Question

I am having a problem with my Listbox not updating/refresing.I have read here that i need to use ObservableCollection but i didn’t have any luck.I am populating my Listbox from a XML.

 public class PestotoraPost
    {
        public string ID { get; set; }
        public string Date { get; set; }
        public string Name { get; set; }
        public string Message { get; set; }

    }
void WebLoad()
    {
        WebClient pestotora = new WebClient();
        pestotora.DownloadStringCompleted += new DownloadStringCompletedEventHandler(pestotora_DownloadStringCompleted);
        pestotora.DownloadStringAsync(new Uri("wwww.someURL.com/xml.php"));

    }

Note that the actual xml is a php containing the xml structure (from a sql DB)

 void pestotora_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
    {
        XElement doc = XElement.Parse(e.Result);
        listBox1.ItemsSource = from results in doc.Descendants("Data")
                            select new PestotoraPost
                            {
                                ID = results.Element("DataID").Value,
                                Date = results.Element("DataDate").Value,
                                Name=results.Element("DataName").Value,
                                Message=results.Element("DataMessage").Value     
                            };
    }

Everytime the XML changes,my Listbox won’t update doing a listBox1.UpdateLayout();

Any clue/help on how to start implementing this one?
Thank you very much.

UPDATED

namespace pestotora
{
    public partial class MainPage : PhoneApplicationPage
    {
        // Constructor
        public MainPage()
        {
            InitializeComponent();
            UIload(true);
            WebLoad();

        }

        public ObservableCollection<PestotoraPost> Posts { get; set; }

        public class PestotoraPost
        {
            public string ID { get; set; }
            public string Date { get; set; }
            public string Name { get; set; }
            public string Message { get; set; }
        }


        void WebLoad()
        {

            WebClient pestotora = new WebClient();
            pestotora.DownloadStringCompleted += new DownloadStringCompletedEventHandler(pestotora_DownloadStringCompleted);
            pestotora.DownloadStringAsync(new Uri("www.domain.com/xml.php"));

        }

        void UIload(bool Splash)
        {
            if (Splash == true)
            {

                ApplicationBar.IsVisible = false;
            }
            else
            {

                ApplicationBar.IsVisible = true;
            }
        }

        void pestotora_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
        {
            //XDocument doc = XDocument.Parse(e.Result);

            XElement doc = XElement.Parse(e.Result);


            /* listBox1.ItemsSource = from results in doc.Descendants("Data")
                                select new PestotoraPost
                                {
                                    ID = results.Element("DataID").Value,
                                    Date = results.Element("DataDate").Value,
                                    Name=results.Element("DataName").Value,
                                    Message=results.Element("DataMessage").Value

                                }; */
            var list = from results in doc.Descendants("Data")
                       select new PestotoraPost
                       {
                           ID = results.Element("DataID").Value,
                           Date = results.Element("DataDate").Value,
                           Name = results.Element("DataName").Value,
                           Message = results.Element("DataMessage").Value
                       };
            Posts = new ObservableCollection<PestotoraPost>(list);
            foreach (var post in list)
            {
                Posts.Add(post);
            }

            UIload(false);


        }


        private void ApplicationBarMenuItem_Click(object sender, EventArgs e)
        {
            //stckPost.Visibility = System.Windows.Visibility.Visible;

        }



        private void ApplicationBarIconButton_Click(object sender, EventArgs e)
        {
            NavigationService.Navigate(new Uri("/Post.xaml", UriKind.Relative));
        }

        private void ApplicationBarIconButton_Click_1(object sender, EventArgs e)
        {

            listBox1.UpdateLayout();
            //listBox1.ScrollIntoView(listBox1.Items[0]);

            WebLoad();
        }

    }

}

Answer 1

1. If you use MVVM pattern: In viewModel implement INotifyPropertyChanged and declare:

private ObservableCollection<PestotoraPost> _posts;
public ObservableCollection<PestotoraPost> Posts 
{
 get{return _posts;} 
 set
  {
     _posts = value;
     RaisePropertyChanged("Posts");
  }
 }

in xaml write:

<ListBox Name="listbox1" ItemsSource="{Binding Posts}"/>

in pestotora_DownloadStringCompleted method:

var list = from results in doc.Descendants("Data")
                            select new PestotoraPost
                            {
                                ID = results.Element("DataID").Value,
                                Date = results.Element("DataDate").Value,
                                Name=results.Element("DataName").Value,
                                Message=results.Element("DataMessage").Value     
                            };
Posts = new ObservableCollection<PestotoraPosts>(list);

---

2. If you run everything in a code-behind just declare

 public ObservableCollection<PestotoraPosts> Posts {get;set;}

And in Page constructor init collection:

 Posts = new ObservableCollection<PestotoraPosts>();

Xaml will have the same declaration.
And in pestotora_DownloadStringCompleted method:

var list = from results in doc.Descendants("Data")
                            select new PestotoraPost
                            {
                                ID = results.Element("DataID").Value,
                                Date = results.Element("DataDate").Value,
                                Name=results.Element("DataName").Value,
                                Message=results.Element("DataMessage").Value     
                            };
foreach(var post in list)
{
   Posts.Add(post);
}

What have we done?

In xaml we set a databinding . Now listBox1 will get data from Post collection.
Then we created new collection and notyfied listBox1 to update it’s view. (in first vatiant).

In second variant we populated collection and as it was observable it notifyed a list box.