Question

I have an application for Windows 8 with a page (Frame) for displaying a list of items and a page for downloading & displaying the items details. I am also using MVVM Light for sending notifications.

Application use goes something like this:

1. Open Main Page

2. Navigate to List Page

   Frame.Navigate(typeof(MyPage));
   

3. Choose Item

   //Complete logic
   Frame.GoBack();
   

4. Back on Main Page, I start downloading the file in the view model, I send ONE NotificationMessage saying BeginDownloadFile and after it is downloaded ONE NotificationMessage saying EndDownloadFile.

The first time I do steps 2,3, & 4 my NotificationReceived method is hit once, the second twice and so forth.

private async void NotificationMessageReceived(NotificationMessage msg)
{
    if (msg.Notification == Notifications.BeginDownloadFile)
    {
       FileDownloadPopup.IsOpen = true;
    }
    else if (msg.Notification == Notifications.EndDownloadFile)
    {
       FileDownloadPopup.IsOpen = false;
    }
}

Additional information: I only have one FileDownloadPopup, yet each time, an additional popup is shown each time the NotificationMessageReceived method is called.

My only conclusion is that between navigating forwards and backwards in my app, there are multiple MainPages being created and never closed. This results in many NotificationsMessageReceived methods just waiting for a notification to come their way so they can show their popup.

I have two questions:
1. Does this sound like normal behaviour for a Windows 8 app?
2. How can I close all instances of the MainPage or return to the previous instance without creating a new instance?

Please let me know if I have missed something important out before marking my question down.

Answer 1

This sounds normal to me. The default navigation behaviour in Windows 8 is to create a new page instance each time you navigate to a new page, regardless of whether this is forward or back navigation.

Try setting the NavigatinCacheMode on MainPage to Required. See the MSDN documentation for details of how page caching works.