PhoneBook

The PhoneBook class provides simple management of a collection of PhoneNumber objects. The PhoneBook allows for adding and retrieving phone numbers; it supports search for phone numbers by the telephone number or by a last name.

• Constructor – Create a new List<PhoneNumber> for the numbers field.
• AddPhoneNumber(Entry : PhoneNumber) – Add a PhoneNumber to the collection. Ensure that the PhoneNumber exists (is not null) before adding; if the PhoneNumber is null, throw an exception.
• GetPhoneNumber(Index : Integer) : PhoneNumber – Get an item from a particular position in the collection.
• GetCount() : Integer – Get the size of the collection, which is a count of how many PhoneNumber objects are in the collection.
• FindPhoneNumber(TelephoneNumber : String) : PhoneNumber – Look through the collection and return a PhoneNumber with a matching telephone number. If none is found, return null.
• FindPhoneNumbersByLastName(LastName : String) : List<PhoneNumber> - Look through the collection for PhoneNumber objects with a matching last name. Add those objects to a new collection and return the collection of matching PhoneNumbers. If no items are found, return an empty collection.

Supporting Classes

The PhoneNumber class used in this sample is provided for you. The following class diagram shows the design of this class.

PhoneBook Class

public class PhoneBook
{
    private List<PhoneNumber> Number { get; set; }

    public PhoneBook()
    {
        Number = new List<PhoneNumber>();
    }

    public void AddPhoneNumber(PhoneNumber entry)
    {
        if (entry == null)
            throw new System.Exception("The phone number entry cannot be null");
        Number.Add(entry);
    }

    public PhoneNumber GetPhoneNumber(int index)
    {
        return Number[index];
    }

    public int Count
    {
        get
        {
            return Number.Count;
        }
    }

    public PhoneNumber FindPhoneNumber(string telephoneNumber)
    {
        PhoneNumber found = null;
        foreach (PhoneNumber item in Number)
        {
            if (item.Number.Equals(telephoneNumber))
            {
                found = item;
                break;
            }
        }
        return found;
    }

    public List<PhoneNumber> FindPhoneNumbersByLastName(string lastName)
    {
        List<PhoneNumber> found = new List<PhoneNumber>();
        foreach (PhoneNumber item in Number)
        {
            if (item.LastName.Equals(lastName))
            {
                found.Add(item);
            }
        }
        return found;
    }
}