实体框架平行一对多关系

Question

I've been looking around to try to create a parallel one-to-many relationship in EF. Heres what I mean:

I've got two classes, Transaction and User:

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

    public string ExecutorID { get; set; }
    public virtual User Executor { get; set; }

    public string ConsumerID { get; set; }
    public virtual User Consumer { get; set; }
}

public class User
{
    public UserRole Role { get; set; }
    public string Name { get; set; }

    public string Id { get; set; }
    public string Pin { get; set; }

    public virtual List<Transaction> ExecutedTransactions { get; set; }
    public virtual List<Transaction> Transactions { get; set; } 
}

If you haven't seen it already, I've got two links between the objects, Transactions and Executed Transactions . My question is how can I tell EF to differentiate between the two?

Transactions should point to all Transaction where User.ID == Transaction.ConsumerID and ExecutedTransactions where User.ID == Transaction.ExecutorID

Answer 1

Here are the classes where Food and Book are derived from Item .

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<Food> Foods { get; set; }
    public ICollection<Book> Books { get; set; }
}
public abstract class Item
{
    public int Id { get; set; }
    public string Name { get; set; }
}
public class Food : Item
{
    public int CookedById { get; set; }
    [ForeignKey("CookedById")]
    public Person CookedBy { get; set; }
}
public class Book : Item
{
    public int AuthorId { get; set; }
    [ForeignKey("AuthorId")]
    public Person Author { get; set; }
}

Option A Table Per Hierarchy

public class AppContext : DbContext
{
    public DbSet<Person> People { get; set; }
    public DbSet<Item> Items { get; set; }
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Person>().HasMany(p => p.Foods).WithRequired(f => f.CookedBy).WillCascadeOnDelete(false);
    }
}

Result would be 2 tables , table Person and Item that has automatically Discriminator column that will be filled with Food and Book .

To query you need to filter from Items by its type.

using (var context = new AppContext())
{
    var foods = context.Items.Where(item => item is Food).ToArray();
    var books = context.Items.Where(item => item is Book).ToArray();
}

Option B Table Per Concrete Class

public class AppContext : DbContext
{
    public DbSet<Person> People { get; set; }
    public DbSet<Food> Foods { get; set; }
    public DbSet<Book> Books { get; set; }
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Person>().HasMany(p => p.Foods).WithRequired(f => f.CookedBy).WillCascadeOnDelete(false);
    }
}

Result would be 3 tables , table Person , Food and Book .

To query you can directly take from Foods and Books.

using (var context = new AppContext())
{
    var foods = context.Foods.ToArray();
    var books = context.Books.ToArray();
}

Option C Table Per Type

public class AppContext : DbContext
{
    public DbSet<Person> People { get; set; }
    public DbSet<Item> Items { get; set; }
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Person>().HasMany(p => p.Foods).WithRequired(f => f.CookedBy).WillCascadeOnDelete(false);
        modelBuilder.Entity<Food>().ToTable("Foods");
        modelBuilder.Entity<Book>().ToTable("Books");
    }
}

Result would be 4 Tables , table Person , Item , Food and Book . Table Food and Book will have relationship to table Ttem .

The query is the same like Table Per Hierarchy.