自从有了html与http，就有了浏览器与Web服务器，并有了Web应用，最初的交互模式是这样的：
该模式很好地运行了很多年。然而，随着计算机应用的发展，人们越来越不满足于只有静态内容的页面，而由某种机制动态产生html等代码的需求越来越迫切，于是，很多技术就应运而生，ASP.NET就是这样一种技术。从本质上讲，ASP.NET就是一种服务器端动态产生html、css、javascript等浏览器认识的代码的技术。ASP.NET的交互模式如下：
由该图可知，ASP.NET必须解决两大问题，一是如何与Web服务器（一般就是指IIS）进行交互，二是如何根据不同请求产生不同的html等代码。
***个问题，根据IIS版本（5.*，6.0，7.0）的不同，ASP.NET具有不同的进程模式与不同的交互模式，该问题不是本篇要讲述的。一般来说，大家不必关心该问题，而且要了解该问题，又必须清楚IIS各个版本的模型，而各个版本又各有各的不同，因此，我基本不准备讲述这个问题，大家有兴趣的话，可以自行搜索相关资料。
我们来讨论第二个问题，这里首先要说明的是，因为IIS7.0进程模式的变化比较大，我也没去了解IIS7.0的模型，因此，以下讲述及以后讲述将只针对IIS5.*与IIS6.0。我们有理由认为，针对IIS5.*与IIS6.0的讲述一般同样适用于IIS7.0。
先且按下该问题不表，我们来看一段请求玉帝把大象放到冰箱里的代码（为什么不是上帝？因为我中华不归上帝管），请大家先跟着我的思路来，别急，别急。
using System;
namespace ConsoleApplication3
11_Open_Text').style.display='none'; document.getElementById('Codehighlighter1_45_2811_Closed_Image').style.display='inline'; document.getElementById('Codehighlighter1_45_2811_Closed_Text').style.display='inline';" src="/files/uploadimg/20090423/1047402.gif" align=top>{
class Program
{
static void Main(string[] args)
{
Emperor emperor = new Emperor();
while (true)
{
Console.WriteLine("首先给玉帝准备好大象和冰箱。");
Console.WriteLine("输入大象的名字：");
string elephantName = Console.ReadLine();
Console.WriteLine("输入大象的体重：");
int elephantWeight = int.Parse(Console.ReadLine());
Console.WriteLine("输入冰箱的名字：");
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("是否要玉帝继续把大象关进冰箱里？");
string answer = Console.ReadLine();
if (answer == "n")
break;
}
}
}
class Emperor
{
public void ProcessRequest(Context context)
{
Elephant elephant = context.Elephant;
Refrigerator refrigerator = context.Refrigerator;
//***步，打开冰箱门
refrigerator.IsOpen = true;
Console.WriteLine(string.Format("玉帝打开了 {0} 的冰箱门。", refrigerator.Name));
//第二步，把大象放进去
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，关上冰箱门
refrigerator.IsOpen = false;
Console.WriteLine(string.Format("玉帝关上了 {0} 的冰箱门。", 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("冰箱门未打开，无法放进东西。");
if (this.m_Content != null)
throw new InvalidOperationException("冰箱内有东西，无法放进新的东西。");
this.m_Content = value;
}
}
}
class Context
{
public Elephant Elephant { get; set; }
public Refrigerator Refrigerator { get; set; }
}
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请大家先认真读懂该代码，该代码不会有问题吧，如果有问题，那么还请你一定先读懂该代码再往下看。
后来，玉帝累了，他想啊，我堂堂玉帝，居然亲自干这种没含量的活，但是顾客是玉帝的玉帝，又不能不干。于是，玉帝找了两个手下（把门大神、神象星宿）来帮他干活。
_Text_112146').style.display='none'; document.getElementById('Code_Open_Image_112146').style.display='inline'; document.getElementById('Code_Open_Text_112146').style.display='inline';" height=16 src="/files/uploadimg/20090423/1047403.gif" width=11 align=top>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("首先给玉帝准备好大象和冰箱。");
Console.WriteLine("输入大象的名字：");
string elephantName = Console.ReadLine();
Console.WriteLine("输入大象的体重：");
int elephantWeight = int.Parse(Console.ReadLine());
Console.WriteLine("输入冰箱的名字：");
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("是否要玉帝继续把大象关进冰箱里？");
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("冰箱门未打开，无法放进东西。");
if (this.m_Content != null)
throw new InvalidOperationException("冰箱内有东西，无法放进新的东西。");
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 成员#region IEmperorModule 成员
