How to add 2 Foreign Key on one database table using ASP.NET Core and Angular

Question

'

I have 2 database tables:

1. College
2. Course

Now I want to create an additional table for CollegeCourses but it should have also 2 foreign keys from College and Course table.

If I want one foreign key on a table then I can do like this:

modelBuilder.Entity<Course>().OwnsMany(f => f.CollegeCourses);

I'm not sure on what to do if I try to add two foreign keys in one table.

I tried this one but it didn't work, it creates another table instead of just CollegeCourses:

modelBuilder.Entity<College>().OwnsMany(f => f.CollegeCourses);
modelBuilder.Entity<Course>().OwnsMany(f => f.CollegeCourses);

SOLVED: Thanks for the help guys!

I found this on the link provided by @Hassan: Fluent API, many-to-many in Entity Framework Core '

I'm a bit confused on why there are two foreign key as a primary key on a table. How do I get those data without an Id holding them?

And I created a sample based on the code above but the difference is that I added a variable Id as my primary key.

modelBuilder.Entity<CollegeCourse>().HasKey(pc => new { pc.Id });

  modelBuilder.Entity<CollegeCourse>()
                .HasOne(pc => pc.College)
                .WithMany(p => p.CollegeCourses)
                .HasForeignKey(pc => pc.CollegeId);

  modelBuilder.Entity<CollegeCourse>()
                .HasOne(pc => pc.Course)
                .WithMany(c => c.CollegeCourses)
                .HasForeignKey(pc => pc.CourseId);

The database sample table look like this:

Answer 1

You must change delete behavior of one foreign key to Restrict. I create example: First create your classes:

public class Customer
{
    public string Id { get; set; }
    public string Address1 { get; set; }
    public string Address2 { get; set; }
    public string ZipCode1 { get; set; }
    public string ZipCode2 { get; set; }

    public City City1 { get; set; }
    public City City2 { get; set; }
}



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

    public List<Customer> Customers1 { get; set; }
    public List<Customer> Customers2 { get; set; }
}

Next create Mapped class:

public class CustomerMap : IEntityTypeConfiguration<Customer>
{
    public void Configure(EntityTypeBuilder<Customer> builder)
    {
        builder.HasKey(k => k.Id);
        builder
            .HasOne(c => c.City1)
            .WithMany(c => c.Customers1);
        builder
            .HasOne(c => c.City2)
            .WithMany(c => c.Customers2).OnDelete(DeleteBehavior.Restrict);
    }
}

And for end override OnModelCreating method in DbContext

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    base.OnModelCreating(modelBuilder);
    modelBuilder.ApplyConfiguration(new CustomerMap());
}