WP7 listbox binding not working properly
- by Marco
A noob error for sure (I started yesterday afternoon developing in WP7), but I'm wasting a lot time on it.
I post my class and a little part of my code:
public class ChronoLaps : INotifyPropertyChanged
{
private ObservableCollection<ChronoLap> 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<ChronoLap> Laps {
get { return laps; }
set
{
if (value == laps) return;
laps = value;
if (laps != null)
{
laps.CollectionChanged += delegate
{
MeanTime = Laps.Sum(p => p.Time.TotalMilliseconds) / (Laps.Count * 1000);
NotifyPropertyChanged("MeanTime");
};
}
NotifyPropertyChanged("Laps");
}
}
}
MainPage.xaml.cs
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;
}
}
MainPage.xaml
<phone:PhoneApplicationPage>
<Grid x:Name="LayoutRoot" Background="Transparent">
<Grid Grid.Row="2">
<ScrollViewer Margin="-5,13,3,36" Height="758">
<ListBox Name="lbHistory" ItemContainerStyle="{StaticResource ListBoxStyle}"
ItemsSource="{Binding Laps}"
HorizontalAlignment="Left" Margin="5,25,0,0"
VerticalAlignment="Top" Width="444">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Lap}" Width="40" />
<TextBlock Text="{Binding Time}" Width="140" />
<TextBlock Text="{Binding TotalTime}" Width="140" />
<TextBlock Text="{Binding Distance}" />
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</ScrollViewer>
</Grid>
</Grid>
</phone:PhoneApplicationPage>
Problem is that when I add one or more items to History.Laps collection, my listbox is not refreshed and these items don't appear.
But if I remove comment on // History.Laps.Add(new ChronoLap()... line, this item appear and so every other inserted later.
More: if I remove that comment and then write History.Laps.Clear() (before or after setting binding) binding is not working anymore. It's like it gets crazy if collection is empty.
I really don't understand the reason...
UPDATE AND SOLUTION:
If i move
History = new ChronoLaps();
LayoutRoot.DataContext = History;
from butStart_Click to public MainPage() everything works as expected.
Can someone explain me the reason?
