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A Windows App SDK migration of the UWP PhotoLab sample app (C#)

  • Artikkeli

This topic is a case study of taking the C# UWP PhotoLab sample app, and migrating it to the Windows App SDK.

Begin by cloning the UWP sample app's repo, and opening the solution in Visual Studio.

Important

For considerations and strategies for approaching the migration process, and how to set up your development environment for migrating, see Overall migration strategy. It's particularly important to see What's supported when porting from UWP to WinUI 3 so that you can ensure that all the features you need for your app are supported before you attempt migration.

Install tools for the Windows App SDK

To set up your development computer, see Install tools for the Windows App SDK.

Important

You'll find release notes topics along with the Windows App SDK release channels topic. There are release notes for each channel. Be sure to check any limitations and known issues in those release notes, since those might affect the results of following along with this case study and/or running the migrated app.

Create a new project

In Visual Studio, create a new C# project from the Blank App, Packaged (WinUI 3 in Desktop) project template. Name the project PhotoLabWinUI, uncheck Place solution and project in the same directory. You can target the most recent release (not preview) of the client operating system.

Note

We'll be referring to the UWP version of the sample project (the one that you cloned from its repo) as the source solution/project. We'll be referring to the Windows App SDK version as the target solution/project.

The order in which we'll migrate the code

MainPage is an important and prominent piece of the app. But if we were to begin by migrating that, then we'd soon realize that MainPage has a dependency on the DetailPage view; and then that DetailPage has a dependency on the ImageFileInfo model. So for this walkthrough we'll take this approach.

  • We'll begin by copying over the asset files.
  • Then we'll migrate the ImageFileInfo model.
  • Next we'll migrate the App class (since that needs changes making to it that DetailPage, MainPage, and LoadedImageBrush will depend on).
  • Then we'll migrate the LoadedImageBrush class.
  • Then we'll begin migrating the views, starting with DetailPage first.
  • And we'll finish up by migrating the MainPage view.

Copy asset files

  1. In your target project in Visual Studio, in Solution Explorer, right-click the Assets folder, and add a new folder named Samples.

  2. In your clone of the source project, in File Explorer, locate the folder Windows-appsample-photo-lab > PhotoLab > Assets. You'll find seven asset files in that folder, together with a subfolder named Samples containing sample images. Select those seven asset files, and the Samples subfolder, and copy them to the clipboard.

  3. Also in File Explorer, now locate the corresponding folder in the target project that you created. The path to that folder is PhotoLabWinUI > PhotoLabWinUI > Assets. Paste into that folder the asset files and the subfolder that you just copied, and accept the prompt to replace any files that already exist in the destination.

  4. In your target project in Visual Studio, in Solution Explorer, with the Assets folder expanded, you'll see in the Samples folder the contents of the Samples subfolder (which you just pasted). You can hover the mouse pointer over the asset files. A thumbnail preview will appear for each, confirming that you've replaced/added the asset files correctly.

Migrate the ImageFileInfo model

ImageFileInfo is a model (in the sense of models, views, and viewmodels) that represents an image file, such as a photo.

Copy ImageFileInfo source code files

  1. In your clone of the source project, in File Explorer, locate the folder Windows-appsample-photo-lab > PhotoLab. In that folder you'll find the source code file ImageFileInfo.cs; that file contains the implementation of ImageFileInfo. Select that file, and copy it to the clipboard.

  2. In Visual Studio, right-click the target project node, and click Open Folder in File Explorer. This opens the target project folder in File Explorer. Paste into that folder the file that you just copied.

Migrate ImageFileInfo source code

  1. Make the following find/replacements (match case and whole word) in the ImageFileInfo.cs file that you just pasted.
  • namespace PhotoLab => namespace PhotoLabWinUI
  • Windows.UI.Xaml => Microsoft.UI.Xaml

Windows.UI.Xaml is the namespace for UWP XAML; Microsoft.UI.Xaml is the namespace for WinUI XAML.

Note

The Mapping UWP APIs to the Windows App SDK topic provides a mapping of UWP APIs to their Windows App SDK equivalents. The change we made above is an example of a namespace name change necessary during the migration process.

