/// <summary>
        /// Returns the contacts that have last names matching the supplied value.
        /// </summary>
        /// <param name="lastName">The last anme to search for in the database.</param>
        /// <returns>An array of <c>string</c>s that contain the matching contacts.  Each entry in the <c>Array</c> contains the contact data in the format:
        ///  "lastName,firstName,phoneNumber".</returns>
        ///  <exception cref="ArgumentException">Thrown if the supplied last name to search for is over length.</exception>
        public string[] GetEntries(string lastName)
        {
            // Validate the supplied value for lastName
            if (lastName.Length > 50)
            {
                throw new ArgumentException("Last name is longer than 50 characters", "lastName");
            }

            // List to hold the returned contacts
            List <string> entries = new List <string>();

            // Create a DataContext and scope it to the database interaction
            using (PhoneBookDatabaseDataContext dataContext = new PhoneBookDatabaseDataContext())
            {
                // Call the GetEntries stored procedure in the PhoneBook database
                var results = dataContext.GetEntries(lastName).ToList();

                // Loop over the returned contacts and populate the reulsts list, formatting each contact that was found into a single string
                foreach (PhoneBook entry in results)
                {
                    entries.Add(formatRecord(entry.LastName) + formatRecord(entry.FirstName) + entry.PhoneNumber.TrimEnd());
                }
            }

            // Return the results list as an arry of strings
            return(entries.ToArray());
        }
        /// <summary>
        /// Adds a new contact to the database.
        /// </summary>
        /// <param name="lastName">The last name of the contact.</param>
        /// <param name="firstName">The first name of the contact.</param>
        /// <param name="phoneNumber">The phone number of the contact.</param>
        /// <returns>A <c>string</c> stating "Contact added" if the contact was successfully added to the database.</returns>
        /// <exception cref="ArgumentException">Thrown if any of the supplied values is over length.</exception>
        public string AddEntry(string lastName, string firstName, string phoneNumber)
        {
            // Validate the supplied paramters
            validateContact(lastName, firstName, phoneNumber);

            // Create a DataContext and scope it to the database interaction
            using (PhoneBookDatabaseDataContext dataContext = new PhoneBookDatabaseDataContext())
            {
                // Call the AddEntry stored procedure in the database to add the contact
                dataContext.AddEntry(lastName, firstName, phoneNumber);
            }

            // Return a message stating that the contact was added successfully
            return("Contact added");
        }