ADO.NET 对数据操作

public static class SQLHelper
    {
        static string connString = ConfigurationManager.ConnectionStrings["connString"].ToString();
        /// <summary>
        /// 执行增删改
        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public static int Update(string sql)
        {
            SqlConnection conn = new SqlConnection(connString);
            SqlCommand cmd = new SqlCommand(sql, conn);
            try
            {
                conn.Open();
                return cmd.ExecuteNonQuery();
            }
            catch (Exception ex)
            {
                throw new Exception(ex.Message);
            }
            finally
            {
                conn.Close();
            }
        }
        /// <summary>
        /// 执行单一结果查询
        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public static object GetSingleResult(string sql)
        {
            SqlConnection conn = new SqlConnection(connString);
            SqlCommand cmd = new SqlCommand(sql, conn);
            try
            {
                conn.Open();
                return cmd.ExecuteScalar();
            }
            catch (Exception ex)
            {
                throw new Exception(ex.Message);
            }
            finally
            {
                conn.Close();
            }
        }

        /// <summary>
        /// 执行一个结果集查询
        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public static SqlDataReader GetReader(string sql)
        {
            SqlConnection conn = new SqlConnection(connString);
            SqlCommand cmd = new SqlCommand(sql, conn);
            try
            {
                conn.Open();
                return cmd.ExecuteReader(CommandBehavior.CloseConnection);
            }
            catch (Exception ex)
            {
                conn.Close();
                throw new Exception(ex.Message);
            }
            finally
            {
                conn.Close();
            }
        }

        /// <summary>
        /// 执行返回数据集的查询
        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public static SqlDataAdapter GetDataSet(string sql)
        {
            SqlConnection conn = new SqlConnection(connString);
            SqlCommand cmd = new SqlCommand(sql, conn);
            //创建适配器对象
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            DataSet ds = new DataSet();

            try
            {
                conn.Open();
                da.Fill(ds);//使用数据适配器填充数据集
                return da;
            }
            catch (Exception ex)
            {
                throw new Exception(ex.Message);
            }
            finally
            {
                conn.Close();
            }
        }
    }