对于CS的分析你可以能会从页面开始，其实那并不是一个很好的方法，因为CS采用了MasterPage和内建的Theme与Skins，页面一层嵌套一层，如果你对CS页面执行机制不了解，或者你是初学者，这个时候可能就会碰壁，接着就放弃了对CS更深入的了解。我希望我的专题能从CS的运行过程开始一步一步地讲解，同时把ASP.NET的运行机理也表述出来，因此学习了解CS的过程就是对ASP.NET深入了解得过程。当然，我个人的开发经验与水平也是有限的，如果在专题中表述有问题，或者有疑问可以直接在文章的评论中直接指出，我将万分感谢你。
在分析CSHttpModule.cs的时候，你会看到这样两句代码：
CSEvents.UserKnown(csContext.User);
CSEvents.CSException(csException);
其实短短两行代码后面隐藏了Delegates与Events的大量运用，CS也通过这样的运用实现了一种模块化的处理机制，即CSModules。
打开CommunityServerWeb项目下的communityserver.config文件，这是CS的配置文件(与Web.config不同，communityserver.config主要配置的是CS内部的一些运行机制，而Web.config主要配置的是与Asp.net的交互)。找到文件中的这段：
<CSModules> <add name = "CSMembershipRulesModule" type = "CommunityServer.Components.CSMembershipRulesModule, CommunityServer.Components" /> <add name = "CSCatastrophicExceptionModule" type = "CommunityServer.Components.CSCatastrophicExceptionModule, CommunityServer.Components" /> <add name = "CSExceptionModule" type = "CommunityServer.Components.CSExceptionModule, CommunityServer.Components" /> <add name = "IrcCommands" type = "CommunityServer.Discussions.Components.IrcCommandsModule, CommunityServer.Discussions" /> <add name = "ForumCensorship" type = "CommunityServer.Discussions.Components.CensorshipModule, CommunityServer.Discussions" /> <add name = "ForumEmoticon" type = "CommunityServer.Discussions.Components.EmoticonModule, CommunityServer.Discussions" /> <add name = "ForumSourceCode" type = "CommunityServer.Discussions.Components.SourceCodeModule, CommunityServer.Discussions" /> <add name = "ForumHtmlScrubbing" type = "CommunityServer.Discussions.Components.HtmlScrubbingModule, CommunityServer.Discussions" /> <add name = "BBcodeToHtml" type = "CommunityServer.Discussions.Components.BBcodeToHtmlModule, CommunityServer.Discussions" /> <add name = "ForumPlainText" type = "CommunityServer.Discussions.Components.PlainTextModule, CommunityServer.Discussions" /> <add name = "WeblogCensorModule" type = "CommunityServer.Blogs.Components.CensorModule, CommunityServer.Blogs" /> <add name = "WeblogPostandArticleHtmlScrubbing" type = "CommunityServer.Blogs.Components.PostandArticleHtmlScrubbing, CommunityServer.Blogs" /> <add name = "WeblogFeedbackHtmlFormatting" type = "CommunityServer.Blogs.Components.FeedbackHtmlFormatting, CommunityServer.Blogs" /> <add name = "TrackbackModule" type = "CommunityServer.Blogs.Components.TrackbackModule, CommunityServer.Blogs" /> <add name = "XmlRpcPingModule" type = "CommunityServer.Blogs.Components.XmlRpcPingModule, CommunityServer.Blogs" /> <add name = "WeblogFormattingModule" type = "CommunityServer.Blogs.Components.WeblogFormattingModule, CommunityServer.Blogs" /> <add name = "PictureCensor" type = "CommunityServer.Galleries.Components.CensorPictureModule, CommunityServer.Galleries" /> <add name = "PictureHtmlScrubber" type = "CommunityServer.Galleries.Components.HtmlScrubberModule, CommunityServer.Galleries" /> <add name = "PictureComments" type = "CommunityServer.Galleries.Components.CommentModule, CommunityServer.Galleries" /> <!-- <add name = "MaxPictureSize" type = "CommunityServer.Galleries.Components.MaxPictureSizeModule, CommunityServer.Galleries" maxWidth="1024" maxHeight="768" quality="90" /> --> </CSModules>我们拿出其中的一个来分析运行过程，例：
<add name = "CSExceptionModule" type = "CommunityServer.Components.CSExceptionModule, CommunityServer.Components" />
