Question

I am having trouble with a homework assignment, were we are supposed to make a phonebook. The condition is that it is supposed to look like this:

Class Phonebook   
{
    private List<Entry> _phoneList;
    public Phonebook()
    {
       //instance of _phoneList
    }
    public void AddEntry (string name, string number)
    {
       //logic
    }
    public string FindEntry (string namne)
    {
       //logic
    }
}

class Entry
{
  public string Name{ get; private set; }
  public string Number{ get; private set; }
}

However, I am not certain in how to make the AddEntry method assign new names/numbers to Entry list _phoneList. I have tried a lot, but to no avail. Any hints how to make it work? Any help would be much appreciated!

My code thus far looks like this

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace app3
{
    public partial class Form1 : Form
    {
        private Phonebook phonebook;
        public Form1()
        {
            InitializeComponent();
            phonebook = new Phonebook();
        }
            private void addEntryButton_Click(object sender, EventArgs e)
        {
            phonebook.AddEntry((addNameTextBox.Text), (addNumberTextBox.Text));
        } 
    } 
    class Phonebook
    {
        private List<Entry> _phoneList;
        public Phonebook()
        {  
            List<Entry> _phoneList = new List<Entry>(); 
        }
        public void AddEntry(string name, string number)
        {
        }
    }
    class Entry
    {
        public string Name { get; private set; }
        public string Number { get; private set; }
    }
}

Answer 1

Since _phoneList is a collection of Entry‘s, you need to create a new instance and add it to the list.

Entry entry = new Entry();
entry.Name = name;
entry.Number = number;
_phoneList.Add(entry);

However since Entry has private setters for the properties, you should add a new constructor taking in the name and number and set it there instead.

class Entry
{
    public Entry(string name, string number)
    {
       Name = name;
       Number = number;
    }

    public string Name { get; private set; }
    public string Number { get; private set; }
}

and then it would simply become

_phoneList.Add(new Entry(name, number));

Edit:

private List<Entry> _phoneList;
public Phonebook()
{  
  List<Entry> _phoneList = new List<Entry>(); 
}

You declare _phoneList as a private field, but then you re-declare it in your constructor which hides the original.

When you later use _phoneList in your AddEntry method, you’re getting the uninitialized field. Change the constructor to

_phoneList = new List<Entry>();