Model backing a DB Context has changed; Consider Code First Migrations

　　Model增加一个字段，数据库对应的也手动添加了字段但是运行时报错

　　The model backing the 'TopLogDbContext' context has changed since the database was created. Consider using Code First Migrations to 　　　　update the database 

　　参考原文：Model backing a DB Context has changed; Consider Code First Migrations