这是CS中异常处理的模块，当发生异常的时候该模块将调用一个RedirectToMessage方法，提示一个友好的错误界面，告诉请求的用户有错误发生。那么CS系统是如何在发生错误的时候自动调用RedirectToMessage方法转向另外一个页面提示友好错误的呢？先打开CommunityServerComponents项目下Components文件夹中的CSApplication.cs
using System;using System.Collections;using System.ComponentModel;using System.Web.Caching;using System.Xml;using CommunityServer.Configuration; namespace CommunityServer.Components
{
#region Delegates
//Do we want one single delegate or a custom one for each type //public delegate void CSEventHandler(object sender, CSEventArgs e); public delegate void CSUserEventHandler(User user, CSEventArgs e); public delegate void CSPostEventHandler(Post post, CSEventArgs e); public delegate void CSSectionEventHandler(Section section, CSEventArgs e); public delegate void CSGroupEventHandler(Group group, CSEventArgs e); public delegate void CSExceptionHandler(CSException csEx, CSEventArgs e);
#endregion /// <summary> /// Summary description for CSApplication. /// </summary> public class CSApplication { #region private members private EventHandlerList Events = new EventHandlerList(); private static readonly object sync = new object(); private Hashtable modules = new Hashtable(); #endregion #region Event Keys (static) private static object EventAuthorizePost = new object(); private static object EventPrePostUpdate = new object(); private static object EventPreProcessPost = new object(); private static object EventPostPostUpdate = new object(); private static object EventRatePost = new object(); //private static object EventPreRenderPost = new object(); private static object EventPreUserUpdate = new object(); private static object EventPostUserUpdate = new object(); private static object EventUserRemove = new object(); private static object EventUserKnown = new object(); private static object EventUserValidated = new object(); private static object EventPreSectionUpdate = new object(); private static object EventPostSectionUpdate = new object(); private static object EventPreSectionGroupUpdate = new object(); private static object EventPostSectionGroupUpdate = new object(); private static object EventUnhandledException = new object(); #endregion #region cnstr private CSApplication() { } internal static CSApplication Instance() { const string key = "CSApplication"; CSApplication app = CSCache.Get(key) as CSApplication; if(app == null) { lock(sync) { app = CSCache.Get(key) as CSApplication; if(app == null) { CSConfiguration config = CSContext.Current.Config; XmlNode node = config.GetConfigSection("CommunityServer/CSModules"); app = new CSApplication(); if(node != null) { foreach(XmlNode n in node.ChildNodes) { if(n.NodeType != XmlNodeType.Comment) { switch(n.Name) { case "clear": app.modules.Clear(); break; case "remove": app.modules.Remove(n.Attributes["name"].Value); break; case "add": string name = n.Attributes["name"].Value; string itype = n.Attributes["type"].Value; Type type = Type.GetType(itype); if(type == null) throw new Exception(itype + " does not exist"); ICSModule mod = Activator.CreateInstance(type) as ICSModule; if(mod == null) throw new Exception(itype + " does not implement ICSModule or is not configured correctly"); mod.Init(app, n); app.modules.Add(name,mod); break; } } } } CacheDependency dep = new CacheDependency(null, new string[]{CSConfiguration.CacheKey}); CSCache.Max(key, app,dep); } } } return