private void generdownclass(downclass downclass)
    {
        StringBuilder sb = new StringBuilder();
        generSB(downclass.id, downclass.classname, sb);
        List<downclass> nclist = dlogic.GetList(downclass.id);
        foreach (downclass item in nclist)
        {
            generSB(item.id, item.classname, sb, false);

        }
        OutStr = sb.ToString();
    }
    public string getDownNav()
    {
        string res = string.Empty;
        string lb = Request.QueryString.Get("sid");
        string newsid = Request.QueryString.Get("id");
        downloadManager mgr = new downloadManager();

        if (!string.IsNullOrEmpty(newsid))
        {
            WhereClip where = new WhereClip();
            where = where && download._.id == newsid;
            download model = new download();
            model = mgr.GetdownloadItemById(where);
            if (model != null)
            {
                lb = model.sid.ToString();
            }
        }
        if (!string.IsNullOrEmpty(lb))
        {
            downclass modelclass = new downclass();
            WhereClip where2 = new WhereClip();
            where2 = where2 && downclass._.id == lb;
            modelclass = mgr.GetItemById(where2);
            res = string.Format(@"<a href='Category.aspx?type=download'>下载中心</a>&nbsp;&gt;&nbsp;&nbsp;<a href='Category.aspx?sid={0}&type=download'>{1}</a>", modelclass.id, modelclass.classname);
        }
        else
        {
            res = "<a href='Category.aspx?type=download'>下载中心</a>";
        }
        return res;
    }