperor.Init();

????????????while?(true)
????????????{
????????????????Console.WriteLine("首先給玉帝準備好大象和冰箱。");

????????????????Console.WriteLine("輸入大象的名字：");
????????????????string?elephantName?=?Console.ReadLine();
????????????????Console.WriteLine("輸入大象的體重：");
????????????????int?elephantWeight?=?int.Parse(Console.ReadLine());
????????????????Console.WriteLine("輸入冰箱的名字：");
????????????????string?refrigeratorName?=?Console.ReadLine();

????????????????Elephant?elephant?=?new?Elephant()
????????????????{
????????????????????Name?=?elephantName,
????????????????????Weight?=?elephantWeight
????????????????};
????????????????Refrigerator?refrigerator?=?new?Refrigerator()
????????????????{
????????????????????Name?=?refrigeratorName
????????????????};

????????????????Context?context?=?new?Context()
????????????????{
????????????????????Elephant?=?elephant,
????????????????????Refrigerator?=?refrigerator
????????????????};

????????????????emperor.ProcessRequest(context);

????????????????Console.WriteLine("是否要玉帝繼續把大象關進冰箱里？");
????????????????string?answer?=?Console.ReadLine();
????????????????if?(answer?==?"n")
????????????????????break;
????????????}
????????}
????}

????class?Emperor
????{
????????private?IList<IEmperorModule>?m_Modules;
????????public?Context?Context?{?get;?set;?}

????????public?void?Init()
????????{
????????????m_Modules?=?new?List<IEmperorModule>();
????????????m_Modules.Add(new?OpenCloseRefrigeratorDoorModule());
????????????m_Modules.Add(new?PutElephantToRefrigeratorModule());
????????????m_Modules.Add(new?SuperPutElephantToRefrigeratorModule());

????????????foreach?(IEmperorModule?module?in?this.m_Modules)
????????????{
????????????????module.Init(this);
????????????}
????????}

????????public?void?ProcessRequest(Context?context)
????????{
????????????this.Context?=?context;

????????????this.OnOpenRefrigeratorDoor();
????????????this.OnPutElephantToRefrigerator();
????????????this.OnCloseRefrigeratorDoor();
????????}

????????public?event?EventHandler?OpenRefrigeratorDoor;
????????public?event?EventHandler?PutElephantToRefrigerator;
????????public?event?EventHandler?CloseRefrigeratorDoor;

????????protected?virtual?void?OnOpenRefrigeratorDoor()
????????{
????????????EventHandler?handler?=?this.OpenRefrigeratorDoor;
????????????if?(handler?!=?null)
????????????{
????????????????handler(this,?EventArgs.Empty);
????????????}
????????}

????????protected?virtual?void?OnPutElephantToRefrigerator()
????????{
????????????EventHandler?handler?=?this.PutElephantToRefrigerator;
????????????if?(handler?!=?null)
????????????{
????????????????handler(this,?EventArgs.Empty);
????????????}
????????}

????????protected?virtual?void?OnCloseRefrigeratorDoor()
????????{
????????????EventHandler?handler?=?this.CloseRefrigeratorDoor;
????????????if?(handler?!=?null)
????????????{
????????????????handler(this,?EventArgs.Empty);
????????????}
????????}
????}

????class?Elephant
????{
????????public?string?Name?{?get;?set;?}
????????public?int?Weight{?get;?set;?}
????}

????class?Refrigerator
????{
????????public?string?Name?{?get;?set;?}
????????public?bool?IsOpen?{?get;?set;?}

????????private?object?m_Content;
????????public?object?Content
????????{
????????????get?{?return?this.m_Content;?}
????????????set
????????????{
????????????????if?(!this.IsOpen)
????????????????????throw?new?InvalidOperationException("冰箱門未打開，無法放進東西。");
????????????????if?(this.m_Content?!=?null)
????????????????????throw?new?InvalidOperationException("冰箱內有東西，無法放進新的東西。");

????????????????this.m_Content?=?value;
????????????}
????????}
????}

????class?Context
????{
????????public?Elephant?Elephant?{?get;?set;?}
????????public?Refrigerator?Refrigerator?{?get;?set;?}

????????private?IDictionary<string,?object>?m_Items;
????????public?IDictionary<string,?object>?Items
????????{
????????????get
????????????{
????????????????if?(this.m_Items?==?null)
????????????????????this.m_Items?=?new?Dictionary<string,?object>();
????????????????return?this.m_Items;
????????????}
????????}
????}

????interface?IEmperorModule
????{
????????void?Init(Emperor?emperor);
????}

????class?OpenCloseRefrigeratorDoorModule?:?IEmperorModule
????{
????????IEmperorModule?成員#region?IEmperorModule?成員
????????public?void?Init(Emperor?emperor)
????????{
????????????emperor.OpenRefrigeratorDoor?+=?new?EventHandler(this.OpenDoor);
????????????emperor.CloseRefrigeratorDoor?+=?new?EventHandler(this.CloseDoor);
????????}
????????#endregion

