Better error message when using nav prop in string overload of Property

[ansydor]

I get an exception on migration adding:

System.InvalidOperationException: The property 'CreatedBy' cannot be added to the entity type 'Post' because a navigation property with the same name already exists on entity type 'Post'.

    public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
    {

        public virtual DbSet<User> DomainUsers { get; set; }
        public virtual DbSet<Post> Posts { get; set; }
        protected override void OnModelCreating(ModelBuilder builder)
        {
            base.OnModelCreating(builder);

            builder.Entity<User>(entity =>
            {
                entity.HasKey(key => key.Id);
                entity.Property(property => property.Email).IsRequired(true);
                entity.Property(property => property.Login).IsRequired(true);
                entity.Property(property => property.Created).IsRequired(true);
                entity.Property(property => property.Updated).IsRequired(true);
            });

            builder.Entity<Post>(entity =>
            {
                entity.HasKey(key => key.Id);
                entity.Property(property => property.Title).IsRequired(true);
                entity.Property(property => property.Content).IsRequired(true);
                entity.Property(property => property.Created).IsRequired(true);
                entity.Property<User>(property => property.CreatedBy).IsRequired(true);
                entity.Property(property => property.Updated).IsRequired(true);
                entity.Property<User>(property => property.UpdatedBy).IsRequired(true);
            });
        }
    }

post entity

public class Post
    {
        public int Id { get; set; }
        public string Title { get; set; }
        public string Content { get; set; }
        public DateTimeOffset Created { get; set; }
        public User CreatedBy { get; set; }
        public DateTimeOffset Updated { get; set; }       
        public User UpdatedBy { get; set; }
    }

[AndriySvyryd]

The Property method cannot be used to configure navigation properties. You would need to use the relationship API to accomplish it:

entity.HasOne(e => e.CreatedBy).WithMany().IsRequired()

We don't provide a Navigation() method to avoid creating under-configured relationships.

@rowanmiller Could you come up with an exception message that conveys this?

[zabulus]

Just encountered the same. Exception message should be changed to not confuse users.