public static class DbHelper    {        public static List
    
      GetData
     
      (string sql)        {            var connection = new SqlConnection(ConfigurationManager.ConnectionStrings["xxx"].ToString());            connection.Open();            SqlCommand command = connection.CreateCommand();            command.CommandText = sql;            command.CommandType = CommandType.Text;            var reader = command.ExecuteReader();            var list = GetList
      
       (reader);            command.Connection.Close();            return list;        }        private static List
       
         GetList
        
         (SqlDataReader reader)        {            var list = new List
         
          ();            while (reader.Read())            {                list.Add(Get
          
           (reader));            }            reader.Close();            reader.Dispose();            return list;        }        private static T Get
           
            (SqlDataReader reader)        {            var t = Activator.CreateInstance
            
             ();            var type = typeof(T);            foreach (var field in type.GetProperties())            {                var value = reader[field.Name] is DBNull ? null : reader[field.Name];                field.SetValue(t, value);            }            return t;        }     }