Specified key was too long; max key length is 767 bytes mysql

Specified key was too long; max key length is 767 bytes

说明: 执行当前 Web 请求期间，出现未经处理的异常。请检查堆栈跟踪信息，以了解有关该错误以及代码中导致错误的出处的详细信息。 

异常详细信息: MySql.Data.MySqlClient.MySqlException: Specified key was too long; max key length is 767 bytes

给Context增加如下的注解

[DbConfigurationType(typeof(MySql.Data.Entity.MySqlEFConfiguration))]
public class MyContext : DbContext
{ 
}