Could not find an implementation of the query pattern for source type 'DbSet'. 'Select' not found

Question

I have a dbcontext with a dbset, and I need to make a linq query easily.

using (ZigBeeContext db = new ZigBeeContext())
                {
                    var lista = (from p in db.Medidas
                                 select new Medida
                                 {
                                     Fecha = p.FechaHora,

                                 }).ToList();
                }

However I get the error on the title on db.Medidas

Medidas.cs

 public class Medida
    {
        [Key]
        [DisplayName("Medida")]
        public int MedidaID { get; set; }

        public decimal Temperatura { get; set; }
        public int Humedad { get; set; }

        public DateTime FechaHora { get; set; }

        [DisplayName("Dispositivo")]        
        public int DispositivoID { get; set; }
        public virtual Dispositivo Dispositivo { get; set; }



    }