Windows Phone Navigation code error - silverlight

Question

where am I going wrong here?
private void lstCars_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
string currCar = (sender as ListBox).SelectedItem as string;
NavigationService.Navigate(new Uri("/ViewCarDetails.xaml?info=" + currCar, UriKind.Relative));
}
here is the page im trying to navigate to
public ViewCarDetails(string registrationNum)
{
//stuff
}
and here is the code that the program jumps to when I get an error (in App.xaml.cs)
private void RootFrame_NavigationFailed(object sender, NavigationFailedEventArgs e)
{
if (System.Diagnostics.Debugger.IsAttached)
{
// A navigation has failed; break into the debugger
System.Diagnostics.Debugger.Break();
}
}
ive checked the URI but no typos
Thank you

Answer 1

The problem is that your are passing a parameter via NavigationService and ViewCarDetails class constructor is expecting a parameter that you are not passing through.
To solve it you have to create a constructor with no parameters and take the parameter you are passing through navigationservice from NavigatedTo event as follow:
public ViewCarDetails()
{
//stuff
}
and
protected override void OnNavigatedTo(NavigationEventArgs e)
{
string registrationNum = string.Empty;
if (NavigationContext.QueryString.TryGetValue("index", out registrationNum))
{
//do stuff
}
}
Try it out and let us know,
ADDED:
public class ViewCarDetails : PhoneApplicationPage
{
private string registrationNum;
public ViewCarDetails()
{
//stuff
}
protected override void OnNavigatedTo(NavigationEventArgs e)
{
registrationNum = string.Empty;
if (NavigationContext.QueryString.TryGetValue("index", out registrationNum))
{
//do stuff
}
}
//other methods and properties
}
regards,