app; } #endregion #region Post Events #region Execute Events internal void ExecuteAuthorizePost() { ExecuteUserEvent(EventAuthorizePost,CSContext.Current.User); } internal void ExecutePrePostEvents(Post post, ObjectState state, ApplicationType appType) { ExecutePostEvent(EventPreProcessPost,post,state,appType); } internal void ExecutePrePostUpdateEvents(Post post, ObjectState state, ApplicationType appType) { ExecutePostEvent(EventPrePostUpdate,post,state,appType); } internal void ExecutePostPostUpdateEvents(Post post, ObjectState state, ApplicationType appType) { ExecutePostEvent(EventPostPostUpdate,post,state,appType); } internal void ExecuteRatePostEvents(Post post, ApplicationType appType) { ExecutePostEvent(EventRatePost,post,ObjectState.None,appType); } // internal void ExecutePrePostRender(Post post, ApplicationType appType)// {// ExecutePostEvent(EventPreRenderPost,post,ObjectState.None,appType);// } protected void ExecutePostEvent(object EventKey, Post post,ObjectState state, ApplicationType appType) { CSPostEventHandler handler = Events[EventKey] as CSPostEventHandler; if (handler != null) { handler(post, new CSEventArgs(state,appType)); } } #endregion #region Events /// <summary> /// Event raised before a user accesses a page which can be used to create content /// </summary> public event CSUserEventHandler AuthorizePost { add{Events.AddHandler(EventAuthorizePost, value);} remove{Events.RemoveHandler(EventAuthorizePost, value);} } /// <summary> /// Event raised before any post processing takes place /// </summary> public event CSPostEventHandler PreProcessPost { add{Events.AddHandler(EventPreProcessPost, value);} remove{Events.RemoveHandler(EventPreProcessPost, value);} } /// <summary> /// Fires after PreProcessPost but before the post change is commited to the datastore /// </summary> public event CSPostEventHandler PrePostUpdate { add{Events.AddHandler(EventPrePostUpdate, value);} remove{Events.RemoveHandler(EventPrePostUpdate, value);} } /// <summary> /// Fires after a post change is commited to the datastore /// </summary> public event CSPostEventHandler PostPostUpdate { add{Events.AddHandler(EventPostPostUpdate, value);} remove{Events.RemoveHandler(EventPostPostUpdate, value);} } /// <summary> /// Fires after a Post or Thread is rated /// </summary> public event CSPostEventHandler RatePost { add{Events.AddHandler(EventRatePost, value);} remove{Events.RemoveHandler(EventRatePost, value);} } // /// <summary>// /// Event raised before an individual post is rendered// /// </summary>// public event CSPostEventHandler PreRenderPost// {// add{Events.AddHandler(EventPreRenderPost, value);}// remove{Events.RemoveHandler(EventPreRenderPost, value);}// } #endregion #endregion #region User Events #region Execute Events internal void ExecuteUserValidated(User user) { ExecuteUserEvent(EventUserValidated,user); } internal void ExecuteUserKnown(User user) { ExecuteUserEvent(EventUserKnown,user); } internal void ExecutePreUserUpdate(User user, ObjectState state) { ExecuteUserEvent(EventPreUserUpdate,user,state,ApplicationType.Unknown); } internal void ExecutePostUserUpdate(User user, ObjectState state) { ExecuteUserEvent(EventPostUserUpdate,user,state,ApplicationType.Unknown); } internal void ExecuteUserRemove(User