这段代码错在哪了？困惑

我把代码全贴出来，就是要实现数据表里的图片幻灯播放，select控件中绑定数据表里的PicName字段，我想在播放图片时把图片名称也显示出来（随图片变化图片名称在Select1控件中变化，比如img1控件中显示图片200905252300_L.jpg时，Select1控件中就显示200905252300_L,img1控件中显示图片200905252330_L.jpg时，Select1控件中就显示200905252330_L,依次类推）请大家帮我看一看哪里有问题，这个问题困扰好久了。 
controlpic.js文件 Type.registerNamespace("Demo"); Demo.SlideShow=function() 
{ 
    this._slides=new Array(); 
    this._delay=2000; 
    this._currentIndex=0; 
    this._pause=false; 
} Demo.SlideShow.prototype= 
{ 
    get_Slides:function() 
    { 
        return this._slides; 
    }, 
    
    set_Slides:function(value) 
    { 
        this._slides=value; 
    }, 
    
    get_Delay:function() 
    { 
        return this._delay; 
    }, 
    
    set_Delay:function(value) 
    { 
        this._delay=value; 
    }, 
    
    get_CurrentIndex:function() 
    { 
        return this._currentIndex; 
    }, 
    
    set_CurrentIndex:function(value) 
    { 
        if(value <0) 
        { 
            this._currentIndex=this._slides.length-1; 
            return; 
        } 
        if(value>=this._slides.length) 
        { 
            this._currentIndex=0; 
        } 
        else 
        { 
            this._currentIndex=value; 
        } 
    }, 
    
    get_IsPaused:function() 
    { 
        return this._pause; 
    }, 
    
    set_IsPaused:function(value) 
    { 
        this.pause=value; 
    }, 
    
    Pause:function() 
    { 
        this._pause=true; 
    }, 
    
    Play:function() 
    { 
        this._pause=false; 
        window.setTimeout("slideshow.ShowImage()", 
    this.get_Delay()); 
    }, 
    
    ShowFirst:function() 
    { 
        this._currentIndex=0; 
        this.ShowImage(); 
        
    }, 
    
    ShowLast:function() 
    { 
        this._currentIndex=this._slides.length-1; 
        this.ShowImage(); 
    }, 
    
    ShowNext:function() 
    { 
        var newIndex=this._currentIndex +1; 
        this.set_CurrentIndex(newIndex); 
        this.ShowImage(); 
    }, 
    
    ShowPrevious:function() 
    { 
        var newIndex=this._currentIndex -1; 
        this.set_CurrentIndex(newIndex); 
        this.ShowImage(); 
    }, 
    //显示图片 
    ShowImage:function() 
    { 
      var img=$get("Image1"); 
      var Select=$get("Select1"); 
    if(img.style.visibility=="hidden") 
    { 
    img.style.visibility="visible"; 
    } 
        var slides=this.get_Slides(); 
        var curIndex=this.get_CurrentIndex(); 
        img.src=slides[curIndex];  
        $get("Select1").selectedIndex = curIndex; 
        if(this.get_IsPaused()==false) 
        { 
            this.set_CurrentIndex(curIndex+1); 
            this.Play(); 
        } 
        setSelect(curIndex) 
    } 
} function setSelect(curIndex) 
{ 
var obj=document.getElementById("Select1") 
obj.options[curIndex].selected=1 
} 
Demo.SlideShow.registerClass("Demo.SlideShow"); var slideshow=new Demo.SlideShow(); 
页面设计文件Default.aspx如下： 
<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="_Default" %> <%@ Register Assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" 
    Namespace="System.Web.UI" TagPrefix="asp" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" > 
<head id="Head1" runat="server"> 
    <title>Untitled Page </title> 
    <script type="text/javascript"> 
function pageLoad() 
{ 
    var img=$get("Image1"); 
    var Select=$get("Select1"); 
    img.style.visibility="hidden"; 
    Select.style.visibility=="hidden" 
    PageMethods.GetSlides(OnSuccess,OnError,OnTimeOut); 
} 
        
function OnSuccess(result) 
{ 
    slideshow.set_Slides(result); 
    slideshow.set_Delay(2000); 
    slideshow.Play(); 
} 
        
function OnError(result) 
{ 
    alert(result.get_message()); 
} function OnTimeOut(result) 
{ 
    alert(result); 
} 
</script> 
</head> 
<body> 
    <form id="form1" runat="server"> 
    <div> 
        <asp:ScriptManager ID="ScriptManager1" runat="server" EnablePageMethods="True" AsyncPostBackTimeout="1000"> 
            <Scripts> 
                <asp:ScriptReference Path="~/controlpic.js" /> 
            </Scripts>         </asp:ScriptManager> 
    
    </div> 
        <table style="width: 497px" border="1"> 
            <tr> 
                <td style="width: 505px; height: 383px;"> 
                    <img width="500" id="Image1" height="375"/> 
</td> 
            </tr> 
            
            <tr> 
            <td style="text-align: center; width: 505px;"> 
                &nbsp; <select id="Select1" style="width: 114px"> 
                    <option selected="selected"> </option> 
                </select> </td> 
            </tr> 
            <tr> 
                <td style="width: 505px; height: 74px;"> 
                    &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 
                    <input id="Button1" type="button" value=" < <" onclick="slideshow.ShowFirst()" style="width:50px" /> 
                    <input id="Button2" type="button" value=" <" onclick="slideshow.ShowPrevious()" style="width:50px"/> 
                    <input id="Button3" type="button" value="||" onclick="slideshow.Pause()" style="width:50px"/> 
                    <input id="Button4" type="button" value="play" onclick="slideshow.Play()" style="width:50px"/> 
                    <input id="Button5" type="button" value=">" onclick="slideshow.ShowNext()" style="width:50px"/> 
                    <input id="Button6" type="button" value=">>" onclick="slideshow.ShowLast()" style="width:50px"/> </td> 
            </tr> 
        </table> 
    </form> 
</body> 
</html> 
我的Default.aspx.cs文件是： 
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; 
using System.Web.Services; 
using System.Data.SqlClient; public partial class _Default : System.Web.UI.Page 
{ 
    protected void Page_Load(object sender, EventArgs e) 
    { 
      
    } 
    [WebMethod] 
    public static string[] GetSlides() 
    { 
        SqlConnection SqlCon = new SqlConnection(ConfigurationManager.AppSettings["ConSql"]); 
        SqlCon.Open(); 
        string StrSql = "select PicPath,PicName from PicCloud"; 
        SqlDataAdapter Sda = new SqlDataAdapter(StrSql, SqlCon); 
        DataSet Ds = new DataSet(); 
        Sda.Fill(Ds); 
        string[] slides = new string[Ds.Tables[0].Rows.Count]; 
        for (int i = 0; i < Ds.Tables[0].Rows.Count; i++) 
        { 
            slides[i] = Ds.Tables[0].Rows[i][0].ToString().Trim(); 
        } 
        return slides; 
    } 
} 
数据表结构是： 
PicId    PicPath                PicName 
1    images/200905252300_L.jpg    200905252300_L 
2    images/200905252330_L.jpg    200905252330_L 
3    images/200905260030_L.jpg    200905260030_L 
4    images/200905260100_L.jpg    200905260100_L