代码优先实体框架核心中的一对多一对一

Question

One company can have many addresses, however each company has a main address.

I am looking to find the best way to create this kind of relation in EF Core.

Below is what I came up with. Is there a better way? Am I way off entirely?

Models

public class Company
{
    public int Id { get; set; }

    public int MainAddressId { get; set; }
    public Address MainAddress { get; set; }

    public ICollection<CompanyAddress> CompanyAddresses { get; set; }

    // other company info
}

public class Address
{
    public int Id { get; set; }

    public int CompanyAddressId { get; set; }
    public CompanyAddress CompanyAddress { get; set; }

    // other address info
}

public class CompanyAddress
{
    public int CompanyId { get; set; }
    public Company Company { get; set; }

    public int AddressId { get; set; }
    public Address Address { get; set; }

    public bool IsMain { get; set; }
}

DataContext.cs

public class DataContext : DbContext
{
    public DataContext(DbContextOptions<DataContext> options) : base(options)
    {
    }

    public DbSet<Company> Companies { get; set; }
    public DbSet<Address> Addresses { get; set; }
    public DbSet<CompanyAddress> CompanyAddresses { get; set; }

    protected override void OnModelCreating(ModelBuilder builder)
    {
        builder.Entity<CompanyAddress>()
            .HasKey(ca => new {ca.CompanyId, ca.AddressId});

        builder.Entity<CompanyAddress>()
            .HasOne(ca => ca.Company)
            .WithMany(ca => ca.CompanyAddresses)
            .HasForeignKey(ca => ca.CompanyId)
            .OnDelete(DeleteBehavior.Cascade);

        builder.Entity<CompanyAddress>()
            .HasOne(ca => ca.Address)
            .WithOne(ca => ca.CompanyAddresses)
            .HasForeignKey(ca => ca.AddressId)
            .OnDelete(DeleteBehavior.Cascade);
    }
}

Answer 1

In my opinion, dead on. There are always other ways. But this is straight-forward and easily understood. MainAddress and MainAddressId are redundant. You don't have lazy loading (virtual) so you can easily determine the main address by

dbContext.Companies.FirstOrDefault(p => p.Id = <myCompanyId>);
dbContext.CompanyAddresses.FirstOrDefault(p => p.CompanyId == <myCompanyId> && p.IsMain);

If you go with lazy loading later, just add .Include("Address") to the second query. And yes, you can combine the two.