EntityFramework anonymous composite key property n

问题:

I'm using EntityFramework 5 (or 4.3 for .Net Framework 4.0)

In my DbContext object I have already set the correct DbSets and the objects contain proper references to each other. This is not new for me, and things are working well.

Now in this case I have some composite keys that, sometimes, include the foreign key of a table (or object in this case). For this I use the HasKey<>() function on the OnModelCreating method of the DbContext. When these properties have different names, there is no problem, but when these properties have the same name, the migration cannot be done.

An example:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        // ...

        modelBuilder.Entity<PatientVisit>().ToTable("PatientVisits");
        modelBuilder.Entity<PatientVisit>().HasKey(x => 
            new { x.Patient.Code, x.Code });

        // ...

        base.OnModelCreating(modelBuilder);
    }

As you can see in the code provided, the object PatientVisit has a property named Code, but this property can be repeated as long as it is repeated with a different patient. The entity Patient also has a key defined named Code.

An anonymous type cannot have two properties inferring the same name (obvious). The typical solution would be to name the properties of the anonymous type like this:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        // ...

        modelBuilder.Entity<PatientVisit>().ToTable("PatientVisits");
        modelBuilder.Entity<PatientVisit>().HasKey(x => 
            new { PatientCode = x.Patient.Code, VisitCode = x.Code });

        // ...

        base.OnModelCreating(modelBuilder);
    }

But doing this, when I try to add a migration this error message is thrown.

The properties expression 'x => new <>f__AnonymousType3`2(PatientCode 
= x.Patient.Code, VisitCode = x.Code)' is not valid. The expression 
should represent a property: C#: 't => t.MyProperty'  VB.Net: 'Function(t)
t.MyProperty'. When specifying multiple properties use an anonymous 
type: C#: 't => new { t.MyProperty1, t.MyProperty2 }'  
VB.Net: 'Function(t) New With { t.MyProperty1, t.MyProperty2 }'.

回答1:

I think what you need to do here is give PatientVisit a new property PatientCode. Which would be the foreign key to Patient. E.g

    HasRequired<PatientVisit>(v => v.Patient).WithMany()
                                             .HasForeignKey(v => v.PatientCode)

Then you can do

    modelBuilder.Entity<PatientVisit>().HasKey(x => 
        new { x.PatientCode, x.Code });