实体框架多表关系

Question

I have three tables

EVENT - PERSON - COMPANY

I need to have a relation many-to-many using those tables. An event can have one or more "clients",which can be either person or company. Normally, using no ORM, using sql , it would be something like :

EVENT
----
id
name

CLIENTEVENT
-----------
id 
clientid
clienttype -- person or company


PERSON
-----------
id 
name
lastname
...


COMPANY
-------
id
name

How does this approach can be replicated using entity framework? I am pretty new using EF so I would appreciate all help you can give me.I am using repository pattern, following this approach http://www.codeproject.com/Articles/838097/CRUD-Operations-Using-the-Generic-Repository-Pat .

Answer 1

I advice you instead of clientid and clienttype make another two columns: personID and companyID. Models will look this way:

public class Event     
{
    public int ID { get; set; }
    public string name { get; set; }

    public virtual ICollection<CLIENTEVENT> links { get; set; }
}

public class Company
{
    public int ID { get; set; }
    public string name { get; set; }

    public virtual ICollection<CLIENTEVENT> links { get; set; }
}

public class PERSON
{
    public int ID { get; set; }
    public string name { get; set; }
    public string lastname { get; set; }

    public virtual ICollection<CLIENTEVENT> links { get; set; }
}

public class CLIENTEVENT
{
    public int ID { get; set; }

    public virtual PERSON person { get; set; }
    public int? personID { get; set; }

    public virtual Company company { get; set; }
    public int? companyID { get; set; }

    public virtual Event event1 { get; set; }
    public int? event1ID { get; set; }
}

Answer 2

With EF Code First, you don't have to deal with joining tables like ClientEvent. You can simply write:

public class Event     
{
    public int Id { get; set; }

    public string Name { get; set; }

    public virtual ICollection<Company> Companies { get; set; }

    public virtual ICollection<Person> Persons { get; set; }
}

public class Company
{
    public int Id { get; set; }

    public string Name { get; set; }

    public virtual ICollection<Event> Events { get; set; }
}

public class Person
{
    public int ID { get; set; }

    public string Name { get; set; }

    public string Lastname { get; set; }

    public virtual ICollection<Event> Events { get; set; }
}

Try this code, you'll see EF creating two linking tables (EventPerson and EventCompany). Now, the client type is the collection you read ( someEvent.Persons or someEvent.Companies ), you can also easily get the events linked to a specific Person or a Company.

About many-to-many with EF .