从webservice读取string[]至downlist，增加onchange事件，更改相关显示。

aspx页面

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default2.aspx.cs" Inherits="Default2" %>

<!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>Untitled Page</title>

function Button1_onclick() {

WebService.getStr(callComplete);

}

function aa()

{

var List = document.getElementById("dd1");

document.getElementById("Label1").innerHTML = List.options[List.selectedIndex].value;

}

function callComplete(result)

{

var List = document.getElementById("dd1");

for (x=List.options.length-1; x > -1; x--)

{

List.remove(0);

}

for(x=0;x<result.length;x++)

{

var option = document.createElement("option");

option.text = result[x];

option.value = result[x];

if ( window.navigator.appName.toLowerCase().indexOf("microsoft") > -1)

List.add(option);

else

List.add(option, null);

}

</script>

</head>
<body>
    <form id="form1" runat="server">
        <asp:ScriptManager ID="ScriptManager1" runat="server">
            <Services>
                <asp:ServiceReference Path="WebService.asmx" />
            </Services>
        </asp:ScriptManager>
        <input id="Button1" type="button" value="button" language="javascript" onclick="return Button1_onclick()" />
        <asp:DropDownList ID="dd1" runat="server">
        </asp:DropDownList>
        <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
    </form>
</body>
</html>

webservice代码：

using System;
using System.Web;
using System.Collections;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.Web.Script.Services;
using System.Data;

/// <summary>
/// WebService 的摘要说明
/// </summary>
///
[ScriptService]
[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
public class WebService : System.Web.Services.WebService {

    public WebService () {

        //如果使用设计的组件，请取消注释以下行
        //InitializeComponent();
    }

    [WebMethod]
    public string HelloWorld() {
        return "Hello World";
    }

    [WebMethod]
    public string [] getStr()
    {

        return new  string[]  {"Hello World","bbb","cccc"};
    }