/// <summary>
 ///     判断是否存在某表的某个字段
 /// </summary>
 /// <param name="tableName">表名称</param>
 /// <param name="columnName">列名称</param>
 /// <returns>是否存在</returns>
 public bool ColumnExists(string tableName, string columnName)
 {
     return(_db.ColumnExists(tableName, columnName));
 }