patterns & practices Symposium 2013

Tips for building a Windows Store app using XAML and C#: The Kona project

Francis Cheungfcheung@microsoft.com

Kona C# Background Tips and Lessons

Learned for building C# Windows Store apps

Agenda

• Modularity• UI Composition• Region

Navigation• Decoupled

Communication• Commands• MVVM Support

Prism for WPF, Silverlight and Windows Phone

End-to-end shopping app sample that provides guidance to C# developers on how to use modern C#, asynchronous programming, XAML, and the .NET for Windows Store apps to build a world-ready app for the global market. Projected to ship March 2013

The Kona Project

Rethink Prism Scenarios for Windows Store • Modularity

• UI Composition• Region Navigation• Decoupled

Communication• Commands• MVVM Support

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Walkthrough

Demo AdventureWorks Shopper

Tips and Lessons Learned

1. Leverage background in Windows Phone developmentWindows Phone apps Windows Store apps

Deactivate/Tombstoned/Reactivate Suspend/Terminate/Resume

Microsoft Push Notification Service (MPN)

Windows Push Notification Service (WNS)

Windows Phone Marketplace certification

Windows Store app certification & Application Excellence Review (AER)

App manifest declares capabilities App manifest declares capabilities

2. Focus on AttachedBehaviors• No Blend

Behavior<T>• No

BindingExpressions• Break out your

AttachedBehavior experience and ROCK ON!

3. Push Notification requires Windows Store registration

• Make sure to register your app with the Windows Store to get proper credentials (SID & secret key)

• Purely sideloaded apps won’t be able to receive notifications from Windows Notification Service (WNS)

1: async Task<int> AccessTheWebAsync()

2: {

3: HttpClient client = new HttpClient();

4: Task<string> getStringTask = client.GetStringAsync("http://msdn.microsoft.com");

5: DoIndependentWork();

6:

7: string urlContents = await getStringTask;

8: return urlContents.Length;

9: }

4. async & await are your friends

Pages and Navigation

Navigation supportprotected virtual void GoHome(object sender, RoutedEventArgs e)protected virtual void GoBack(object sender, RoutedEventArgs e)protected virtual void GoForward(object sender, RoutedEventArgs e)

Visual state switchingpublic void StartLayoutUpdates(object sender, RoutedEventArgs e)public void StopLayoutUpdates(object sender, RoutedEventArgs e)

Process lifetime managementprotected override void OnNavigatedTo(NavigationEventArgs e)protected override void OnNavigatedFrom(NavigationEventArgs e)protected virtual void LoadState(Object navigationParameter, Dictionary<String, Object> pageState)protected virtual void SaveState(Dictionary<String, Object> pageState)

5. Use the LayoutAwarePage class to provide navigation, state management, and visual state management

XAML:

<Button Click="GoBack" IsEnabled="{Binding Frame.CanGoBack, ElementName=pageRoot}" Style="{StaticResource BackButtonStyle}"/>

<UserControl Loaded="StartLayoutUpdates" Unloaded="StopLayoutUpdates">

Navigation & Visual State Support

protected override void SaveState(System.Collections.Generic.Dictionary<string, object> pageState){ var virtualizingStackPanel =

VisualTreeUtilities.GetVisualChild<VirtualizingStackPanel>(itemGridView);

if (virtualizingStackPanel != null && pageState != null) { pageState["virtualizingStackPanelHorizontalOffset"] = virtualizingStackPanel.HorizontalOffset; }}

protected override void LoadState(object navigationParameter, System.Collections.Generic.Dictionary<string, object>

pageState){ if (pageState != null && pageState.ContainsKey("virtualizingStackPanelHorizontalOffset")) { double.TryParse(pageState["virtualizingStackPanelHorizontalOffset"].ToString(), out virtualizingStackPanelHorizontalOffset); }}

LoadState & SaveState: SuspensionManager

<VisualStateManager.VisualStateGroups> <VisualStateGroup x:Name="ApplicationViewStates"> <VisualState x:Name="FullScreenLandscape"/> <VisualState x:Name="Filled"/> <VisualState x:Name="FullScreenPortrait"> <Storyboard> ... </Storyboard> </VisualState> <VisualState x:Name="Snapped"> <Storyboard> ... </Storyboard> </VisualState> </VisualStateGroup></VisualStateManager.VisualStateGroups>

6. Support visual state for landscape, portrait, fill, and snap

World Ready

7. Separate resources for each locale

<ToolTip x:Uid=“PreviewCartoonizeAppBarButtonToolTip” Content=“Preview Cartoonization” … />

Model-View-ViewModel Pattern

View First:this.Frame.Navigate(typeof(ItemDetailPage), itemId);

ViewModel First:Var itemDetailPageViewModel = new ItemDetailPageViewModel(…)

{ ItemId = itemId };navigationService.Navigate(itemDetailPageViewModel);

8. Navigation: View or ViewModel First

Nicki says: Neither!

