Generate a composite unique constraint/index, in EF Core

Question

I need a composite unique constraint for my entity's Name property, which is unique per Category (for which it has an FK).

So something like this:

entityTypeBuilder
  .HasIndex(i => new { i.Name, i.Category.Id })
  .IsUnique();

But this fails when I generate a migration, because of the Category.Id navigation property.

I know I can hardcode the values as strings, but I don't want to lose the static typing.

What options do I have?

Answer 1

As soon as you know the shadow property name, you can use (at least in EF Core 1.1.0) the string based HasIndex method overload

public virtual IndexBuilder HasIndex(params string[] propertyNames)

e.g.

entityTypeBuilder
  .HasIndex("Name", "CategoryId")
  .IsUnique();

Same for HasAlternateKey:

entityTypeBuilder
  .HasAlternateKey("Name", "CategoryId");

Answer 2

Add a foreign key for Category of CategoryId on the entity in question and use that in the index builder instead of the navigation property.