user) { ExecuteUserEvent(EventUserRemove,user,ObjectState.Delete,ApplicationType.Unknown); } protected void ExecuteUserEvent(object EventKey, User user) { ExecuteUserEvent(EventKey,user,ObjectState.None,ApplicationType.Unknown); } protected void ExecuteUserEvent(object EventKey, User user,ObjectState state, ApplicationType appType) { CSUserEventHandler handler = Events[EventKey] as CSUserEventHandler; if (handler != null) { handler(user, new CSEventArgs(state,appType)); } } #endregion #region Events /// <summary> /// Fires after a user's credentials have been validated. /// </summary> public event CSUserEventHandler UserValidated { add{Events.AddHandler(EventUserValidated, value);} remove{Events.RemoveHandler(EventUserValidated, value);} } /// <summary> /// Fires once the current user has been identified. This user may still be anonymous. /// </summary> public event CSUserEventHandler UserKnown { add{Events.AddHandler(EventUserKnown, value);} remove{Events.RemoveHandler(EventUserKnown, value);} } /// <summary> /// Fires before a User is saved/updated to the datastore /// </summary> public event CSUserEventHandler PreUserUpdate { add{Events.AddHandler(EventPreUserUpdate, value);} remove{Events.RemoveHandler(EventPreUserUpdate, value);} } /// <summary> /// Fires after a User is saved/updated to the datastore /// </summary> public event CSUserEventHandler PostUserUpdate { add{Events.AddHandler(EventPostUserUpdate, value);} remove{Events.RemoveHandler(EventPostUserUpdate, value);} } /// <summary> /// Fires before a User is removed from the datastore. /// </summary> public event CSUserEventHandler UserRemove { add{Events.AddHandler(EventUserRemove, value);} remove{Events.RemoveHandler(EventUserRemove, value);} } #endregion #endregion #region Section Events internal void ExecutePreSectionUpdate(Section section, ObjectState state, ApplicationType appType) { CSSectionEventHandler handler = Events[EventPreSectionUpdate] as CSSectionEventHandler; if (handler != null) { handler(section, new CSEventArgs(state,appType)); } } internal void ExecutePostSectionUpdate(Section section, ObjectState state, ApplicationType appType) { CSSectionEventHandler handler = Events[EventPostSectionUpdate] as CSSectionEventHandler; if (handler != null) { handler(section, new CSEventArgs(state,appType)); } } /// <summary> /// Event raised before a section change is committed to the datastore (create/update) /// </summary> public event CSSectionEventHandler PreSectionUpdate { add{Events.AddHandler(EventPreSectionUpdate, value);} remove{Events.RemoveHandler(EventPreSectionUpdate, value);} } /// <summary> /// Event raised after a section chage is committed to the data store /// </summary> public event CSSectionEventHandler PostSectionUpdate { add{Events.AddHandler(EventPostSectionUpdate, value);} remove{Events.RemoveHandler(EventPostSectionUpdate, value);} } #endregion #region Group Events internal void ExecutePreSectionGroupUpdate(Group group, ObjectState state, ApplicationType appType) { CSGroupEventHandler handler = Events[EventPreSectionGroupUpdate] as CSGroupEventHandler; if (handler != null) { handler(group, new CSEventArgs(state,appType)); } } internal void ExecutePostSectionGroupUpdate(Group group, ObjectState state, ApplicationType appType) { CSGroupEventHandler handler = Events[EventPostSectionGroupUpdate] as