作为ASP.NET 2.0 的新特性，ICallbackEventHandler给我们完整的AJAX体验，而且实现/控制更加简单；但事实上ICallbackEventHandler并不是一个完整的AJAX实现，否则也不会有Atlas的开发~
目前来看，ICallbackEventHandler是一种轻量级的类AJAX实现，优点是不用周折于客户端创建XMLHttpRequest对象时的兼容性问题，而把重点放在局部HttpRequest的处理上；缺点（至少目前是）是向服务端提交数据不太方便，不能是Post方式，只能是一个字符串~
下面是随意写的一个hello word,
Page
<%@ 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>Hello ICallBackHandler</title></head><body> <form id="form1" runat="server"> <div> <br /> <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox> <asp:Button ID="Button1" runat="server" Text="Button" /><br /> <br /> <br /> <br /> <div style="color:Red" id="ddd"></div> </div> </form></body></html>
Code-behind
using System;using System.Data;using System.Configuration;using System.Collections;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,ICallbackEventHandler{
private const string CALLBACK_PARAM = "callbackTest"; protected void Page_Load(object sender, EventArgs e)
{ if (!Page.IsPostBack) { 
} InitClientResource(); } private void InitClientResource() { string callBackStartScript = string.Empty; string callBackEndScript = string.Empty; callBackStartScript = "function callServer(arg,context) { " + Page.ClientScript.GetCallbackEventReference(this, "arg", "callEnd", "context") + "; } \r\nfunction getContext() { return document.getElementById('" + this.TextBox1.ClientID + "').value; } \r\n"; Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "callServer", callBackStartScript, true); callBackEndScript = "function callEnd(arg,context) { document.getElementById('ddd').innerText = arg;}"; Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "callEnd", callBackEndScript, true); Button1.OnClientClick = string.Format("callServer({0},'{1}'); return false;","getContext()" ,CALLBACK_PARAM); }
ICallbackEventHandler Members
}
Reference:
[1] http://msdn2.microsoft.com/en-us/library/ms178208.aspx;
[2] http://dotnet.sys-con.com/read/121828_p.htm
[3] http://staff.develop.com/ballen/blog/PermaLink.aspx?guid=c35c43f6-5686-40ee-9752-8095a848d821
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