[Table("User")]
class User{
 [Key]
 public int idUser;
 public int idComputer; //ForeignKey
}

[Table("Computer")]
class Computer{
 [Key]
 public int idComputer;
}

public class User
    {
        public User()
        {
        }

        public int idUser; { get; set; }
        [Required]
        public string UserName { get; set; }


        public virtual Computer Computer{ get; set; }

    }


public class Computer
    {
        public Computer()
        {
        }
        [Key, ForeignKey("User")]
        public int idUser{ get; set; }

        public string ComputerName {get;set;}

        public virtual User User { get; set; }
    }

[Table("User")]
public class User
 {
  [Key]
  public int idUser;
  public int idComputer;
  public virtual Computer Computer;
 }

[Table("Computer")]
 public class Computer
 {

  [Key, ForeignKey("User")]
  public int idComputer;
  public virtual User User;

 }