Code
<asp:Image ID="Image1" runat="server" />
                <cc1:SlideShowExtender ID="Image1_SlideShowExtender" runat="server" 
                     Enabled="True"  
                     TargetControlID="Image1"  
                     ImageTitleLabelID="LabelName" 
                     NextButtonID="btnNext" 
                     PlayButtonID="btnAutoPlay" 
                     PreviousButtonID="btnPre" 
                     PlayButtonText="自动播放"
                     Loop="true" StopButtonText="停止" 
                     SlideShowServiceMethod="getImg"
                     ImageDescriptionLabelID="LabelDescription"  >
                </cc1:SlideShowExtender>

Code
<script type="text/C#" runat="server">
      [System.Web.Script.Services.ScriptMethod()]
      [System.Web.Services.WebMethod()]
      
      public static AjaxControlToolkit.Slide[] getImg()
      {
         
          
          List<picture> pics;
          dataAccess ds = new dataAccess();
          pics = ds.selectPicturesByAlbumId(1);
          Slide[] imgs=new Slide[pics.Count];
          
          for (int i = 0; i < pics.Count;i++ )
          {
              picture p = (picture)pics[i];
              imgs[i] = new Slide(p.url,p.name,p.description);
          }          
          
          return imgs;
          
      }