EF6一对一或零关系（Fluent API）

Question

I have such classes (simplicified):

public class Transaction
{
    public int LocalId { get; set; }
    public int MachineId { get; set; }
    public virtual Machine Machine { get; set; }       
    public int? MoneyId { get; set; }
    public virtual TransactionMoney Money { get; set; }
}

public class Machine
{
    public int Id { get; set; }
    public string Name { get; set; }
}

public class TransactionMoney
{
    public int LocalId { get; set; }
    public int MachineId { get; set; }
    public virtual Machine Machine { get; set; }
    public int TransactionId { get; set; }
    public virtual Transaction Transaction { get; set; }
}

I would like to have relationship Transaction 1 <-> 0...1 TransactionMoney where foreign key in Money should be TransactionId and MachineId (connected to transaction's LocalId and MachineId). I need to do this in fluent API.

What I've tried is:

    modelBuilder.Entity<Transaction>()
                .HasOptional(t => t.Money)
                .WithRequired(t => t.Transaction)
                .HasForeignKey() <--- there is no such method

and in other side

modelBuilder.Entity<TransactionMoney>()
    .HasRequired(t => t.Transaction)
    .WithOptional(t => t.Money)
            .HasForeignKey() <--- there is no such method

Answer 1

You can use something like this

modelBuilder.Entity<TransactionMoney>()
    .HasRequired(t => t.Transaction)
    .WithOptional(t => t.Money)
    .Map(a => a.MapKey("TransactionId", "MachineId"));

It turns out that the design you are targeting cannot be done in EF. The closest I was able to get is as follows. But before I go, there are some things to note. MoneyId field is removed from Transaction . LocalId field is removed from TransactionMoney . Foreign key is specified with data annotation. If any of those is unacceptable, just skip the rest.

Entities:

public class Transaction
{
    public int LocalId { get; set; }
    public int MachineId { get; set; }
    public virtual Machine Machine { get; set; }
    public virtual TransactionMoney Money { get; set; }
}

public class Machine
{
    public int Id { get; set; }
    public string Name { get; set; }
    public virtual ICollection<Transaction> Transactions { get; set; }
    public virtual ICollection<TransactionMoney> Money { get; set; }
}

public class TransactionMoney
{
    public int MachineId { get; set; }
    public virtual Machine Machine { get; set; }
    public int TransactionId { get; set; }
    [ForeignKey("TransactionId,MachineId")]
    public virtual Transaction Transaction { get; set; }
}

Configuration

modelBuilder.Entity<Transaction>()
    .HasKey(t => new { t.LocalId, t.MachineId })
    .HasRequired(t => t.Machine)
    .WithMany(t => t.Transactions)
    .HasForeignKey(t => t.MachineId);

modelBuilder.Entity<TransactionMoney>()
    .HasRequired(t => t.Machine)
    .WithMany(t => t.Money)
    .HasForeignKey(t => t.MachineId);

modelBuilder.Entity<TransactionMoney>()
    .HasKey(t => new { t.TransactionId, t.MachineId })
    .HasRequired(t => t.Transaction)
    .WithOptional(t => t.Money);