CSGroupEventHandler; if (handler != null) { handler(group, new CSEventArgs(state,appType)); } } /// <summary> /// Event raised before a group chage is committed to the datastore (create/update) /// </summary> public event CSGroupEventHandler PreSectionGroupUpdate { add{Events.AddHandler(EventPreSectionGroupUpdate, value);} remove{Events.RemoveHandler(EventPreSectionGroupUpdate, value);} } /// <summary> /// Event raised after a group chage is committed to the data store /// </summary> public event CSGroupEventHandler PostSectionGroupUpdate { add{Events.AddHandler(EventPostSectionGroupUpdate, value);} remove{Events.RemoveHandler(EventPostSectionGroupUpdate, value);} } #endregion #region Exceptions /// <summary> /// Event raised before a group chage is committed to the datastore (create/update) /// </summary> public event CSExceptionHandler CSException { add{Events.AddHandler(EventUnhandledException, value);} remove{Events.RemoveHandler(EventUnhandledException, value);} } internal void ExecuteCSExcetion(CSException csEx) { CSExceptionHandler handler = Events[EventUnhandledException] as CSExceptionHandler; if (handler != null) { handler(csEx,new CSEventArgs()); } } #endregion }
}文件太长，我们抓出关键的部分来分析：
public delegate void CSExceptionHandler(CSException csEx, CSEventArgs e);这里先申明一个委托，相当于一个函数指针。在通俗一点理解它就是一个跑腿的，专管传递对象与对象间的调用信息。
接下来：
internal static CSApplication Instance() { const string key = "CSApplication"; CSApplication app = CSCache.Get(key) as CSApplication; if(app == null) { lock(sync) { app = CSCache.Get(key) as CSApplication; if(app == null) { CSConfiguration config = CSContext.Current.Config; XmlNode node = config.GetConfigSection("CommunityServer/CSModules"); app = new CSApplication(); if(node != null) { foreach(XmlNode n in node.ChildNodes) { if(n.NodeType != XmlNodeType.Comment) { switch(n.Name) { case "clear": app.modules.Clear(); break; case "remove": app.modules.Remove(n.Attributes["name"].Value); break; case "add": string name = n.Attributes["name"].Value; string itype = n.Attributes["type"].Value; Type type = Type.GetType(itype); if(type == null) throw new Exception(itype + " does not exist"); ICSModule mod = Activator.CreateInstance(type) as ICSModule; if(mod == null) throw new Exception(itype + " does not implement ICSModule or is not configured correctly"); mod.Init(app, n); app.modules.Add(name,mod); break; } } } } CacheDependency dep = new CacheDependency(null, new string[]{CSConfiguration.CacheKey}); CSCache.Max(key, app,dep); } } } return app; }这段很重要，通过读取communityserver.config文件的<CSModules>，初始化每个CSModule，注意，初始化后并且调用了这些CSModule中的Init方法。具体看看这些Module中的Init都做了什么，打开CommunityServerComponents项目下的Components文件夹中的CSExceptionModule.cs：
using System;using System.Web; namespace CommunityServer.Components{ /// <summary> /// Summary description for CSExceptionModule. /// </summary> public class CSExceptionModule : ICSModule { public CSExceptionModule() { // // TODO: Add constructor logic here // } #region ICSModule Members public void Init(CSApplication csa, System.Xml.XmlNode node) { csa.CSException +=new CSExceptionHandler(csa_CSException); } #endregion private void csa_CSException(CSException csEx, CSEventArgs e) { CSContext csContext = CSContext.Current; if (csEx.ExceptionType != CSExceptionType.UnknownError && csContext.IsWebRequest) { RedirectToMessage(csContext.Context, csEx); } } private