  1. Now confirm that you can build the target solution (but don't run yet).

Migrate the App class

  1. From the source project, in the <Application.Resources> element in App.xaml, find the following four lines. Copy them, and paste them into the target project.
<SolidColorBrush x:Key="RatingControlSelectedForeground" Color="White"/>
<!--  Window width adaptive breakpoints.  -->
<x:Double x:Key="MinWindowBreakpoint">0</x:Double>
<x:Double x:Key="MediumWindowBreakpoint">641</x:Double>
<x:Double x:Key="LargeWindowBreakpoint">1008</x:Double>

Note

Because the target project will use different (and simpler) navigation from the source project, there's no need to copy over any further code from the source project's App.xaml.cs.

  1. In the target project, App stores the main window object in its private field m_window. Later in the migration process (when we migrate the source project's use of Window.Current), it'll be convenient if that private field is instead a public static property. So replace the m_window field with a Window property, and change references to m_window, as shown below.
// App.xaml.cs
public partial class App : Application
{
    ...
    protected override void OnLaunched(Microsoft.UI.Xaml.LaunchActivatedEventArgs args)
    {
        Window = new MainWindow();
        Window.Activate();
    }

    public static MainWindow Window { get; private set; }
}
  1. Later in the migration process (when we migrate the code that displays a FileSavePicker), it'll be convenient if App exposes the main window's handle (HWND). So add a WindowHandle property, and initialize it in the OnLaunched method, as shown below.
// App.xaml.cs
public partial class App : Application
{
    ...
    protected override void OnLaunched(Microsoft.UI.Xaml.LaunchActivatedEventArgs args)
    {
        Window = new MainWindow();
        Window.Activate();
        WindowHandle = WinRT.Interop.WindowNative.GetWindowHandle(Window);
    }

    public static IntPtr WindowHandle { get; private set; }
}

Migrate the LoadedImageBrush model

LoadedImageBrush is a specialization of XamlCompositionBrushBase. The PhotoLab sample app uses the LoadedImageBrush class to apply effects to photos.

Reference the Win2D NuGet package

To support code in LoadedImageBrush, the source project has a dependency on Win2D. So we'll also need a dependency on Win2D in our target project.

In the target solution in Visual Studio, click Tools > NuGet Package Manager > Manage NuGet Packages for Solution... > Browse, and type or paste Microsoft.Graphics.Win2D. Select the correct item in search results, check the PhotoLabWinUI project, and click Install to install the package into that project.

Copy LoadedImageBrush source code files

Copy LoadedImageBrush.cs from the source project to the target project in the same way that you copied ImageFileInfo.cs.

Migrate LoadedImageBrush source code

  1. Make the following find/replacements (match case and whole word) in the LoadedImageBrush.cs file that you just pasted.
  1. Confirm that you can build the target solution (but don't run yet).

Migrate the DetailPage view

DetailPage is the class that represents the photo editor page, where Win2D effects are toggled, set, and chained together. You get to the photo editor page by selecting a photo thumbnail on MainPage. DetailPage is a model (in the sense of models, views, and viewmodels).

Copy DetailPage source code files

Copy DetailPage.xaml and DetailPage.xaml.cs from the source project to the target project in the same way that you copied files in previous steps.

Migrate DetailPage source code

  1. Make the following find/replacements (match case and whole word) in the DetailPage.xaml file that you just pasted.
  • PhotoLab => PhotoLabWinUI
  1. Make the following find/replacements (match case and whole word) in the DetailPage.xaml.cs file that you just pasted.
  • namespace PhotoLab => namespace PhotoLabWinUI
  • Windows.UI.Colors => Microsoft.UI.Colors
  • Windows.UI.Xaml => Microsoft.UI.Xaml
  1. For the next step, we'll make the change that's explained in ContentDialog, and Popup. So, still in DetailPage.xaml.cs, in the ShowSaveDialog method, immediately before the line ContentDialogResult result = await saveDialog.ShowAsync();, add this code.
if (Windows.Foundation.Metadata.ApiInformation.IsApiContractPresent("Windows.Foundation.UniversalApiContract", 8))
{
    saveDialog.XamlRoot = this.Content.XamlRoot;
}
  1. Still in DetailPage.xaml.cs, in the OnNavigatedTo method, delete the following two lines of code. Just those two lines; later in this case study, we'll reintroduce the back button functionality that we just removed.
...
SystemNavigationManager.GetForCurrentView().AppViewBackButtonVisibility =
    AppViewBackButtonVisibility.Visible;
...
SystemNavigationManager.GetForCurrentView().AppViewBackButtonVisibility = 
    AppViewBackButtonVisibility.Collapsed;
...
  1. For this step, we'll make the change that's explained in MessageDialog, and Pickers. Still in DetailPage.xaml.cs, in the ExportImage method, immediately before the line var outputFile = await fileSavePicker.PickSaveFileAsync();, add this line of code.
WinRT.Interop.InitializeWithWindow.Initialize(fileSavePicker, App.WindowHandle);

