SQLHelper

　　　　 /// <summary>

        /// 获取连接字符串

        /// </summary>

        private static readonly string constr = ConfigurationManager.ConnectionStrings["dbUser"].ConnectionString;



        /// <summary>

        /// 返回受影响行数（非查询语句）

        /// </summary>

        /// <param name="sql">SQL语句</param>

        /// <param name="parameters">参数化查询</param>

        /// <returns></returns>

        public static int ExecuteNonQuery(string sql, params SqlParameter[] parameters)

        {

            using (SqlConnection conn = new SqlConnection(constr))

            {

                conn.Open();

                using (SqlCommand cmd = conn.CreateCommand())

                {

                    cmd.CommandText = sql;

                    cmd.Parameters.AddRange(parameters);

                    return cmd.ExecuteNonQuery();

                }

            }

        }



        /// <summary>

        /// 返回查询结果集中的第一行第一列

        /// </summary>

        /// <param name="sql">SQL语句</param>

        /// <param name="parameters">参数化查询</param>

        /// <returns></returns>

        public static object ExecuteScalar(string sql, params SqlParameter[] parameters)

        {

            using (SqlConnection conn = new SqlConnection(constr))

            {

                conn.Open();

                using (SqlCommand cmd = conn.CreateCommand())

                {

                    cmd.CommandText = sql;

                    cmd.Parameters.AddRange(parameters);

                    return cmd.ExecuteScalar();

                }

            }

        }



        /// <summary>

        /// 返回查询结果有多条数据，数据放在数据库中

        /// </summary>

        /// <param name="sql">SQL语句</param>

        /// <param name="parameters">参数化查询</param>

        /// <returns></returns>

        public static SqlDataReader ExecuteReader(string sql, params SqlParameter[] parameters)

        {

            using (SqlConnection conn = new SqlConnection())

            {

                conn.Open();

                using (SqlCommand cmd = conn.CreateCommand())

                {

                    cmd.CommandText = sql;

                    cmd.Parameters.AddRange(parameters);

                    return cmd.ExecuteReader();

                }

            }

        }



        /// <summary>

        /// 返回查询结果有多条数据，数据放在本地缓存中

        /// </summary>

        /// <param name="sql">SQL语句</param>

        /// <param name="parameters">参数化查询</param>

        /// <returns></returns>

        public static DataTable ExecuteDataSet(string sql, params SqlParameter[] parameters)

        {

            using (SqlConnection conn = new SqlConnection(constr))

            {
　　　　　　　　　 conn.Open()

                using (SqlCommand cmd = conn.CreateCommand())

                {

                    cmd.CommandText = sql;

                    cmd.Parameters.AddRange(parameters);



                    DataSet dataset = new DataSet();

                    SqlDataAdapter adapter = new SqlDataAdapter(cmd);

                    adapter.Fill(dataset);

                    return dataset.Tables[0];

                }

            }

        }



        /// <summary>

        /// 将数据库中的Null转化为null

        /// </summary>

        /// <param name="value"></param>

        /// <returns></returns>

        public static object OutputNull(object value)

        {

            if (value == DBNull.Value)

                return null;

            else

                return value;

        }



        /// <summary>

        /// 将输入数据的null转化为数据库中Null

        /// </summary>

        /// <param name="value"></param>

        /// <returns></returns>

        public static object InputNull(object value)

        {

            if (value == null)

                return DBNull.Value;

            else

                return value;

        }



    }