What happens to the values of object in windows phone 8 navigation? - windows-phone-8

Question

When navigating for one page to another does the value of the objects in the previous pages get lost? As I am navigating from page-1 to page-2 and then in page-2 I am calling a method which is in page-1 the values returned are null.
Why is this happening?
first page:
public Offer qw()
{
return off;
}
NavigationService.Navigate(new Uri("/Page1.xaml" ,UriKind.Relative));
page2:
var ob=obj.qw();
values in ob=null

Answer 1

if you are creating your obj field in your page2 means you are creating a new instance of the page1 so obviously it will differ from previous page.
so if you want to execute thi sfunctionality in page behind means you can do this in your page2
protected override void OnNavigatedFrom(NavigationEventArgs e)
{
// NavigationEventArgs returns destination page
Page destinationPage = e.Content as Page2;
if (destinationPage != null)
{
// Change property of destination page
destinationPage.Page1=this;
}
}

Answer 2

This is bad logic for Windows Phone application. If you need to send some object from Page_1 to Page_N you should use PhoneApplicationService, if you send some simple object-type (numbers, strings, bools) you can use NavigationContext.
Sample PhoneApplicationService:
// Page_1 before navigate to Page_N
PhoneApplicationService.Current.State[key] = value; // key(string); value(any object)
// Page_N
object o;
PhoneApplicationService.Current.State.TryGetValue(key, out o)
// then do what you want with you object - o
Sample NavigationContext:
// Page_1 before navigate to Page_N
NavigationService.Navigate(new Uri("/SecondPage.xaml?msg=SomeMessageText", UriKind.Relative));
// Page_N
protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
{
base.OnNavigatedTo(e);
string msg = "";
if (NavigationContext.QueryString.TryGetValue("msg", out msg))
string yourMessage = msg;
}
See MSDN:
NavigationContext
PhoneApplicationService and PhoneApplicationService samples