WP7 listbox binding not working properly - windows-phone-7

Question

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?

Answer 1

Actually I see no point of having a separate class for ChronoLaps. Here is how I modified the code for MainPage.xaml.cs and everything seems to be working for me.
public partial class MainPage : PhoneApplicationPage
{
public ObservableCollection<ChronoLap> Laps { get; set; }
public double MeanTime { get; set; }
// Constructor
public MainPage()
{
InitializeComponent();
Laps = new ObservableCollection<ChronoLap>();
Laps.CollectionChanged += delegate
{
MeanTime = Laps.Sum(p => p.Time.TotalMilliseconds) / (Laps.Count * 1000);
};
DataContext = this;
Loaded += (s, e) =>
{
Laps.Add(new ChronoLap() {Time = TimeSpan.FromSeconds(1000)});
Laps.Add(new ChronoLap() {Time = TimeSpan.FromSeconds(1000)});
Laps.Add(new ChronoLap() {Time = TimeSpan.FromSeconds(1000)});
};
}
}

Answer 2

Try binding DataContext and ItemSource for listbox..
How i have done is..
<ListBox x:Name="AppList" Background="White" DataContext="{Binding DisplayItem}" SelectionChanged="AppList_SelectionChanged" Height="500" Width="auto">
<ListBox.ItemTemplate>
<DataTemplate>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
And i dont know if it will help but still i will just post the code that i am using..
ItemList.cs
using System;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.Windows.Media.Imaging;
namespace AppHouseLibrary
{
public class ItemList : IComparable
{
private string _name;
public string WidgetName
{
get
{
return _name;
}
set
{
_name = value;
}
}
public int ID
{
get;
set;
}
private BitmapImage _Icon;
public BitmapImage Icon
{
get
{
return _Icon;
}
set
{
_Icon = value;
}
}
//public string arrow { get; set; }
public BitmapImage arrow { get; set; }
public int CompareTo(ItemList other)
{
return this.WidgetName.CompareTo(other.WidgetName);
}
}
}
I have a UIManager.cs class in which am refreshing the data before i load it on the UI to the user..
using System;
using System.ComponentModel;
using System.Collections.ObjectModel;
using System.Windows.Media.Imaging;
using System.Collections.Generic;
using StirLibrary.com.mportal.data.bean;
using com.mportal.utils;
using StirLibrary.com.mportal.utils;
namespace StirLibrary.com.UI
{
public class UIManager : INotifyPropertyChanged
{
private static UIManager instance = null;
private static string TAG = "UIManager";
BitmapImage arrowImage = Utils.returnImage(ImageUtils.ARROW);
public List<ItemList> data = new List<ItemList>();
public static UIManager getInstance()
{
if (instance == null)
{
instance = new UIManager();
}
return instance;
}
private ObservableCollection<ItemList> _displayItem = new ObservableCollection<ItemList>();
public ObservableCollection<ItemList> DisplayItem
{
get
{
return _displayItem;
}
}
private UIManager()
{
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(String PropertyName)
{
if (null != PropertyChanged)
{
PropertyChanged(this, new PropertyChangedEventArgs(PropertyName));
}
}
public WidgetBean[] serviceBeanList = null;
public WidgetBean[] wheelBeanList = null;
public WidgetBean getServiceWidgetBean(int selectedIndex)
{
try
{
if (serviceBeanList != null)
{
return serviceBeanList[selectedIndex];
}
}
catch (Exception e)
{
Logger.log(TAG, e.Message);
}
return null;
}
public WidgetBean getWheelWidgetBean(int selectedIndex)
{
try
{
if (wheelBeanList != null)
{
return wheelBeanList[selectedIndex];
}
}
catch (Exception e)
{
Logger.log(TAG, e.Message);
}
return null;
}
public void DisplayCatalog(string[] ServiceDisplayName, string[] WheelDisplayName, BitmapImage[] ServiceIcons, WidgetBean[] ServiceBeanList, WidgetBean[] WheelBeanList)
{
try
{
DisplayItem.Clear();
string disp1 = string.Empty;
string name = ServiceDisplayName[0];
wheelBeanList = WheelBeanList;
serviceBeanList = ServiceBeanList;
for (int i = 0; i < ServiceDisplayName.Length; i++)
{
WidgetBean bean = serviceBeanList[i];
if (bean.isCategory())
{
DisplayItem.Add(new ItemList { WidgetName = ServiceDisplayName[i], Icon = ServiceIcons[i], arrow = arrowImage });
}
else
{
DisplayItem.Add(new ItemList { WidgetName = ServiceDisplayName[i], Icon = ServiceIcons[i] });
}
}
NotifyPropertyChanged("UI");
}
catch (Exception e)
{
Logger.log(TAG,e.Message);
}
}
public void DisplayCatalog(string[] displayName, BitmapImage[] icons, WidgetBean[] beanArray)
{
try
{
serviceBeanList = beanArray;
DisplayItem.Clear();
for (int i = 0; i < displayName.Length; i++)
{
WidgetBean bean = serviceBeanList[i];
if (bean.isCategory())
{
DisplayItem.Add(new ItemList { WidgetName = displayName[i], Icon = icons[i], arrow = arrowImage });
}
else
{
DisplayItem.Add(new ItemList { WidgetName = displayName[i], Icon = icons[i] });
}
}
NotifyPropertyChanged("UI");
}
catch (Exception e)
{
Logger.log(TAG,e.Message);
}
}
}
}