/// <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));
}