Entity Framework Core Create Unique Index on DateTime?

[Table("hProducaoRegistos", Schema = "Robotics")]
public class ProducaoRegisto
{
    public ProducaoRegisto()
    {
        DataCriacao = DateTime.Now;
    }

    public int Id { get; set; }
    [Display(Name = "Criado Por")]
    public int Operador { get; set; }
    [Display(Name = "Criado Em")]

    [DisplayFormat(ApplyFormatInEditMode = true, DataFormatString = "{0:dd-MM-yyyy}")]
    public DateTime DataCriacao { get; set; }                
    public int CelulaId { get; set; }
    public Celula Celula { get; set; }
    public int TurnoId { get; set; }
    public Turno Turno { get; set; }

    public virtual ICollection<CheckListRegisto> CheckListRegistos { get; set; }
    public virtual ICollection<ProcessoRegisto> ProcessoRegistos { get; set; }
    public virtual ICollection<DefeitoRegisto> DefeitoRegistos { get; set; } 
}

I want to have only a record unique by day, how can I do this using EF7? The objective is to make the user create a record only once per day until midnight of next day.