Right now OnNavigat* methods are provided by corresponding interfaces. This means NavigationService can await asynchronous versions of these methods (and actually is doing that at this point). That soultion has some pros and cons.
Example No.1:
Client wants to start downloading something after navigating to some page. What is the natural way to do that? Well isn't that just:
public Task OnNavigatedToAsync(OnNavigatedToEventArgs e)
{
await DownloadStuff();
ChangeSomeUiStuff();
}
The problem with that is NavigationService is awaiting that, and the navigation process is not getting finished before DownloadStuff() finishes. Obviously the navigation should have ended by that time.
Of course this can be fixed by implementing synchronouse version of OnNavigatedTo and just mark void as async. There you have it - event like behaviour. But it seems quite counter intuitive to use async void when you have OnNavigatedToAsync ...
Example No.2:
Quite common scenario: before navigating from current page we want to prompt user whether he/she wants to save changes...
So here it's very simple:
public Task OnNavigatingFromAsync(OnNavigatingFromEventArgs e)
{
bool proceed = await myPrompt.ShowModalAsync();
if (proceed == false)
{
e.Cancel = true;
}
}
In case, OnNavigatingFrom was an event we could not prevent navigation while awaiting prompt, navigation would probably already completed.
So we could like e.Cancel = true is sync part, and then make navigation request again... (?)
Right now OnNavigat* methods are provided by corresponding interfaces. This means
NavigationServicecan await asynchronous versions of these methods (and actually is doing that at this point). That soultion has some pros and cons.Example No.1: Client wants to start downloading something after navigating to some page. What is the natural way to do that? Well isn't that just:
The problem with that is
NavigationServiceis awaiting that, and the navigation process is not getting finished beforeDownloadStuff()finishes. Obviously the navigation should have ended by that time. Of course this can be fixed by implementing synchronouse version ofOnNavigatedToand just markvoidasasync. There you have it - event like behaviour. But it seems quite counter intuitive to useasync voidwhen you haveOnNavigatedToAsync...Example No.2: Quite common scenario: before navigating from current page we want to prompt user whether he/she wants to save changes... So here it's very simple:
In case,
OnNavigatingFromwas an event we could not prevent navigation while awaiting prompt, navigation would probably already completed.So we could like
e.Cancel = trueis sync part, and then make navigation request again... (?)