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c#entity-frameworkef-code-firstentity-framework-core

Does EF Core allow a unique column to contain multiple nulls?

My entity has a property which is allowed to be null. BUT, if it isn't null, then it must be unique. In other words, the column is unique but allows multiple nulls.

I've tried:

config.Property(p => p.ProductId).IsRequired(false);

I remember struggling to get this to work in pre-Core EF.

Is this possible? How do I configure the entity?

Solution

  • Yes, you can do that with EF Core, as a Unique index by default is created as a filtered index (WHERE ... IS NOT NULL)

    config.Entity<Product>()
        .HasIndex(b => b.ProductId)
        .IsUnique();

    https://github.com/aspnet/EntityFramework/pull/2868