Unable to determine the principal end of an association between the types Error

Error disebabkan adanya relasi one-to-one antar 2 tabel. Contoh skema:

Solusinya, tambahkan line berikut

[code language=”csharp”]
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Membership>().HasRequired(a => a.User).WithRequiredPrincipal(b => b.Membership);
}
[/code]

http://stackoverflow.com/questions/21849523/unable-to-determine-the-principal-end-of-an-association-between-the-types-error