program blows up on navigate using observable collections WP7 - data-binding

Question

In maine, on my button click event handler I do:
private void addIconButton_Click(object sender, EventArgs e)
{
if (test)
{
MessageBox.Show("enters addIcon Main");
Note note = new Note();
note.Modified = DateTimeOffset.Now;
if (note != null)
{
Settings.NotesList.Add(note); //this causes the issue.
//Settings.NotesList[0] = note;
}
Settings.CurrentNoteIndex = 0;
test = false;
MessageBox.Show("right before navigate");
this.NavigationService.Navigate(new Uri("/DetailsPage.XAML", UriKind.Relative));
MessageBox.Show("after navigate");
}
//DetailsPage mynewPage = new DetailsPage();
//this.Content = mynewPage;
}
and on my on navigatedTo I do:
protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
{
MessageBox.Show("enters onNav Main");
DataContext = null;
DataContext = Settings.NotesList;
Settings.CurrentNoteIndex = -1;
Listbox.SelectedIndex = -1;
if (Settings.NotesList != null)
{
if (Settings.NotesList.Count == 0)
{
Notes.Text = "No Notes";
}
else
{
Notes.Text = "";
}
}
}
Inside my front end code I do:
<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
<ListBox x:Name="Listbox" SelectionChanged="listbox_SelectionChanged" ItemsSource="{Binding}">
<ListBox.ItemTemplate>
<DataTemplate>
<Border Width="800" MinHeight="60">
<StackPanel>
<TextBlock x:Name="Title" VerticalAlignment="Center" FontSize="{Binding TextSize}" Text="{Binding Name}"/>
<TextBlock x:Name="Date" VerticalAlignment="Center" FontSize="{Binding TextSize}" Text="{Binding Modified,
Mode=TwoWay, Converter={StaticResource dateConverter}}"/>
</StackPanel>
</Border>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</Grid>
</Grid>
I have an observable collections in a static class where in the constructor I set it to:
public static class Settings
{
public static ObservableCollection<Note> NotesList;
static IsolatedStorageSettings settings;
private static int currentNoteIndex;
static Settings()
{
NotesList = new ObservableCollection<Note>();
settings = IsolatedStorageSettings.ApplicationSettings;
MessageBox.Show("enters constructor settings");
}
and then inside the Notes class it just looks like this:
public class Note
{
public DateTimeOffset Modified { get; set; }
public string Title { get; set; }
public string Content { get; set; }
public int TextSize { get; set; }
}
when I click the app button and it calls the invent handler right after the navigationService is called I get:
// Code to execute on Unhandled Exceptions
private void Application_UnhandledException(object sender, ApplicationUnhandledExceptionEventArgs e)
{
if (System.Diagnostics.Debugger.IsAttached)
{
// An unhandled exception has occurred; break into the debugger
System.Diagnostics.Debugger.Break();
}
}
this only happens when Settings.NotesList.Add(note); is added in the addIconButton_click method..
Any suggestions???

Answer 1

I fixed it by setting default values to the instance variables in the Notes class inside the constructor...