Silverlight/XNA Data Binding Irregularity

Question

I have to preface this with a disclaimer. I'm a novice programmer, I've tried solving this on my own for days but have now completely run out of ideas/blog posts/walkthroughs and other sources. I really appreciate your time in reading and potentially replying.

I am trying to integrate scoreloop into a game I'm developing but am getting some very strange results with data binding and a listbox. My tests (below) imply that there has to be something I'm doing wrong with bindings, but the crazy thing is it actually works the first time I use it, but not for subsequent levels. Here is the important code I'm using:

XAML:

<ListBox x:Name="LeftListBox" Margin="12,48,0,128" ItemsSource="{Binding}" Background="{x:Null}" HorizontalAlignment="Left" Width="240">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <StackPanel Margin="0,0,0,17">
                        <StackPanel Margin="0,0,0,0" Orientation="Horizontal" HorizontalAlignment="Left">
                            <TextBlock Text="{Binding Rank}" TextWrapping="NoWrap"  />
                            <TextBlock Text="." Width="54"/>
                            <TextBlock Text="{Binding Result}" TextWrapping="NoWrap" Width="76"/>
                            <TextBlock Text="{Binding User.Login}" TextWrapping="NoWrap"/>
                        </StackPanel>                           
                    </StackPanel>
                </DataTemplate>
            </ListBox.ItemTemplate>             
        </ListBox>

I have an event registered to fire whenever scores are loaded, this sets the binding and logs a debug message:

LeftListBox.DataContext = App._scoresController.Scores;
Debug.WriteLine("Scores Loaded");  

App._scoresController.Scores contains User.Login, Rank, and Result.

After I beat a level it pulls down scores and displays them int he listbox just like I expect. As soon as it goes through the same cycle for the next level though the listbox is blank. The debug line of "Scores Loaded" always gets logged, so I know the event is firing.

What I've done so far in testing:

1. Turned on ALL for bindings logging and could not see anything getting logged in the output.
2. Set a break point at the Debug "Scores Loaded" line and can see that everytime it hits there it correctly assigned the datacontext, with the correct fields with exactly matching names
3. Tried using Dispatcher.BeginInvoke(LoadScores); to be sure I was doing it off the UI thread in case this was somehow a threading issue
4. Set the background color on the stackpanel to a color that I could use to ensure it wasn't being collapsed or hidden by another control or a storyboard animation
5. Created a copy of the same listbox, set listbox.datacontext = this in the same LoadScores() method, then set up local variables for it to bind to. Found that this exhibited the same behavior, disappearing on the second time I go to set the datacontext
6. Created a copy of the listbox and removed all bindings, setting the three text fields manually. This would not disappear, but showed up every time I beat a level
7. Beat one level (getting it to work), beat another (getting it to disappear), navigate away from the gamepage.xaml/gamepage.xaml.cs where the gameplay takes place (like to a mainpage.xaml, then back to the gamepage. This does not fix the problem, so I'm assuming the problem is higher up than something inside the gamepage.xaml/gamepage.xaml.cs

I feel like I've got to be doing something painfully stupid/obvious, but I'm a novice programmer, just picking pieces up as I have a need, and this is my first venture into the world of data binding. I would greatly appreciate any suggestions.

Thanks in advance for your time.

Answer 1

I found the problem. I was wrong when I said I was never leaving the GamePage.xaml.cs and Gamepage.xaml.

I reveiwed my code and found that I was actually jumping out to a transition page that lists the details of the next level, then back to GamePage.

Whenever I left the page, strange things would happen to the App._scoresController.Scores. If I created a private _scoresController.Scores within GamePage.xaml.cs and used that instead of the one in App then everything works. It looks like something strange with Scoreloop.