Injecting Dependencies into Domain Model classes with Nhibernate (ASP.NET MVC + IOC)

Question

I\'m building an ASP.NET MVC application that uses a DDD (Domain Driven Design) approach with database access handled by NHibernate. I have domain model class (Administrator) th

Answer 1

You need to remember how it was hashed. This is so that you can hash a string in the future to check and see if it's their password, comparing that with the hashed value. That means that you need to store an enum or some other field in your object that indicates the hashing mechanism that was used in your database.

Otherwise, if you change your default hashing implementation, all of your old hashed passwords are no longer good, and your users will be left scratching their heads as to why their passwords no longer work--and you'll end up an IHashingService interface that provides no flexibility (since the hashing implementation cannot be changed without adding weird rules like "use this hash for Administrators created before 2010-01-12"), existing for no real good reason.

To that end, I would add the appropriate field (an enum, a string returned by the IHashingService interface, something) and either have NHibernate instantiate the hashing service for me via an IUserType implementation, or I'd use a factory pattern where the concrete instances were provided to the factory by the IoC container. This would be combining Jarrett's method-level injection with a solution that allows re-hydrated objects to find their hashing implementations without being dependent on the IoC container.

Good luck!