Untitled

namespace Homework
{
    public class Person
    {
        public string FirstName
        {
            get { return FirstName; }

            set
            {
                bool isLatin = FirstName.All(c => (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z'));

                if (FirstName.Length < 1 || FirstName.Length > 30 || !isLatin)
                {
                    throw new Exception("Name is invalid");
                }
                else
                    FirstName = value;
            }
        }
        public string LastName
        {
            get { return LastName; }

            set
            {
                bool isLatin = LastName.All(c => (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z'));

                if (LastName.Length < 1 || LastName.Length > 30 || !isLatin)
                {
                    throw new Exception("Name is invalid");
                }
                else
                    LastName = value;
            }
        }
        public DateTime DateOfBirth
        {
            get { return DateOfBirth; }

            set
            {
                if (DateOfBirth.Date < DateTime.Today)
                {
                    throw new Exception("Invalid Date of Birth.");
                }
                else
                    DateOfBirth = value;
            }
        }
        public string ID
        {
            get { return ID; }

            set
            {
                int digits = 0;

                for (int i = 2; i < ID.Length; i++)
                {
                    if (Char.IsDigit(ID[i]))
                    {
                        digits++;
                    }
                }
                if (!Char.IsUpper(ID[0]) || !Char.IsUpper(ID[1]) || digits != 10)
                {
                    throw new Exception("Invalid ID number");
                }
                ID = value;
            }
        }
        public Person(string firstName, string lastName, DateTime dateOfBirth, string iD)
        {
            FirstName = firstName;
            LastName = lastName;
            DateOfBirth = dateOfBirth;
            ID = iD;
        }
    }
public interface IPersonRepository
    {
        Person GetByFirstName(string firstName);
        Person GetByLastName(string lastName);
        Person GetById(string id);
        void Add(Person person);

    }
public class PersonRepository : IPersonRepository
    {

        public List<Person> People;

        public PersonRepository(List<Person> people)
        {
            this.People = people;
        }

        public Person GetByFirstName(string firstName)
        {
            foreach (Person person in People)
            {
                if (person.FirstName == firstName)
                {
                    return person;
                }
            }
            return null;
        }

        public Person GetByLastName(string lastName)
        {
            foreach (Person person in People)
            {
                if (person.LastName == lastName)
                {
                    return person;
                }
            }
            return null;
        }

        public Person GetById(string id)
        {
            foreach (Person person in People)
            {
                if (person.ID == id)
                {
                    return person;
                }
            }
            return null;
        }

        public void Add(Person person)
        {
            if (GetByFirstName(person.FirstName) == null || GetByLastName(person.LastName) == null || GetById(person.ID) == null)
            {
                People.Add(person);
            }
        }
    }
}