Which side is made required by IsRequired method?

If I write:

  modelBuilder.Entity<Cart>()
            .HasOne(entity => entity.ApplicationUser)
            .WithOne(applicationUser => applicationUser.Cart)
            .IsRequired();

which property can’t be null Cart.ApplicationUser xor ApplicationUser.Cart?

>Solution :

In the code snippet you provided, both the Cart.ApplicationUser and ApplicationUser.Cart properties cannot be null. This is because the IsRequired method specifies that the relationship is required, meaning that both sides of the relationship must have a non-null value. If you only want one of the properties to be required, you can remove the IsRequired method or use a different method, such as IsOptional, to specify that the other property is allowed to be null.