浅谈ASP.NET的Postback
摘要：说道ASP.NET的Postback，就得说Web Page的生命周期，但是Web Page的生命周期却不是三言两语就能够说得清楚的，所以在这里单纯站的编程的角度，撇开Web Page 的生命周期浅谈Postback。
[1] 浅谈ASP.NET的Postback[2] 浅谈ASP.NET的Postback
说道ASP.NET的Postback，就得说Web Page的生命周期，但是Web Page的生命周期却不是三言两语就能够说得清楚的，所以在这里单纯站的编程的角度，撇开Web Page 的生命周期浅谈Postback。
我们知道，无论是ASP.NET1.x,2.0，甚至是以后的版本，ASP.NET最终Render到Client端通过浏览器浏览的都是一样：一个单纯的HTML。Client通过Submit Form的方式将填入Form的数据提交给Server进行处理。我们现在来看看ASP.NET整个Postback程序处理的过程。
首先我们通过一个Sample来看ASP.NET如何处理一个通过Click一个Button引起的Postback。下面是Web Page的HTML：
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" 
%>
DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head runat="server"> <title>Test Pagetitle>head><body> <form id="form1" runat="server"> <div> <asp:Label runat="server" ID="LabelMessage" ForeColor="red">asp:Label> div> <div> <asp:Button runat="server" ID="Button1" Text="Button1" OnClick="Button1_Click" OnCommand="Button_Command" CommandArgument="Button1" />
<asp:Button runat="server" ID="Button2" Text="Button2" OnClick="Button2_Click" OnCommand="Button_Command" CommandArgument="Button2" UseSubmitBehavior="false" />
<asp:Button runat="server" ID="Button3" Text="Button3" OnClick="Button3_Click" OnCommand="Button_Command" CommandArgument="Button3" UseSubmitBehavior="false" />
div> form>body>html>很简单，定义了3个Button，分别注册了他们的两个Event：Click和Command。3个Button的Command Event Hander是一样的：Button_Command，通过指定的CommandArgument来让Event Handler判断到底是哪个Button触发了Command Event。
下面是Code Behind：
using System;using System.Data;using System.Configuration;using System.Web;using System.Web.Security;using System.Web.UI;using System.Web.UI.WebControls;using System.Web.UI.WebControls.WebParts;using System.Web.UI.HtmlControls;public partial class _Default : System.Web.UI.Page{ 
protected void Page_Load(object sender, EventArgs e)
{
} protected void Button1_Click(object sender, EventArgs e) { string message = string.Format("The {0} event of {1} is fired", "Click", "Button1"); this.LabelMessage.Text = message; } protected void Button2_Click(object sender, EventArgs e) { string message = string.Format("The {0} event of {1} is fired", "Click", "Button2"); this.LabelMessage.Text = message; } protected void Button3_Click(object sender, EventArgs e) { string message = string.Format("The {0} event of {1} is fired", "Click", "Button3"); this.LabelMessage.Text = message; } protected void Button_Command(object sender, CommandEventArgs e) { string message = string.Format("The {0} event of {1} is fired", "Command", e.CommandArgument);
this.LabelMessage.Text += "; " + message; }
}我们来运行这个Page，并Click某个按钮（比如Button2）：
我们通过最上方的Message可以看出，Button2的Click Event和Command先后触发。
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