ICallbackEventHandler:回调函数的实现(备忘)

示例来自：ASP.NET 2.0编程珠玑

服务器端：

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;

//继承ICallbackEventHandler，确保使用客户回调特性时，回调事件在会送过程中处理

public partial class Chapter4_Demo4 : System.Web.UI.Page,System.Web.UI.ICallbackEventHandler
{
protected void Page_Load(object sender, EventArgs e)
{

　　　//检查用户的浏览器是否支持回调特性
        if (!Request.Browser.SupportsCallback)
        {
            throw new ApplicationException("This browser doesn't support Client callbacks.");
        }

　　 //获取回调事件的引用

        string src = Page.ClientScript.GetCallbackEventReference(this, "arg", "ClientCallback", "ctx", "ClientErrorCallback", false);
        string mainSrc = @"function ValidateNumber(arg,ctx)
                                   { " + src + ";}";
        Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "ValidateNumber", mainSrc, true);
    }

private string _returnFormServer;

　 //eventArgs表示客户端方法中的数据

    public void RaiseCallbackEvent(string eventArgs)
    {
        try
        {
            int value = Int32.Parse(eventArgs);

            if (value >= 1 && value <= 1000)
            {
                this._returnFormServer = "You entered the number: " + eventArgs;
            }
            else
            {
                this._returnFormServer = "Please enter a number between 1 and 1000";
            }
        }
        catch
        {
            throw new ApplicationException("You must enter a number.");
        }
    }

　//给客户端返回一个字符串，返回值作为一个参数传送给客户端的回调方法

    public string GetCallbackResult()
    {
        return this._returnFormServer;
    }
}

客户端：

<html>
<head runat="server">
    <title>Untitled Page</title>
    <script language=javascript>
        function Validate()
        {
            var n = document.forms[0].txtNumber.value;
            ValidateNumber(n,"txtNumber");
        }

        function ClientCallback(result,context)
        {
            alert(result);
            alert(context);
        }

        function ClientErrorCallback(error,context)
        {
            alert("The validation failed. " + error);
        }
    </script>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        Please enter a number between 1 and 1000:<br />
        <input id="txtNumber" name="txtNumber" type=text />
        <button id="btnValidate" onclick="Validate()">Validate</button>
    </div>
    </form>
</body>
</html>

作者：冰碟
出处：http://www.cnblogs.com/icebutterfly/
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