MainPage has dependencies on DetailPage, which is why we migrated DetailPage first. But DetailPage has dependencies on MainPage, too, so we won't be able to build yet.

Migrate the MainPage view

The main page of the app represents the view that you see first when you run the app. It's the page that loads the photos from the Samples folder that's built into the sample app, and displays a tiled thumbnail view.

Copy MainPage source code files

Copy MainPage.xaml and MainPage.xaml.cs from the source project to the target project in the same way that you copied files in previous steps.

Migrate MainPage source code

  1. Make the following find/replacements (match case and whole word) in the MainPage.xaml file that you just pasted.
  • PhotoLab => PhotoLabWinUI

  1. Still in MainPage.xaml, find the markup animations:ReorderGridAnimation.Duration="400", and delete that.

  2. Make the following find/replacements (match case and whole word) in the MainPage.xaml.cs file that you just pasted.

  • namespace PhotoLab => namespace PhotoLabWinUI
  • Windows.UI.Xaml => Microsoft.UI.Xaml
  1. For this step, we'll make the change that's explained in ContentDialog, and Popup. So, still in MainPage.xaml.cs, in the GetItemsAsync method, immediately before the line ContentDialogResult resultNotUsed = await unsupportedFilesDialog.ShowAsync();, add this code.
if (Windows.Foundation.Metadata.ApiInformation.IsApiContractPresent("Windows.Foundation.UniversalApiContract", 8))
{
    unsupportedFilesDialog.XamlRoot = this.Content.XamlRoot;
}
  1. Still in MainPage.xaml.cs, in the OnNavigatedTo method, delete the following line of code.
SystemNavigationManager.GetForCurrentView().AppViewBackButtonVisibility =
    AppViewBackButtonVisibility.Collapsed;

Later in this case study, we'll reintroduce the back button functionality that we just removed.

  1. Confirm that you can build the target solution (but don't run yet).

The PhotoLab sample app uses navigation logic to navigate initially to MainPage (and then between MainPage and DetailPage). For more info about Windows App SDK apps that need navigation (and those that don't), see Do I need to implement page navigation?.

So the changes we'll make next support that navigation.

  1. In MainWindow.xaml, delete the <StackPanel> element, and replace it with just a named <Frame> element. The result looks like this:
<Window ...>
    <Frame x:Name="rootFrame"/>
</Window>

  1. In MainWindow.xaml.cs, delete the myButton_Click method.

  2. Still in MainWindow.xaml.cs, add the following line of code to the constructor.

public sealed partial class MainWindow : Window
{
    public MainWindow()
    {
        this.InitializeComponent();
        rootFrame.Navigate(typeof(MainPage));
    }
}
  1. Confirm that you can build the target solution (but don't run yet).

Restoring back button functionality

  1. In DetailPage.xaml, the root element is a RelativePanel. Add the following markup inside that RelativePanel, immediately after the StackPanel element.
<AppBarButton x:Name="BackButton" Click="BackButton_Click" Margin="0,0,12,0">
    <SymbolIcon Symbol="Back"/>
</AppBarButton>
  1. In DetailPage.xaml.cs, add the following two lines of code to the OnNavigatedTo method, in the place indicated.
if (this.Frame.CanGoBack)
{
    BackButton.Visibility = Microsoft.UI.Xaml.Visibility.Visible;
}
else
{
    BackButton.Visibility = Microsoft.UI.Xaml.Visibility.Collapsed;
}
  1. Still in DetailPage.xaml.cs, add the following event handler.
private void BackButton_Click(object sender, Microsoft.UI.Xaml.RoutedEventArgs e)
{
    Frame.GoBack();
}

Test the migrated app

Now build the project, and run the app to test it. Select an image, set a zoom level, choose effects, and configure them.

See Also