static void RedirectToMessage (HttpContext context, CSException exception) { if ((exception.InnerException != null) && ( exception.InnerException is CSException)) { CSException inner = (CSException) exception.InnerException; } context.Response.Redirect(Globals.GetSiteUrls().Message( exception.ExceptionType ), true); } }}哈哈，原来在Init方法里把一个CSExceptionHandler委托添加到CSException事件上，这个委托指向csa_CSException方法，还是通俗点说：如果CSException这个事件发生了，CSExceptionHandler这个跑腿的委托就会马上告诉csa_CSException方法要他执行，如果事件没有被激发就什么也不做。
名词: event 关键字使您得以指定当代码中的某些“事件”发生时调用的委托。此委托可以有一个或多个关联的方法，当代码指示该事件已发生时将调用关联的方法。
那么这个CSException又是怎么回事？在哪里定义的？我们回到CSApplication.cs文件中，看样几行：
public event CSExceptionHandler CSException { add{Events.AddHandler(EventUnhandledException, value);} remove{Events.RemoveHandler(EventUnhandledException, value);} }这里定义了一个CSException事件，而事件发生的时候只能用CSExceptionHandler这个委托来做跑腿的。其实CS中是把委托都存放在了一个EventHandlerList中，因此此处你可以看到add与remove,
这是访问器的声明，用于添加或移除客户代码中的事件处理程序，这样做的好处是公开大量的事件但不为每个事件分配字段，而是使用EventHandlerList存储这些事件实例。为了理解事件的调用执行过程，我们还必须看几个文件：CSEvents.cs、CSEventArgs.cs：CSEventArgs.cs存储事件的数据，这个很好理解，它继承自EventArgs。当事件发生时CSEventArgs用来传递事件的信息，这里传递两个值：ObjectState与ApplicationType(可以在Enumerations文件夹下找到这两个枚举的内容)
CSEvents.cs这是对事件调用的一个包装器，看异常处理的包装：
public static void CSException(CSException csEx) { CSApplication.Instance().ExecuteCSExcetion(csEx); }这里先调用CSApplication.Instance()方法，实例化一个CSApplication对象，如果你是第一次调用Instance()方法，就实例化所有在<CSModules>中配置的类，并且调用他们的Init方法(在CSModules中配置的这些类，都实现了ICSModule接口，而这个接口要求继承他的类都具备Init方法)，执行Init方法的目的就是把委托添加到事件上，使委托指向的方法可以在事件触发的时候被调用。实例化后再调用ExecuteCSExcetion方法并且传递CSException的实例，ExecuteCSExcetion方法如下：
internal void ExecuteCSExcetion(CSException csEx) { CSExceptionHandler handler = Events[EventUnhandledException] as CSExceptionHandler; if (handler != null) { handler(csEx,new CSEventArgs()); } }先通过对EventHandlerList索引访问，即Events[EventUnhandledException]，从列表中找到这个CSExceptionHandler事件，如果不为null就执行它。EventUnhandledException又是什么，其实这只是一个Key，用来标示存储的事件。
有必要总结一下，不然你会被这种调用来调用去的关系搞得一头雾水，
以异常处理为例：
1：在错误发生后，调用Application_OnError方法；
2：在方法的最后调用CSEvents.CSException(csException)；
3：进入CSEvents包装器，调用CSApplication.Instance().ExecuteCSExcetion(csEx);
4：执行CSApplication.Instance()方法，如果是第一次执行就根据communityserver.config文件中的配置，把所有的CSModules实例化，并且调用ICSModule接口类中的Init方法，然后缓存这些实例化的类(如果是第二次访问就从缓存中读取)。
5：在实现ICSModule接口的类中，如CSExceptionModule.cs，Init方法是给事件添加委托的过程，这个过程中实现了委托指向的一个或者多个方法与事件进行关联，异常处理的方法csa_CSException(CSException csEx, CSEventArgs e)就是在这里被关联到异常事件上的。
6:经过上面几步后，CS系统接着调用ExecuteCSExcetion方法，在ExecuteCSExcetion方触发了CSException事件
7：CSException事件被触发后，就执行事件中委托所指向的函数，这里是CSExceptionModule.cs文件中的private void csa_CSException(CSException csEx, CSEventArgs e)。
CS如此大量的使用Delegates与Events带来了什么，也许你会认为它这样是把问题复杂化，而且觉得这非常没有必要，完全可以在异常处理的最后调用处理方法即可，何必通过事件来回周转！最后说明一下这样做的重要性：
1：通过事件使调用方法者与方法本身隔离，如在CSHttpModule.cs文件中的Application_OnError方法触发CSEvents.CSException事件，而事件要做些什么处理，需要调用什么方法Application_OnError根本不知道。如果你要改变CSEvents.CSException事件处理方法的结构，甚至十处理方法的名称，Application_OnError也不需要改动，因为他根本不关心具体的实现，它的任务只是触发这个事件。
2：如果你想一个方法调用多个方法，普通的做法就是在方法中一次调用或者在方法中嵌套调用。这样做并不是一个好的设计模式，而事件可以通过委托调用多个委托指向的方法(在异常处理中只指向了一个方法，当然你可以指向任意N个方法)，而这种调用也是相互隔离的，被调用的方法并不致到谁调用它，而调用者也不关心它调用谁。
3：模块化，你的代码直接没有非常的多紧密联系，而是通过事件来通知处理方法，在CS中又加入了xml的配置文件，使得这样的模块化更突出，你甚至可以把处理异常的类单独编译在一个dll中。
好处还有很多…
在CS中，对Post内容的不良信息过滤也是通过这样的机制完成的，运行的过程基本一致，只是调用不同的事件处理方法，你可以自己分析。