WP7 - Unable to databind to the same object from two pages - windows-phone-7

Question

Page1 creates and databinds to a new instance of Foo (call it theFoo)
theFoo.Name is set via textbox from Page1
theFoo is saved to a globally accessible data structure (list of Foos, whatever)
navigate from Page1 to Page2
Page2 databinds to the global list of Foos, to display all Foo instances
When I do this, I can verify that the Foo instance is added to the global list. But Page2 never shows any Foos.
If I manually add Foos to the global list (in code instead of from Page1), then navigate to Page2 without ever navigating to Page1 at all, I see Foos displayed in Page2.
What's the issue here?
Update:
Here's some relevant code...
Item.cs (Data and global storage structure)
public class Item
{
public string Name { get; set; }
}
internal static class ItemRepos
{
private static List<Item> _items = new List<Item>();
public static Item New()
{
return new Item();
}
public static int Count
{
get { return _items.Count; }
}
public static IEnumerable<Item> GetAll()
{
return _items;
}
public static Item Get( string name )
{
return _items.SingleOrDefault( item => item.Name == name );
}
public static void Save( Item item )
{
if ( _items.Contains( item ) == false )
{
_items.Add( item );
}
}
public static void Remove( Item item )
{
_items.Remove( item );
}
}
Relevant Page1.xaml fragment
<TextBlock Text="Name:"
Grid.Row="0"
Grid.Column="0"
HorizontalAlignment="Right"
VerticalAlignment="Center"
Margin="5" />
<TextBox x:Name="txtName"
Grid.Row="0"
Grid.Column="1"
HorizontalAlignment="Stretch"
VerticalAlignment="Center"
Text="{Binding Name}" />
Page1.xaml.cs
public partial class ItemDetail : PhoneApplicationPage
{
public ItemDetail()
{
InitializeComponent();
}
protected override void OnNavigatedTo( NavigationEventArgs e )
{
base.OnNavigatedTo( e );
this.DataContext = ItemRepos.New();
}
private void Nav( object sender, EventArgs e )
{
NavigationService.Navigate( new Uri( "/Page2.xaml", UriKind.RelativeOrAbsolute ) );
}
private void Save( object sender, EventArgs e )
{
ItemRepos.Save( (Item) this.DataContext );
}
}
Relevant Page2.xaml fragment
<controls:PivotItem Header="A-Z">
<ListBox x:Name="listAZ"
ItemsSource="{Binding}">
<ListBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Name}" />
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</controls:PivotItem>
Page2.xaml.cs
public partial class ViewItems : PhoneApplicationPage
{
public ViewItems()
{
InitializeComponent();
}
protected override void OnNavigatedTo( NavigationEventArgs e )
{
base.OnNavigatedTo( e );
this.DataContext = ItemRepos.GetAll();
}
}

Answer 1

Without seeing any of your code, its hard to know exactly what is going on, but I'll try guessing. If you add some code to your question, I can be more helpful. Here is a list of possible problems.
The list of Foos isn't actually static (globally accessible to both pages) and they are referencing different lists.
You Page1 isn't successfully updating the list of Foos.
If the list of Foos is an ObservableCollection, somewhere you are instatiating it more than once.
If the list of Foos isn't an ObservableCollection, you aren't setting up the data binding correctly between the two pages.
Update:
Try using the following instead of _items in Item.cs.
public static ObservableCollection<Item> Items = new ObservableCollection<Item>();
Then, change the DataContext of page 2 to use the collection directly:
protected override void OnNavigatedTo( NavigationEventArgs e )
{
base.OnNavigatedTo( e );
this.DataContext = ItemRepos.Items;
}