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("玉帝的把门大神打开了 {0} 的冰箱门。", 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("玉帝的把门大神关上了 {0} 的冰箱门。", refrigerator.Name));
}
}
class PutElephantToRefrigeratorModule : IEmperorModule
{
IEmperorModule 成员#region IEmperorModule 成员
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));
}
}
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观测该代码有哪些变化？玉帝增加了一个Init方法，该方法召集了那些干活的手下，并交待手下你们要干的事情（初始化）。所有手下都继承自IEmperorModule接口，该接口有一个Init方法，以初始化该手下能干的活。玉帝的ProcessRequest方法不再亲自干活了，而仅仅是在那边喊，该开门了，该把大象放进去了，该关门了。
来点题外话，上面代码应用了模板方法模式，或者说是模板方法的变种。什么，不是，没有抽象类，没有抽象方法，没有子类？请问，模板方法一定要有抽象类吗？一定要有抽象方法吗？一定要有子类吗？我想，模板方法的精髓，在于它规定了特定的步骤算法，而这些步骤在必要的时候可以委托给其它方法实现。在传统的模板方法中，是委托给子类实现，而在我们拥有委托的情况下，难道我们不能委托给其它类实现吗？其实，我想，学习设计模式，不要拘泥于形式，而要掌握其精髓，并灵活运用。就Gof的23种设计模式来说，我觉得其精髓几乎全部可由一句话概括。）
天有不测风云，人有旦夕祸福，某一天，这神象星宿病了，他赶不动超过1000斤的大象了，怎么办？玉帝于是又召集了超级神象星宿，可但凡有点能耐的都有点脾气，超级神象星宿表示，只有其它人赶不动的大象他才来赶。
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("首先给玉帝准备好大象和冰箱。");
Console.WriteLine("输入大象的名字：");
string elephantName = Console.ReadLine();
Console.WriteLine("输入大象的体重：");
int elephantWeight = int.Parse(Console.ReadLine());
Console.WriteLine("输入冰箱的名字：");
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("是否要玉帝继续把大象关进冰箱里？");
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
Id('Codehighlighter1_3485_3771_Closed_Text').style.display='none'; document.getElementById('Codehighlighter1_3485_3771_Open_Image').style.display='inline'; document.getElementById('Codehighlighter1_3485_3771_Open_Text').style.display='inline';" src="/files/uploadimg/20090423/1047407.gif" align=top> {
if (!this.IsOpen)
throw new InvalidOperationException("冰箱门未打开，无法放进东西。");
if (this.m_Content != null)
throw new InvalidOperationException("冰箱内有东西，无法放进新的东西。");
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
none; BORDER-LEFT: #808080 1px solid; BORDER-BOTTOM: #808080 1px solid; BACKGROUND-COLOR: #ffffff">{
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 成员#region IEmperorModule 成员
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("玉帝的把门大神打开了 {0} 的冰箱门。", 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("玉帝的把门大神关上了 {0} 的冰箱门。", refrigerator.Name));
}
}
class PutElephantToRefrigeratorModule : IEmperorModule
{
IEmperorModule 成员#region IEmperorModule 成员
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("这头大象实在太重了，我神象星宿挪不动阿。");
}
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 成员#region IEmperorModule 成员
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("已经有人把大象放进冰箱了，我超级神象星宿就歇歇了。");
return;
}
}
refrigerator.Content = elephant;
emperor.Context.Items["HasPutElephant"] = true;
Console.WriteLine(string.Format("玉帝的超级神象星宿把大象 {0} 放到冰箱 {1} 里了。", elephant.Name, refrigerator.Name));
}
}
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仔细琢磨该代码，请问你发现了什么？如果你发现的是灵活的可扩展性和可配置性，以及各手下之间的交互，那么恭喜你，你悟性很高。如果你还发现了职责链模式，那么恭喜你，你悟性非常高。（该代码中两个神象星宿的交互完全可以通过在Context中增加一个bool值属性来实现，之所有这里用Items字典，是为了演示如果你不具有修改Context的源代码的时候，该如何处理。）
好了，ASP.NET的设计思想讲完了。什么，还没开始？你没发现我们的Program就是HttpRuntime、Emperor就是HttpApplication、Context就是HttpContext、IEmperorModule就是IHttpModule吗？什么，没发现？那么，让我们来看看ASP.NET的源代码吧。（本想把整个方法的源代码都贴上来，但是显得过于冗长，因此删掉非关键代码，并以//……省略……代替。）
如此，你明白了吗？
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