Entity Framework error while saving changes - entity-framework

Question

I'm new to Entity Framework. At the moment I'm having a problem - when I try to insert a new User object into the database (using method RegisterNewUser), I keep getting an error:
Violation of PRIMARY KEY constraint 'PK__Users__3214EC07705D23AE'. Cannot insert duplicate key in object 'dbo.Users'. The duplicate key value is (0).
There are some similar questions here, but none of these answers have helped me.
public void RegisterNewUser(String uName, String uPass, String fName, String lName, String email)
{
User user = new User();
user.Username = uName;
user.Password = uPass;
user.FirstName = fName;
user.LastName = lName;
user.Email = email;
Time time = new Time();
time.Time1 = DateTime.Now;
user.Times.Add(time);
ur.AddUser(user);
}
Time and User objects:
public partial class Time
{
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
public int UserId { get; set; }
public System.DateTime Time1 { get; set; }
public virtual User User { get; set; }
}
public partial class User
{
public User()
{
this.Times = new HashSet<Time>();
}
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
public string Username { get; set; }
public string Password { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string Email { get; set; }
public virtual ICollection<Time> Times { get; set; }
}
Repository file
public class UsersRepository
{
UsersDBContext userDBContext = new UsersDBContext();
public List<User> GetUsers()
{
return userDBContext.Users.Include("Times").ToList();
}
public void AddUser(User user)
{
userDBContext.Users.Add(user);
userDBContext.SaveChanges();
}
}
And context
public partial class UsersDBContext : DbContext
{
public UsersDBContext() : base("name=UsersDBContext")
{
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
throw new UnintentionalCodeFirstException();
}
public virtual DbSet<Time> Times { get; set; }
public virtual DbSet<User> Users { get; set; }
}
I have no idea how to solve this so any suggestions would be very helpful

Answer 1

set a value of Id field
or
define the Id field as autoincrement