怕忘了 后天就比赛了 存着随时看下

//查询数据集
        public DataSet Query(string sqlStr)
        {
            using (SqlConnection conn = new SqlConnection(constr))
            {
                using (SqlDataAdapter ada = new SqlDataAdapter(sqlStr, conn))
                {
                        conn.Open();
                        DataSet ds = new DataSet();
                        ada.Fill(ds);
                        return ds;
                }
            }
        }
        //查询datatable
        public DataTable GetQueryData(string sqlStr)
        {
            DataSet ds = Query(sqlStr);
            if (ds != null && ds.Tables.Count > 0)
                return ds.Tables[0];
            return null;
        }
        //单个查询返回string
        public string GetSingle(string sqlStr)
        {
            using (SqlConnection conn = new SqlConnection(constr))
            {
                SqlCommand cmd = new SqlCommand(sqlStr, conn);
                conn.Open();
                return String.Format("{0}", cmd.ExecuteScalar());
            }
        }