Loading Names

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 Microsoft.Phone.Controls;
using System.IO.IsolatedStorage;
using System.Xml.Serialization;
using System.IO;
using System.Xml.Linq;

namespace LasnaoloAppsi
{
    public partial class LasnaoloLista : PhoneApplicationPage
    {
        string id = string.Empty;
        XDocument lista = XDocument.Load("NykyisetKurssit.xml");

        public LasnaoloLista()
        {
            InitializeComponent();
        }

        protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
        {
            const string id1 = "504T11";
            const string id2 = "504T12";
            const string id3 = "504T10";
            const string id4 = "504T09";

            string r504T11 = "People.xml";
            string r504T12 = "People2.xml";
            string r504T10 = "People3.xml";
            string r504T09 = "People4.xml";

            if (NavigationContext.QueryString.TryGetValue("id", out id))
            {
                var ryhma = (from ryhmaInfo in lista.Descendants("Kurssi")
                             where ryhmaInfo.Attribute("id").Value == id
                             select new Kurssit
                             {
                                 RyhmanNimi = (string)ryhmaInfo.Element("tunnus").Value

                             }).FirstOrDefault();

                PageTitle.Text = ryhma.RyhmanNimi;

                switch (id)
                {
                    case id1:

                        LoadLasnaolot(r504T11);
                        break;

                    case id2:

                        LoadLasnaolot(r504T12);
                        break;

                    case id3:
                        LoadLasnaolot(r504T10);
                        break;

                    case id4:
                        LoadLasnaolot(r504T09);
                        break;
                }
            }


            base.OnNavigatedTo(e);
        }

        public void LoadLasnaolot(string filename)
        {
            try
            {
                using (IsolatedStorageFile ISF = IsolatedStorageFile.GetUserStoreForApplication())
                {
                    using (IsolatedStorageFileStream str = ISF.OpenFile(filename, FileMode.Open))
                    {
                        XmlSerializer serializer = new XmlSerializer(typeof(List<Kurssit>));
                        List<Kurssit> l1 = (List<Kurssit>)serializer.Deserialize(str);
                        this.LasnaoloListax.ItemsSource = l1;
                    }
                }
            }
            catch
            {
                //add some code here
            }

        }
    }
}