????????private?void?OpenDoor(object?sender,?EventArgs?e)
????????{
????????????Emperor?emperor?=?(Emperor)sender;
????????????Refrigerator?refrigerator?=?emperor.Context.Refrigerator;
????????????refrigerator.IsOpen?=?true;
????????????Console.WriteLine(string.Format("玉帝的把門大神打開了?{0}?的冰箱門。",?refrigerator.Name));
????????}

????????private?void?CloseDoor(object?sender,?EventArgs?e)
????????{
????????????Emperor?emperor?=?(Emperor)sender;
????????????Refrigerator?refrigerator?=?emperor.Context.Refrigerator;
????????????refrigerator.IsOpen?=?false;
????????????Console.WriteLine(string.Format("玉帝的把門大神關上了?{0}?的冰箱門。",?refrigerator.Name));
????????}
????}

????class?PutElephantToRefrigeratorModule?:?IEmperorModule
????{
????????IEmperorModule?成員#region?IEmperorModule?成員
????????public?void?Init(Emperor?emperor)
????????{
????????????emperor.PutElephantToRefrigerator?+=?new?EventHandler(this.PutElephantToRefrigerator);
????????}
????????#endregion

????????private?void?PutElephantToRefrigerator(object?sender,?EventArgs?e)
????????{
????????????Emperor?emperor?=?(Emperor)sender;
????????????Elephant?elephant?=?emperor.Context.Elephant;
????????????Refrigerator?refrigerator?=?emperor.Context.Refrigerator;

????????????if?(elephant.Weight?>?1000)
????????????{
????????????????Console.WriteLine("這頭大象實在太重了，我神象星宿挪不動阿。");
????????????}
????????????else
????????????{
????????????????refrigerator.Content?=?elephant;
????????????????emperor.Context.Items["HasPutElephant"]?=?true;
????????????????Console.WriteLine(string.Format("玉帝的神象星宿把大象?{0}?放到冰箱?{1}?里了。",?elephant.Name,?refrigerator.Name));
????????????}
????????}
????}

????class?SuperPutElephantToRefrigeratorModule?:?IEmperorModule
????{
????????IEmperorModule?成員#region?IEmperorModule?成員
????????public?void?Init(Emperor?emperor)
????????{
????????????emperor.PutElephantToRefrigerator?+=?new?EventHandler(this.PutElephantToRefrigerator);
????????}
????????#endregion

????????private?void?PutElephantToRefrigerator(object?sender,?EventArgs?e)
????????{
????????????Emperor?emperor?=?(Emperor)sender;
????????????Elephant?elephant?=?emperor.Context.Elephant;
????????????Refrigerator?refrigerator?=?emperor.Context.Refrigerator;

????????????object?hasPutElephant;
????????????if?(emperor.Context.Items.TryGetValue("HasPutElephant",?out?hasPutElephant))
????????????{
????????????????if?(hasPutElephant?is?bool?&&?((bool)hasPutElephant)?==?true)
????????????????{
????????????????????Console.WriteLine("已經有人把大象放進冰箱了，我超級神象星宿就歇歇了。");
????????????????????return;
????????????????}
????????????}

????????????refrigerator.Content?=?elephant;
????????????emperor.Context.Items["HasPutElephant"]?=?true;
????????????Console.WriteLine(string.Format("玉帝的超級神象星宿把大象?{0}?放到冰箱?{1}?里了。",?elephant.Name,?refrigerator.Name));
????????}
????}
}

??????仔細琢磨該代碼，請問你發現了什么？如果你發現的是靈活的可擴展性和可配置性，以及各手下之間的交互，那么恭喜你，你悟性很高。如果你還發現了職責鏈模式，那么恭喜你，你悟性非常高。（該代碼中兩個神象星宿的交互完全可以通過在Context中增加一個bool值屬性來實現，之所有這里用Items字典，是為了演示如果你不具有修改Context的源代碼的時候，該如何處理。）

?????好了，Asp.net的設計思想講完了。什么，還沒開始？你沒發現我們的Program就是HttpRuntime、Emperor就是HttpApplication、Context就是HttpContext、IEmperorModule就是IHttpModule嗎？什么，沒發現？那么，讓我們來看看Asp.net的源代碼吧。（本想把整個方法的源代碼都貼上來，但是顯得過于冗長，因此刪掉非關鍵代碼，并以//……省略……代替。）

?

??????如此，你明白了嗎？

轉載于:https://www.cnblogs.com/aaa6818162/archive/2009/10/30/1592886.html

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