How do I enforce an either-or relationship between model properties, using EF Core?

Question

I'm using EF Core.

My Customer entity has properties Address1, Address2, and AddressFull.

Depending on which system sends me the data, I may receive Address1 and Address2, or I may receive AddressFull.

So I need:

• EITHER Address1 and Address2 required, and AddressFull not-required
• OR Address1 and Address2 not-required, and AddressFull required

So I have:

  entityTypeBuilder.Property(p => p.Address1).IsRequired(false);
  entityTypeBuilder.Property(p => p.Address2).IsRequired(false);
  entityTypeBuilder.Property(p => p.AddressFull).IsRequired(false);

But this config does not properly map to my domain, and I want to enforce the logic. Is that possible in EF Core?

Answer 1

You need to allow for your DbContext different mapping according to your scenario, you can check this answer to enable in your DbContext change the mapping:

Dynamically changing schema in Entity Framework Core

Answer 2

In general, there are two ways to implement this type of complex domain logic. You can do it in the database using CHECK constraints or triggers, or you can do it in your domain objects and check them during SaveChanges. Here is an example of the latter.

class MyEntity : IValidatableObject
{
    public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
    {
        if (string.IsNullOrEmpty(Address1)
            && string.IsNullOrEmpty(Address2)
            && string.IsNullOrEmpty(AddressFull))
        {
            yield return new ValidationResult("An address is required.");
        }
    }
}

class MyContext : DbContext
{
    public override int SaveChanges()
    {
        var entities = from e in ChangeTracker.Entries()
                       where e.State == EntityState.Added
                           || e.State == EntityState.Modified
                       select e.Entity;
        foreach (var entity in entities)
        {
            var validationContext = new ValidationContext(entity);
            Validator.ValidateObject(
                entity,
                validationContext,
                validateAllProperties: true);
        }

        return base.SaveChanges();
    }
}