页面开发技巧

<% @ Page Language = " C# "  AutoEventWireup = " true "  EnableEventValidation = " false "  CodeFile = " CallBackEventHandler_cs.aspx.cs "  Inherits = " CallBackEventHandler_cs "   %>

<! 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 > Client CallBack </ title >
</ head >
< body >
< form id = " Form1 "  runat = " server " >

    < h3 > Cascading DropDownLists Using ICallBackEventHandler </ h3 >
    < asp:DropDownList ID = " ParentDropDown "
    onchange = " GetChildren(this.options[this.selectedIndex].value, 'ddl'); "    
    Runat = " server " >
      < asp:ListItem Text = " Item 1 "   />
      < asp:ListItem Text = " Item 2 "   />
      < asp:ListItem Text = " Item 3 "   />
    </ asp:DropDownList >
    < asp:DropDownList ID = " ChildDropDown "  AutoPostBack = " true "  style = " visibility:hidden "  Runat = " Server " >
     < asp:ListItem Text = " Child Item "   />
    </ asp:DropDownList >
    < br  />< br  />
    < asp:Label ID = " Label1 "  runat = " server " />

    < script type = " text/javascript " >

   function ClientCallback(result, context) {

      var childDropDown = document.forms[0].elements['<%=ChildDropDown.UniqueID%>'];

      if (!childDropDown){
         return;
      }

      childDropDown.length = 0;

      if (!result){
          return;
      }
      
      var rows = result.split('|'); 
      for (var i = 0; i < rows.length; ++i){
         var option = document.createElement("OPTION");
         option.value = rows[i];
         option.innerHTML = rows[i];     
         childDropDown.appendChild(option);
      }
      
      childDropDown.style.visibility = "visible";
   }

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

    </ script >

</ form >
</ body >

</ html >

// -----------------------------------------------------------------------
//   This file is part of the Microsoft .NET SDK Code Samples.
//  
//   Copyright (C) Microsoft Corporation.  All rights reserved.
//  
// This source code is intended only as a supplement to Microsoft
// Development Tools and/or on-line documentation.  See these other
// materials for detailed information regarding Microsoft code samples.
//  
// THIS CODE AND INFORMATION ARE PROVIDED AS IS WITHOUT WARRANTY OF ANY
// KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A
// PARTICULAR PURPOSE.
// -----------------------------------------------------------------------

using  System;
using  System.Web.UI;

public  partial  class  CallBackEventHandler_cs : System.Web.UI.Page, ICallbackEventHandler
{
    private string _callbackResult;

    private void Page_Load(object source, EventArgs e)
    {
        String callBack = Page.ClientScript.GetCallbackEventReference(this, "arg", "ClientCallback", "context", "ClientCallbackError", false);
        String clientFunction = "function GetChildren(arg, context){ " + callBack + "; }";
        Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "GetChildren", clientFunction, true);

        if (Page.IsPostBack && !Page.IsCallback)
        {
            Label1.Text = "You Selected: " + Request.Form["ParentDropDown"] + ": " + Request.Form["ChildDropDown"];
        }
    }

    public string GetCallbackResult()
    {        
        return _callbackResult;
    }

    public void RaiseCallbackEvent(string eventArgument)
    {
        switch (eventArgument)
        {
            case "Item 1":
                _callbackResult = "One|Two|Three";
                break;
            case "Item 2":
                _callbackResult = "Four|Five|Six";
                break;
            case "Item 3":
                _callbackResult = "Seven|Eight|Nine";
                break;
            default:
                _callbackResult = "";
                break;
        }
    }

}

    本文转自永春博客园博客，原文链接： http://www.cnblogs.com/firstyi/archive/2006/11/13/559156.html ，如需转载请自行联系原作者