【Step by Step】编写代码验证一个ASP.NET应用程序和页面的生命周期

时间：2011-06-14 来源：李志鹏

我们知道ASP.NET Page的生命周期实际上是ASP.NET Application的生命周期的一部分。这个周期经历了HTTP Module => HTTP Handler => ASP.NET Page => Http Module这样一个过程。如果我们能更好地掌握这样一个过程，那么对单个ASP.NET Page的生命周期也能更好地了解：

下面介绍如何编写一个简单的ASP.NET 页面和一个简单的HttpModule，对MSDN里提到的ASP.NET的生命周期进行验证

1. 首先使用Visual Studio 2010建立一个空的ASP.NET网站（ASP.NET 4.0）

2. 添加一个Default.aspx，添加三个ASP.NET控件，分别为TextBox，Button和Validator：

<form id="form1" runat="server">
<div>
        
<asp:TextBox ID="txtName" runat="server"></asp:TextBox>
<asp:Button ID="btnSubmit" runat="server" Text="OK" onclick="btnSubmit_Click" />
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ErrorMessage="Please input your name!" ControlToValidate="txtName" ForeColor="#FF3300">
</asp:RequiredFieldValidator>
        
</div>
</form>

3. 添加一个ASP.NEt的App_code文件夹，新建一个类，内容为：

    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Web;
    
    public class TestClass : IHttpModule
    {
        HttpApplication httpApp;
        public static List<string> EventList = new List<string>();
    
        public TestClass()
        {
        }
    
        public void Dispose()
        { }
    
        public void Init(HttpApplication context)
        {
            this.httpApp = context;
            //EventList.Clear();
            EventList.Add("Initiated");
            context.BeginRequest += new EventHandler(context_BeginRequest);
            context.AuthenticateRequest += new EventHandler(context_AuthenticateRequest);
            context.AuthorizeRequest += new EventHandler(context_AuthorizeRequest);
            context.ResolveRequestCache += new EventHandler(context_ResolveRequestCache);
            context.AcquireRequestState += new EventHandler(context_AcquireRequestState);
            context.PreRequestHandlerExecute += new EventHandler(context_PreRequestHandlerExecute);
            context.PostReleaseRequestState += new EventHandler(context_PostReleaseRequestState);
            context.ReleaseRequestState += new EventHandler(context_ReleaseRequestState);
            context.UpdateRequestCache += new EventHandler(context_UpdateRequestCache);
            context.EndRequest += new EventHandler(context_EndRequest);
        }
    
        private void context_EndRequest(object sender, EventArgs e)
        {
            EventList.Add("HTTP Modules: End Request <hr>");
            foreach (string str in EventList)
            {
                httpApp.Response.Write(str + "<br>");
            }
    
            EventList.Clear();
        }
    
        void context_UpdateRequestCache(object sender, EventArgs e)
        {
            EventList.Add("HTTP Modules: Update Request Cache");
        }
    
        void context_ReleaseRequestState(object sender, EventArgs e)
        {
            EventList.Add("HTTP Modules: Release Request State");
        }
    
        void context_PostReleaseRequestState(object sender, EventArgs e)
        {
            EventList.Add("HTTP Modules: Post Release Request State");
        }
    
        void context_PreRequestHandlerExecute(object sender, EventArgs e)
        {
            EventList.Add("HTTP Modules: Pre Request Handler Execution");
        }
    
        void context_AcquireRequestState(object sender, EventArgs e)
        {
            EventList.Add("HTTP Modules: Acquire Request State");
        }
    
        void context_ResolveRequestCache(object sender, EventArgs e)
        {
            EventList.Add("HTTP Modules: Resolve Request");
        }
    
        void  context_AuthorizeRequest(object sender, EventArgs e)
        {
            EventList.Add("HTTP Modules: Authorize Request");
        }
    
        void  context_AuthenticateRequest(object sender, EventArgs e)
        {
            EventList.Add("HTTP Modules: AuthenticateRequest");
        }
    
        void context_BeginRequest(object sender, EventArgs e)
        {
            EventList.Add("HTTP Modules: Begin Request");
        }
    }

4. 修改刚才的Default.aspx的后台cs代码：

    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Web;
    using System.Web.UI;
    using System.Web.UI.WebControls;
    
    public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Init()
        {
            TestClass.EventList.Add("ASP.NET Page: Page_Init");
        }
    
        protected void Page_Load(object sender, EventArgs e)
        {
            TestClass.EventList.Add("ASP.NET Page: Page_Load");
        }
    
        public override void Validate()
        {
            TestClass.EventList.Add("ASP.NET Page: Validated");
            base.Validate();
        }
    
    
        protected void btnSubmit_Click(object sender, EventArgs e)
        {
            TestClass.EventList.Add("ASP.NET Page: Event");
        }
    
        protected override void Render(HtmlTextWriter writer)
        {
            TestClass.EventList.Add("ASP.NET Page: Render");   
            base.Render(writer);
        }
    
        protected void Page_Unload(object sender, EventArgs e)
        {
            TestClass.EventList.Add("ASP.NET Page: Unload");
        }
    
    }

5. 修改web.config内容如下：

    <configuration>
        <system.web>
            <compilation debug="true" targetFramework="4.0"/>
        </system.web>
        <system.web>
        <httpModules>
          <add name="TestClass" type="TestClass"/>
        </httpModules>
        </system.web>
    </configuration>

6. Ctrl+F5执行，在浏览器里可以看到：

7. 在文本框内输入内容，可得：

结论：1. Module只初始化了一次，当页面postback的时候，module不会再初始化。

　　2. Validate和Event事件在页面第一次初始化的时候不会触发，但是由于页面本身存在validate控件和事件按钮，所以这两个事件在第二次会被触发。

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本文参考了codeproject.com的如下一篇文章http://www.codeproject.com/KB/aspnet/ASPDOTNETPageLifecycle.aspx