实体框架6关系

Question

Tools Used:

WPF .Net 4.5
MySQL - Lastest version
Visual Studio 2013 Community Edition

Problem

Hi,

I'm having trouble mapping the POCO objects to the existing database where I have a base class that contains an ID property that is inherited by all model classes.

The base class itself is ignored in the context's OnModelCreating method and the problem starts when I try to specify the relationship between User and Session.

The tables are as follows:

====================
User
====================
ID | Name | Password
====================


====================
Session
====================
ID | Password | User
====================

The third column "User" in the session table, contains the user ID, so normally I could join the user table to the session table with plain old SQL.

All the examples I saw on the web involves creating a navigational property, first problem with that, it creates circular references which creates headaches when you try to serialize the object, and serialization is used to communicate between the client and the server.

The second problem is that this is a toy example of a much bigger system, the objects would get polluted with lots of properties.

Is this example, the session object knows about the user but user does not know about his session. So far i tried to map the session with the following:

public
class SessionMap : EntityTypeConfiguration <Session>
{
    public
    SessãoMap ()
    {
        /**
         * Table.
         */
        this.ToTable ("Session");

        /**
         * Primary key.
         */
        this.HasKey (a => a.ID);

        /**
         * Columns.
         */
        this.Property (a => a.ID      );
        this.Property (a => a.Password);

        this.HasRequired (a => a.User)
            .WithMany    ();
    }
}

But as you can see, I'm not specifying the foreign key and it gives the following error when I try to save a session object:

Unknown column 'User_ID' in 'field list'

Which makes sense but how do I solve this? :s

Reference Code

public
abstract
class Base
{
    public Int64 ID {get;set;}
}

public
class User : Base
{
    public String Name     {get;set;}
    public String Password {get;set;}
}

public
class Session : Base
{
    public String Password {get;set;}
    public User   User     {get;set;}
}

public
class Context : DbContext
{
    public DbSet <Session> Sessions {get;set;}
    public DbSet <User>    Users    {get;set;}

    public
    Context () : base ("name=MySQLConnectionString")
    {
    }

    protected
    override
    void OnModelCreating (DbModelBuilder Builder)
    {
        base.OnModelCreating (Builder);

        Builder.Ignore <Base> ();

        Builder.Configurations.Add (new Mapping.SessionMap ());
        Builder.Configurations.Add (new Mapping.UserMap    ());
    }
}

Answer 1

Found the answer.

In the session table, I changed the "User" column to "UserID" and then in the SessionMap class I did the following:

this.HasRequired (a => a.User)
    .WithMany    ()
    .Map         (m => m.MapKey ("UserID"));