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Porting Windows Phone Silverlight business and data layers to UWP

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The previous topic was Porting for I/O, device, and app model.

Behind your UI are your business and data layers. The code in these layers calls operating system and .NET Framework APIs (for example, background processing, location, the camera, the file system, network, and other data access). The vast majority of those are available to a Universal Windows Platform (UWP) app, so you can expect to be able to port much of this code without change.

Asynchronous methods

One of the priorities of the Universal Windows Platform (UWP) is to enable you to build apps that are truly, and consistently, responsive. Animations are always smooth, and touch interactions such as panning and swiping are instantaneous and free of lag, making it feel like the UI is glued to your finger. To achieve this, any UWP API that can't guarantee to complete within 50ms has been made asynchronous and its name suffixed with Async. Your UI thread will return immediately from calling an Async method, and the work will take place on another thread. Consuming an Async method is made very easy, syntactically, using the C# await operator, JavaScript promise objects, and C++ continuations. For more info, see Asynchronous programming.

Background processing

A Windows Phone Silverlight app can use a managed ScheduledTaskAgent object to perform a task while the app is not in the foreground. A UWP app uses the BackgroundTaskBuilder class to create and register a background task in a similar way. You define a class that implements the work of your background task. The system runs your background task periodically, calling the Run method of your class to execute the work. In a UWP app, remember to set the Background Tasks declaration in the app package manifest. For more info, see Support your app with background tasks.

To transfer large data files in the background, a Windows Phone Silverlight app uses the BackgroundTransferService class. A UWP app uses APIs in the Windows.Networking.BackgroundTransfer namespace to do this. The features use a similar pattern to initiate transfers, but the new API has improved capabilities and performance. For more info, see Transferring data in the background.

A Windows Phone Silverlight app uses the managed classes in the Microsoft.Phone.BackgroundAudio namespace to play audio while the app is not in the foreground. The UWP uses the Windows Phone Store app model, see Background Audio and the Background audio sample.

Cloud services, networking, and databases

Hosting data and app services in the cloud is possible using Azure. See Getting Started with Mobile Services. For solutions that require both online and offline data see: Using offline data sync in Mobile Services.

The UWP has partial support for the System.Net.HttpWebRequest class, but the System.Net.WebClient class is not supported. The recommended, forward-looking alternative is the Windows.Web.Http.HttpClient class (or System.Net.Http.HttpClient if you need your code to be portable to other platforms that support .NET). These APIs use System.Net.Http.HttpRequestMessage to represent an HTTP request.

UWP apps do not currently include built-in support for data-intensive scenarios such as line of business (LOB) scenarios. However, you can make use SQLite for local transactional database services. For more info, see SQLite.

Pass absolute URIs, not relative URIs, to Windows Runtime types. See Passing a URI to the Windows Runtime.

Launchers and Choosers

With Launchers and Choosers (found in the Microsoft.Phone.Tasks namespace), a Windows Phone Silverlight app can interact with the operating system to perform common operations such as composing an email, choosing a photo, or sharing certain kinds of data with another app. Search for Microsoft.Phone.Tasks in the topic Windows Phone Silverlight to Windows 10 namespace and class mappings to find the equivalent UWP type. These range from similar mechanisms, called launchers and pickers, to implementing a contract for sharing data between apps.

A Windows Phone Silverlight app can be put into a dormant state or even tombstoned when using, for example, the photo Chooser task. A UWP app remains active and running while using the FileOpenPicker class.

Monetization (trial mode and in-app purchases)

A Windows Phone Silverlight app can use the UWP CurrentApp class for most of its trial mode and in-app purchase functionality, so that code doesn't need to be ported. But, a Windows Phone Silverlight app calls MarketplaceDetailTask.Show to offer the app for purchase:

    private void Buy()
    {
        MarketplaceDetailTask marketplaceDetailTask = new MarketplaceDetailTask();
        marketplaceDetailTask.ContentType = MarketplaceContentType.Applications;
        marketplaceDetailTask.Show();
    }

Port that code to call the UWP RequestAppPurchaseAsync method:

    private async void Buy()
    {
        await Windows.ApplicationModel.Store.CurrentApp.RequestAppPurchaseAsync(false);
    }

If you have code that simulates your app purchase and in-app purchase features for testing purposes, then you can port that to use the CurrentAppSimulator class instead.

Notifications for tile or toast updates

Notifications are an extension of the push notification model for Windows Phone Silverlight apps. When you receive a notification from the Windows Push Notification Service (WNS), you can surface the info to the UI with a tile update or with a toast. For porting the UI side of your notification features, see Tiles and toasts.

For more details on the use of notifications in a UWP app, see Sending toast notifications.

For info and tutorials on using tiles, toasts, badges, banners, and notifications in a Windows Runtime app using C++, C#, or Visual Basic, see Working with tiles, badges, and toast notifications.

Storage (file access)

Windows Phone Silverlight code that stores app settings as key-value pairs in isolated storage is easily ported. Here is a before-and-after example, first the Windows Phone Silverlight version:

    var propertySet = IsolatedStorageSettings.ApplicationSettings;
    const string key = "favoriteAuthor";
    propertySet[key] = "Charles Dickens";
    propertySet.Save();
    string myFavoriteAuthor = propertySet.Contains(key) ? (string)propertySet[key] : "<none>";

And the UWP equivalent:

    var propertySet = Windows.Storage.ApplicationData.Current.LocalSettings.Values;
    const string key = "favoriteAuthor";
    propertySet[key] = "Charles Dickens";
    string myFavoriteAuthor = propertySet.ContainsKey(key) ? (string)propertySet[key] : "<none>";

Although a subset of the Windows.Storage namespace is available to them, many Windows Phone Silverlight apps perform file i/o with the IsolatedStorageFile class because it has been supported for longer. Assuming that IsolatedStorageFile is being used, here's a before-and-after example of writing and reading a file, first the Windows Phone Silverlight version:

    const string filename = "FavoriteAuthor.txt";
    using (var store = IsolatedStorageFile.GetUserStoreForApplication())
    {
        using (var streamWriter = new StreamWriter(store.CreateFile(filename)))
        {
            streamWriter.Write("Charles Dickens");
        }
        using (var StreamReader = new StreamReader(store.OpenFile(filename, FileMode.Open, FileAccess.Read)))
        {
            string myFavoriteAuthor = StreamReader.ReadToEnd();
        }
    }

And the same functionality using the UWP:

    const string filename = "FavoriteAuthor.txt";
    var store = Windows.Storage.ApplicationData.Current.LocalFolder;
    Windows.Storage.StorageFile file = await store.CreateFileAsync(filename, Windows.Storage.CreationCollisionOption.ReplaceExisting);
    await Windows.Storage.FileIO.WriteTextAsync(file, "Charles Dickens");
    file = await store.GetFileAsync(filename);
    string myFavoriteAuthor = await Windows.Storage.FileIO.ReadTextAsync(file);

A Windows Phone Silverlight app has read-only access to the optional SD card. A UWP app has read-write access to the SD card. For more info, see Access the SD card.

For info about accessing photos, music, and video files in a UWP app, see Files and folders in the Music, Pictures, and Videos libraries.

For more info, see Files, folders, and libraries.

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