Question

I have small problem with retrieving the state of a canvas’ visibility property. When I retrieve the page state, the canvas is always visible even if it was collapsed when it was tombstoned. I tried a bunch of if else and switch statements but with no luck. How do I fix this bug? Thanks in advance to anyone who wants to help!

Here’s the code:

    private const string coachPivotKey = "CoachPivotKey";
    private const string isVisibleKey = "IsVisibleKey";

    protected override void OnNavigatedFrom(System.Windows.Navigation.NavigationEventArgs e)
    {
        this.SaveState(coachPivotKey, coachPivot.SelectedIndex);
        this.SaveState(isVisibleKey, canvasNotes.Visibility);
    }

    protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
    {
        coachPivot.SelectedItem = coachPivot.Items[this.LoadState<int>(coachPivotKey)];
        canvasNotes.Visibility = this.LoadState<Visibility>(isVisibleKey);

        base.OnNavigatedTo(e);
    }

The LoadState() and SaveState() methods are in a different class. These I got from a video I watched on tombstoning:

public static void SaveState(this PhoneApplicationPage phoneApplicationPage, string key, object value)
    {
        if (phoneApplicationPage.State.ContainsKey(key))
        {
            phoneApplicationPage.State.Remove(key);
        }

        phoneApplicationPage.State.Add(key, value);
    }

public static T LoadState<T>(this PhoneApplicationPage phoneApplicationPage, string key)
    {
        if (phoneApplicationPage.State.ContainsKey(key))
        {
            return (T)phoneApplicationPage.State[key];
        }

        return default(T);
    }

Answer 1

Instead of saving a System.Windows.Visibility, save a bool indicating whether the control is visible.

this.SaveState(isVisibleKey,coachNotes.Visibility == Visibility.Visible); 


canvasNotes.Visibility = this.LoadState<bool>(isVisibleKey) ? Visibility.Visible : Visibility.Collapsed;