The app is live on the Windows Store and has a 8.0 version. If I re-target to Windows Phone 8.1 and publish with new features, will it be available for Windows Phone 8.0 users?
Most of our users are still on 8.0.
The user (OS/Store) downloads the most suitable package of the app. If user has WP8.1 and your app has a 8.1 package, then this will be installed, otherwise 8.0 app package will be downloaded.
From what you have written, you already have a working WP8.0 version of the app, now if you want to add some new features from 8.1 then, once you retarget the app, you have to add new package to your app when you are updating it. Do not replace the old working 8.0 package. Once you have added new package and it has passed certification, all users that have 8.0 version of your app and 8.1 OS version, will be prompted that there is an update available.
What is important:
you can retarget to both 8.1 Silverlight and Runtime (of course the second option needs some more changes and some things to be rewritten),
IsolatedStorage is preserved,
when you retarget to Runtime, you will have to parse IsoalatedStorageSettings from file in LocalStorage.
I've done similar thing with WP8.0 -> WP8.1 Runtime, I also recommend to test it on beta app, so you will be sure how it works.
If you re-target the app to Windows Phone 8.1, it'll be available to only Windows Phone 8.1 users. If you submit such an app to Store, it'll be displayed only in devices running Windows Phone 8.1.
However, you can submit two packages for same app in Windows Phone Store. So while submitting an update for your app, instead of replacing the existing Windows Phone 8.0 package, you can add another package for the Windows Phone 8.1 version which will have new features. The Windows Phone Store will ensure that it shows the correct XAP to correct OS version. This way, Windows Phone 8.1 users will be able take advantage of the new features, while Windows Phone 8.0 users will still be able to access the old app.
Going forward, if you want to support both OS versions, I'll suggest to keep a copy of Windows Phone 8.0 project before re-targeting to Windows Phone 8.1.
Yes, if you just re-target the project! But make sure you aren't using native WP 8.1 features, as they wouldn't work on WP8.
I've downloaded the Windows Phone 8.1 SDK Update and I'm attempting to make a Windows Phone 8.1 project. I've updated visual studio with the latest patches but the only template options I have for 8.1 is the standard Windows Store apps as seen in the screenshot below:
Windows Store
Any idea how I can get "Windows Phone" to appear with the appropriate OS target?
I think you didn't install everything. Because i've got actually another screenshot. Following this link you must install Visual Studio 2013 Update 2 - everything needed for WP8.1 is there. Also if you wish to develop Windows Store apps (universal or something) you should install Windows 8.1 SDK from here
Look a bit bown in the list on your screenshot. On the same level the 2nd last option is Windows Phone. That should be it.
I am working on Windows Phone development. For that I installed required SDK. I do create new project with Windows Phone 8.1, but gradually found that it don't support WCF service as we can not add service reference in assembly. After research I found that Windows Phone 8.1 doesn't support WCF services(refernce). Then I add new Silverlight Windows Phone 8.1 project and found that it support web service(Work Around). While development in Silverlight project I found that their is another difference between two type of project in syntax also, e.g. Navigation to another page,
Windows Phone 8.1 Silverlight support following syntax:
NavigationService.Navigate(new Uri(#"/SecondPage.xaml", UriKind.Relative));
where as Windows Phone 8.1 support(reference)
Frame.Navigate(typeof(SecondPage));
Now I am getting confuse with those type of project and unable to find those differences. Please help me out.
Silverlight navigates between pages using Uri that point to xaml
files.
Windows Phone Runtime (8.1 Store Apps) uses navigation with
pagetypes.
If your app is a Windows Phone Silverlight (8 or 8.1) App, you have to use the first approach for navigating between pages.
The other one simply isn't available to your project.
Windows Phone currently has multiple different application models available, which differ significantly. I know that can be quite confusing When looking for samples and guidance make sure the article you found is matching your app type (i.e. Silverlight).
How can i use that? In Windows Phone 8.1 project there is no System.Data namespace. In internet I could not found any documentation for SQLite to Windows Phone 8.1
You need to install SQLite extension. http://visualstudiogallery.msdn.microsoft.com/5d97faf6-39e3-4048-a0bc-adde2af75d1b
This tutorial might help too.
I am trying to create a background task in Windows phone application. However I am unable to add reference to Windows.ApplicationModel.Background dll. Where is it located and how to add?
It is not a part of the Windows Phone platform, it is part of the Windows Store platform.
MSDN - Windows.ApplicationModel.Background namespace