/// 
        /// 获取连接字符串        /// 
        private static readonly string constr = ConfigurationManager.ConnectionStrings["dbUser"].ConnectionString;        /// 
        /// 返回受影响行数（非查询语句）        /// 
        /// SQL语句        /// 参数化查询        /// 
             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();                }            }        }        /// 
        /// 返回查询结果集中的第一行第一列        /// 
        /// SQL语句        /// 参数化查询        /// 
             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();                }            }        }        /// 
        /// 返回查询结果有多条数据，数据放在数据库中        /// 
        /// SQL语句        /// 参数化查询        /// 
             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();                }            }        }        /// 
        /// 返回查询结果有多条数据，数据放在本地缓存中        /// 
        /// SQL语句        /// 参数化查询        /// 
             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];                }            }        }        /// 
        /// 将数据库中的Null转化为null        /// 
        ///         /// 
             public static object OutputNull(object value)        {            if (value == DBNull.Value)                return null;            else                return value;        }        /// 
        /// 将输入数据的null转化为数据库中Null        /// 
        ///         /// 
             public static object InputNull(object value)        {            if (value == null)                return DBNull.Value;            else                return value;        }    }