Storing variables between pages VB WP8

Question

I have an app that records time as you press a button. So leave office, arrive site, leave site and arrive office. I have created a button that allows the user to input what parts have been used on the job. This takes you to another screen where input takes place. I can pass these variables back to the main page but because I'm using:

NavigationService.Navigate(New Uri("/MainPage.xaml?msg=" & textBox1.Text, UriKind.Relative))

It resets the data that was in main page.

When I use the NavigationService.GoBack(), the data remains.

Is there a way to keep that data when I am navigating away from the main page?

Answer 1

Yes, just keep the data/datacontext/object on App level.

So for example, use an object in App.xaml.vb

Public Shared Property MyBook() As Book
Get
    Return m_MyBook
End Get
Set
    m_MyBook = Value
End Set
End Property
Private Shared m_MyBook As Book

And in the OnNavigatingFrom event on your page (or even before, wherever you like), save that data

Protected Overrides Sub OnNavigatingFrom(ByVal e As System.Windows.Navigation.NavigatingCancelEventArgs)
    App.MyBook = currentBook
End Sub

When navigating back to that page, just check if the App.MyBook is null, if it's not, it means you've cached something before navigating, so just read it and set the current datacontext to it (or however you set your data on the page)

Protected Overrides Sub OnNavigatedTo(ByVal e As System.Windows.Navigation.NavigationEventArgs)
    If (App.MyBook Is Nothing) Then

    Else
        currentBook = App.MyBook
    End If
End Sub

(since you shared no relevant code, my implementation is rather abstract, but the main point is - keep it in the App.xaml.cs and save/load it when you need it)

Answer 2

Store the value in a variable at App.xaml.cs. App.xaml.cs stores variable throughout the lifetime of the app. If the value is being used frequently in other classes/pages too, then as an alternative you can either create a singleton or a static class and use it as a manager for these values. Cluttering App.Xaml.cs is not a good choice, if you have many values to store.