check if the item's value on the list

using (SparkDataContext Data = new SparkDataContext()) { Guid user_id = new Guid ( Membership.GetUser(HttpContext.Current.User.Identity.Name).ProviderUserKey.ToString()); //Guid user_id = (Guid)Membership.GetUser(HttpContext.Current.User.Identity.Name).ProviderUserKey; List<SPGetModulesFromUserIDResult> SPGetModulesFromUserIDResult = Data.SPGetModulesFromUserID(user_id).ToList(); GridView1.DataSource = SPGetModulesFromUserIDResult; GridView1.DataBind(); string YrStr = ""; for (int i = 0; i < CheckBoxList1.Items.Count; i++) if (CheckBoxList1.Items[i].Value in (SPGetModulesFromUserIDResult.All) ) { CheckBoxList1.Items[i].Selected=true; } } i need to check if the item value on the list, it ...