您的位置：首页 > 编程语言 > ASP

浅谈ASP.NET的Postback 实例代码第1/2页

2009-08-07 00:00 621 查看

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 Page</title> 
</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。
这篇Blog的主旨就是从方法调用的角度讲述整个程序运行的过程：从HTML 被Render到Client端，到用户Click某个按钮，输入被Postback到Server端，并触发两个Event，执行Event Handler打印出相关的Message。
首先我们来看看ASP.NET设计的Page Render到Client端的HTML是什么样子：

<!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> 
<title> 
Test Page 
</title> 
</head> 
<body> 
<form name="form1" method="post" action="Default.aspx" id="form1"> 
<div> 
<input type="hidden" name="__EVENTTARGET" id="__EVENTTARGET" value="" /> 
<input type="hidden" name="__EVENTARGUMENT" id="__EVENTARGUMENT" value="" /> 
<input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="/wEPDwUKMTA0NDQ2OTE5OWRk281L4eAk7iZT10hzg+BeOyoUWBQ=" /> 
</div> 
<script type="text/javascript"> 
<!-- 
var theForm = document.forms['form1']; 
if (!theForm) { 
theForm = document.form1; 
} 
function __doPostBack(eventTarget, eventArgument) { 
if (!theForm.onsubmit || (theForm.onsubmit() != false)) { 
theForm.__EVENTTARGET.value = eventTarget; 
theForm.__EVENTARGUMENT.value = eventArgument; 
theForm.submit(); 
} 
} 
// --> 
</script> 
<div> 
<span id="LabelMessage" style="color:Red;"></span> 
</div> 
<div> 
<input type="submit" name="Button1" value="Button1" id="Button1" /> 
<input type="button" name="Button2" value="Button2" onclick="javascript:__doPostBack('Button2','')" id="Button2" /> 
<input type="button" name="Button3" value="Button3" onclick="javascript:__doPostBack('Button3','')" id="Button3" /> 
</div> 
</form> 
</body> 
</html>

内容来自用户分享和网络整理，不保证内容的准确性，如有侵权内容，可联系管理员处理

标签：

相关文章推荐

新的分享

章节导航