String based navigation, like

URL’s!navigationService.Navigate( “ItemDetails”, itemId);

public abstract class BindableBase : INotifyPropertyChanged{ public event PropertyChangedEventHandler PropertyChanged;

protected bool SetProperty<T>(ref T storage, T value, [CallerMemberName] String propertyName = null) { if (object.Equals(storage, value)) return false; storage = value; this.OnPropertyChanged(propertyName); return true; }

protected void OnPropertyChanged([CallerMemberName] string propertyName = null) { var eventHandler = this.PropertyChanged; if (eventHandler != null) { eventHandler(this, new PropertyChangedEventArgs(propertyName)); } }}

9. Use BindableBase class to provide INPC

10. Use the Kona ViewModelLocator• Convention based lookup

• MyNamespace.MyPage -> MyNamespace.MyPageViewModel• Ability to override convention with exceptions to rule• Can leverage container to instantiate ViewModels.

XAML (attached property):konaInfrastructure:ViewModelLocator.AutoWireViewModel="true"

Typical Validation in WPF/Silverlight

• Implement INotifyDataErrorInfo• UI controls bind to errors dictionary if

NotifyOnValidationError=True

<TextBox Text="{Binding Id, Mode=TwoWay, ValidatesOnExceptions=True, NotifyOnValidationError=True}"/>

View:<TextBox

Text="{Binding Address.FirstName, Mode=TwoWay}" behaviors:HighlightFormFieldOnErrors.PropertyErrors="{Binding Errors[FirstName]}" />

ViewModel:_bindableValidator = new BindableValidator(_address);

public BindableValidator Errors{ get { return _bindableValidator; }}

11. Use Kona BindableValidator

Decoupled Eventing• Hollywood Parent style UI

Composition (user control)• Child control needs to listen to

events raised by long lived services but no way to unhook…

• Ported Prism EventAggregator

12. Use EventAggregator when necessarypublic SubscriberViewModel(IEventAggregator eventAggregator){ eventAggregator.GetEvent<ShoppingCartUpdatedEvent>()

.Subscribe(s => UpdateItemCountAsync());}

public PublisherViewModel(IEventAggregator eventAggregator){ _eventAggregator = eventAggregator;}

_eventAggregator.GetEvent<ShoppingCartUpdatedEvent>().Publish(string.Empty);

Commanding vs ViewModel Method InvocationICommand:

void Execute(object)bool CanExecute(object)event EventHandler CanExecuteChanged

Command Invoker:ButtonBase

-----------------------------------------------------Event -> Action

13. Use DelegateCommand for controls that support ICommandView:<Button Content=“Go to shopping cart” Command="{Binding ShoppingCartNavigationCommand}" />

ViewModel:ShoppingCartNavigationCommand = new DelegateCommand(NavigateToShoppingCartPage,

CanNavigateToShoppingCartPage);

ShoppingCartNavigationCommand.RaiseCanExecuteChanged();

14. Use AttachedBehaviors and Actions for the restView:<GridView x:Name="itemGridView“

ItemsSource="{Binding Source={StaticResource groupedItemsViewSource}}"

ItemTemplate="{StaticResource KonaRI250x250ItemTemplate}"SelectionMode="None“ IsItemClickEnabled="True"behaviors:ListViewItemClickedToAction.Action=

"{Binding CategoryNavigationAction}">

ViewModel:CategoryNavigationAction = NavigateToCategory;

Suspend, Resume, and Terminate

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15. Use Kona RestorableStateAttribute and MVVM frameworkpublic class MyViewModel : ViewModel, INavigationAware{ private string _name;

[RestorableState] public string Name

{ get { return _name; } set { SetProperty(ref _name, value); } }}

16. Unit Testing nicely integrated into VS2012

WP7: Jeff Wilcox's Silverlight Unit Test Framework• Tests run in emulator or device

Unit Test Library (Windows Store apps)• Run and debug from IDE• Can run tests from command line and export as trx format.

<ItemGroup> <TestAppPackages Include="$(MSBuildProjectDirectory)\..\Source\**\*.appx" /></ItemGroup> <Target Name="Test"> <Exec ContinueOnError="true" Command="vstest.console.exe /InIsolation /logger:trx %(TestAppPackages.Identity)" /></Target>

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17. File System Local Data (SQLite)

Roaming Data

Hi Priority Roaming Data

Password Vault

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Thanks! http://konaguidance.codeplex.com

fcheung@microsoft.com