Where LINQ doesn't work when filtering DateTIme, what's wrong?

Question

ASP.NET

if (dto.birthDate != "")
                {
                    DateTime birthDate = Convert.ToDateTime(dto.birthDate);
                    DateTime birthDate1 = Convert.ToDateTime(dto.birthDate).AddDays(1).AddTicks(-1);

                    items = items.Where(e => e.BirthDate >= birthDate && e.BirthDate <= birthDate1);
                }

After items is nullified