抛出异常

Question

   foreach (DataListItem dl in DataList1.Items)
调试时，到这里抛出异常了，

   CheckBox chk2;
    public void checkMenuID()
    {
        int id = Convert.ToInt32(Request["idd"]);
        var linq = (from b in dc.VM_CON_Article
                    where b.ArticleID == id
                    select b).FirstOrDefault();
        if (linq.ArticleShare == "")
        {
            bindName();
            //ShareMenu();
        }
        else
        {
            string[] powerList = linq.ArticleShare.Split(',');
            if (powerList.ToString() != null)
            {
                int num = linq.ArticleShare.Split(',').Length;
                for (int i = 0; i < num; i++)
                {
                    try
                    {
                        int lu = Convert.ToInt32(powerList[i]);
                        if (lu == 0)
                        {
                            return;
                        }
                        else
                        {
                            var sQuery = (from t in dc.VM_SYS_Menu
                                          where t.MenuID == lu
                                          select t).FirstOrDefault();
                            foreach (DataListItem dl in DataList1.Items)
                            {
                                chk2 = (CheckBox)(dl.FindControl("cbCheck"));
                                if (chk2 != null)
                                {
                                    chk2.Text = sQuery.MenuName;
                                    chk2.ID = powerList[i];
                                }
                                foreach (string item in powerList)
                                {
                                    if (item == null)
                                    {
                                        chk2.Checked = false;
                                    }
                                    else if (item == powerList[i])
                                    {
                                        chk2.Checked = true;
                                    }
                                    else
                                    {
                                        bindName();
                                        ShareMenu();
                                    }
                                }
                            }
                        }
                    }
                    catch (Exception ex)
                    {
                        throw ex;
                    }
                }
            }
        }
    }