具有多对多关系生成表的实体框架

Question

Here's my question. I have 2 models (Person, Event) and with EF and modelbuilder I generate a booking table (with IdPerson and IdEvent as properties). So in my DB it's correct, I have 3 tables (Person, Event and Booking) with many to many relationship. But I have only 2 models in Visual Studio (Booking doesn't exist because of the self-generated table). With my Controller I want to write an action for the Person to suscribe to an event and I have to write on my table Booking on the DB but it doesn't exist as a model so I can't do that . How should I proceede? Should I create a Booking model and delete my modelbuilder?

Answer 1

I assume this is a model first approach.

The reason for having only 2 objects is that, by default, EF does not create objects for joint tables. What it does create is Navigation Property ( Entity Framework - Navigation Property Basics ). In one-to-many scenario, a navigation property inside a parent object contains a collection of entities in a foreign / child table. In many-to-many scenario, navigation properties of each entities will simply contain collections of its other entities.

Answer 2

When you are using ORMs like EF, you can sit back and let the ORM manage these middle tables.

You can use

person.Events.Add(event)

or

event.People.Add(event)

and EF handles all and inserts a row with personId and eventId in that table.

Here you can find a complete sample: http://blogs.msdn.com/b/wriju/archive/2011/05/14/code-first-ef-4-1-building-many-to-many-relationship.aspx