学步园

用DataReader读取数据怎样判断当前记录的某列是否为空 ：

        //调用：
        if (ReaderExists(dr, "Log_ID"))
            model.Log_DoctorID = GetInt(dr["Log_ID"]);

        /// <summary>
        /// 判断 DataReader 里面是否包含指定的列
        /// </summary>
        /// <param name="dr"></param>
        /// <param name="columnName"></param>
        /// <returns></returns>
        public static bool ReaderExists(DbDataReader dr, string columnName)
        {
            int count = dr.FieldCount;
            for (int i = 0; i < count; i++)
            {
                if (dr.GetName(i).Equals(columnName))
                {
                    return true;
                }
            }
            return false;
        }

        /// <summary>
        /// 判断 DataReader 里面是否包含指定的列
        /// </summary>
        /// <param name="dr"></param>
        /// <param name="columnName"></param>
        /// <returns></returns>
        public static bool ReaderExists2(DbDataReader dr, string columnName)
        {
            dr.GetSchemaTable().DefaultView.RowFilter = "ColumnName= '" + columnName + "'";
            return (dr.GetSchemaTable().DefaultView.Count > 0);
        }
      

推荐使用第一种方式，基本不存在性能损耗