_.Entity<Contacts>().HasKey(c => new { c.ownerId, c.friendId })public class Contacts
{
[Key]
[Column(Order = 0)]
public int ownerId{ get; set; }
[Key]
[Column(Order = 1)]
public int friendId { get; set; }
..._.Entity<Contragent>()
.HasMany(e => e.Prices)
.WithRequired(e => e.Contragent)
.HasForeignKey(e => e.ContragentId);protected override void OnModelCreating(DbModelBuilder _)
{
...
}