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POWP7 listbox binding not working properly
 

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    <p>A noob error for sure (I started yesterday afternoon developing in WP7), but I'm wasting a lot time on it.<br> I post my class and a little part of my code:</p> <pre><code>public class ChronoLaps : INotifyPropertyChanged { private ObservableCollection&lt;ChronoLap&gt; laps = null; public int CurrentLap { get { return lap; } set { if (value == lap) return; // Some code here .... ChronoLap newlap = new ChronoLap() { // Some code here ... }; Laps.Insert(0, newlap); lap = value; NotifyPropertyChanged("CurrentLap"); NotifyPropertyChanged("Laps"); } } public ObservableCollection&lt;ChronoLap&gt; Laps { get { return laps; } set { if (value == laps) return; laps = value; if (laps != null) { laps.CollectionChanged += delegate { MeanTime = Laps.Sum(p =&gt; p.Time.TotalMilliseconds) / (Laps.Count * 1000); NotifyPropertyChanged("MeanTime"); }; } NotifyPropertyChanged("Laps"); } } } </code></pre> <p><strong>MainPage.xaml.cs</strong></p> <pre><code>public partial class MainPage : PhoneApplicationPage { public ChronoLaps History { get; private set; } private void butStart_Click(object sender, EventArgs e) { History = new ChronoLaps(); // History.Laps.Add(new ChronoLap() { Distance = 0 }); LayoutRoot.DataContext = History; } } </code></pre> <p><strong>MainPage.xaml</strong></p> <pre><code>&lt;phone:PhoneApplicationPage&gt; &lt;Grid x:Name="LayoutRoot" Background="Transparent"&gt; &lt;Grid Grid.Row="2"&gt; &lt;ScrollViewer Margin="-5,13,3,36" Height="758"&gt; &lt;ListBox Name="lbHistory" ItemContainerStyle="{StaticResource ListBoxStyle}" ItemsSource="{Binding Laps}" HorizontalAlignment="Left" Margin="5,25,0,0" VerticalAlignment="Top" Width="444"&gt; &lt;ListBox.ItemTemplate&gt; &lt;DataTemplate&gt; &lt;StackPanel Orientation="Horizontal"&gt; &lt;TextBlock Text="{Binding Lap}" Width="40" /&gt; &lt;TextBlock Text="{Binding Time}" Width="140" /&gt; &lt;TextBlock Text="{Binding TotalTime}" Width="140" /&gt; &lt;TextBlock Text="{Binding Distance}" /&gt; &lt;/StackPanel&gt; &lt;/DataTemplate&gt; &lt;/ListBox.ItemTemplate&gt; &lt;/ListBox&gt; &lt;/ScrollViewer&gt; &lt;/Grid&gt; &lt;/Grid&gt; &lt;/phone:PhoneApplicationPage&gt; </code></pre> <p>Problem is that when I add one or more items to <code>History.Laps</code> collection, my listbox is not refreshed and these items don't appear.<br> But if I remove comment on <code>// History.Laps.Add(new ChronoLap()...</code> line, this item appear and so every other inserted later.<br> More: if I remove that comment and then write <code>History.Laps.Clear()</code> (before or after setting binding) binding is not working anymore. It's like it gets crazy if collection is empty.<br> I really don't understand the reason...</p> <p><strong>UPDATE AND SOLUTION</strong>:<br> If i move</p> <pre><code>History = new ChronoLaps(); LayoutRoot.DataContext = History; </code></pre> <p>from <code>butStart_Click</code> to <code>public MainPage()</code> everything works as expected.<br> Can someone explain me the reason?</p>
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    1. COCan't see anything obvious. Where are you actually setting the value of laps?
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    2. COwhere are you adding the Laps to History? when adding the Laps, remove the control’s binding before updating the list, and re-apply them afterwards and see
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    3. CO@Stuart: I'm adding Laps inside my class as showed in my modified question. Remove and re-apply binding? It could be a way, but which is the reason? Thanks
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