List vs ObservableCollection vs INotifyPropertyChanged in Silverlight

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.Collections.ObjectModel;
using System.Threading;
using Microsoft.Windows.Controls.DataVisualization.Charting;
using System.ComponentModel;

namespace SLListVsObservableCollection
{
    public partial class Page : UserControl
    {
        List<UserList> usersList;
        ObservableCollection<UserOC> usersOC;
        List<UserNPC> usersNPC;
        Timer timerList;
        Timer timerOC;
        Timer timerNPC;

        public Page()
        {
            InitializeComponent();
            usersList = getUserCollectionList();
            usersOC = getUserCollectionOC();
            usersNPC = getUserCollectionNPC();

            this.dgList.ItemsSource = usersList;
            this.dgOC.ItemsSource = usersOC;
            this.dgNPC.ItemsSource = usersNPC;

            ((DynamicSingleSeriesWithAxes)this.cList.Series[0]).ItemsSource = usersList;
            ((DynamicSingleSeriesWithAxes)this.cOC.Series[0]).ItemsSource = usersOC;
            ((DynamicSingleSeriesWithAxes)this.cNPC.Series[0]).ItemsSource = usersNPC;

            timerList = new Timer(timerFiredList, null, 5000, 1000);
            timerOC = new Timer(timerFiredOC, null, 5000, 1000);
            timerNPC = new Timer(timerFiredNPC, null, 5000, 1000);

        }

        void timerFiredList(object state)
        {
            this.Dispatcher.BeginInvoke(delegate()
            {
                Random rnd = new Random();
                usersList[rnd.Next(0, usersList.Count)].Grade = rnd.Next(1, 5);

                if (rnd.Next(1, 5) > 3)
                {
                    if (usersList.Count > 4)
                    {
                        usersList.RemoveAt(4);
                    }
                    else
                    {
                        usersList.Add(new UserList { Name = "E", Grade = 1 });
                    }
                }
            });
        }
        void timerFiredOC(object state)
        {
            this.Dispatcher.BeginInvoke(delegate()
            {
                Random rnd = new Random();
                usersOC[rnd.Next(0, usersOC.Count)].Grade = rnd.Next(1, 5);

                if (rnd.Next(1, 5) > 3)
                {
                    if (usersOC.Count > 4)
                    {
                        usersOC.RemoveAt(4);
                    }
                    else
                    {
                        usersOC.Add(new UserOC { Name = "E", Grade = 1 });
                    }
                }
            });
        }
        void timerFiredNPC(object state)
        {
            this.Dispatcher.BeginInvoke(delegate()
            {
                Random rnd = new Random();
                usersNPC[rnd.Next(0, usersNPC.Count)].Grade = rnd.Next(1, 5);

                if (rnd.Next(1, 5) > 3)
                {
                    if (usersNPC.Count > 4)
                    {
                        usersNPC.RemoveAt(4);
                    }
                    else
                    {
                        usersNPC.Add(new UserNPC { Name = "E", Grade = 1 });
                    }
                }
            });
        }

        List<UserList> getUserCollectionList()
        {
            List<UserList> rVal = new List<UserList>();

            rVal.Add(new UserList { Name = "A", Grade = 2 });
            rVal.Add(new UserList { Name = "B", Grade = 3 });
            rVal.Add(new UserList { Name = "C", Grade = 4 });
            rVal.Add(new UserList { Name = "D", Grade = 5 });
            rVal.Add(new UserList { Name = "E", Grade = 1 });

            return rVal;
        }
        ObservableCollection<UserOC> getUserCollectionOC()
        {
            ObservableCollection<UserOC> rVal = new ObservableCollection<UserOC>();

            rVal.Add(new UserOC { Name = "A", Grade = 2 });
            rVal.Add(new UserOC { Name = "B", Grade = 3 });
            rVal.Add(new UserOC { Name = "C", Grade = 4 });
            rVal.Add(new UserOC { Name = "D", Grade = 5 });
            rVal.Add(new UserOC { Name = "E", Grade = 1 });

            return rVal;
        }
        List<UserNPC> getUserCollectionNPC()
        {
            List<UserNPC> rVal = new List<UserNPC>();

            rVal.Add(new UserNPC { Name = "A", Grade = 2 });
            rVal.Add(new UserNPC { Name = "B", Grade = 3 });
            rVal.Add(new UserNPC { Name = "C", Grade = 4 });
            rVal.Add(new UserNPC { Name = "D", Grade = 5 });
            rVal.Add(new UserNPC { Name = "E", Grade = 1 });

            return rVal;
        }
    }

    public class UserList
    {
        public string Name { get; set; }
        public int Grade { get; set; }
    }
    public class UserOC
    {
        public string Name { get; set; }
        public int Grade { get; set; }
    }

    public class UserNPC:INotifyPropertyChanged
    {
        private string name;
        public string Name { 
            get { return name; } 
            set { name = value; onPropertyChanged(this, "Name"); } 
        }

        public int grade;
        public int Grade { 
            get { return grade; } 
            set { grade = value; onPropertyChanged(this, "Grade"); } 
        }

        #region INotifyPropertyChanged Members
        // Declare the PropertyChanged event
        public event PropertyChangedEventHandler PropertyChanged;

        // OnPropertyChanged will raise the PropertyChanged event passing the
        // source property that is being updated.
        private void onPropertyChanged(object sender, string propertyName)
        {

            if (this.PropertyChanged != null)
            {
                PropertyChanged(sender, new PropertyChangedEventArgs(propertyName));
            }
        }

        #endregion
    }
}