CODEWITHSUNDEEP
windows-phone-7mvvmnavigationassemblies
Mark Wager-Smith
Mark Wager-Smith

Reputation: 75

How to detect back button -vs- GoBack() in WP7 app

Maybe I'm over-thinking this, but here's what I'm trying to accomplish.

I have two MVVM projects (assemblies) in my WP7 app. One page in the main project will call another page in the second project. The second page will allow the user to browse through a list of files on the web and select one to be downloaded to Isolated Storage. The files are rather small.

For a little background: I want two assemblies because this file-selection feature is not used often in the app and I want the Main assembly to be as small as possible to decrease startup time. I also want to be able to re-use this file-selection/download component in other apps.

The simple thing I'm trying to figure out is that when the user selects the file and it is downloaded, I will execute a GoBack() to return to the calling page. On the calling page, I need to know if, in fact, the user downloaded a file or if they cancelled out of the operation by simply hitting the back button. I thought the obvious thing might be to just check for the existence of the file in Isolated storage, but that just feel like a bit of a kludge to me.

I also thought about the Messenger, but I'm not sure how that would work across two assemblies.

Any advice would be appreciated.

Thanks

Upvotes: 1

Views: 464

Answers (1)

poppastring
poppastring

Reputation: 317

It is tough to know without looking at the code. However, I would suggest that you could pass back a value to the page depending on whether you successfully downloaded your file. Navigate with the value as follows (pass true or false depending on download success):

NavigationService.Navigate(new Uri(("/Page.xaml?download=true", UriKind.Relative));

Then evaluate the page in the destination as follows:

string download = "";
if (NavigationContext.QueryString.TryGetValue("download", out imageurl))
{
}

Upvotes: 1

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