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Version du 29 septembre 2021 à 11:10

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Description

Fully open source version of Prism including

MVVM
Commanding: DelegateCommand
Messaging: EventAggregator
Navigation
Dialog services
Modularity
Dependency injection

Prism 8 supports WPF, Xamarin Forms and UNO, but not Silverlight, Windows 8/8.1/WP8.1 or UWP.

Getting Started

Nuget packages

Prism.Core
Prism.Wpf
Prism.DryIoc Prism.Unity dependency injection containers

Prism Template Pack Visual Studio extension

Templates
- Prism Blank App (.NET Core) - target .NET Core 3.1
- Prism Blank App (WPF) - target .NET Framework 4.7.2
- Prism Blank App (Uno plateform)

Snippets
- propp property which notifies its changes
- cmd cmdfull delegate command
- cmdg cmgfull delegate command with parameter

App.xaml

Shell: the main / root window

App.xaml

<prism:PrismApplication x:Class="PrismFull.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:prism="http://prismlibrary.com/" >
</prism:PrismApplication>

App.xaml.cs

public partial class App
{
    protected override Window CreateShell()
    {
        return Container.Resolve<MainWindow>();
    }

    protected override void RegisterTypes(IContainerRegistry containerRegistry)
    { }
}

ViewModels

ViewModels/MyViewModel.cs

public class MyViewModel : BindableBase
{
    private string myProperty;

    public string MyProperty
    {
        get => myProperty;
        set => SetProperty(ref myProperty, value);
    }
}

ViewModelLocator

Used to automatically wire the DataContext of a view to an instance of a ViewModel using a standard naming convention.

MyView.xaml

<!-- automatically wire the DataContext of MyView to an instance of MyApp.ViewModels.MyViewModel -->
<UserControl x:Class="MyApp.Views.MyView"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:viewModels="clr-namespace:MyApp.ViewModels"
             xmlns:prism="http://prismlibrary.com/"
             mc:Ignorable="d"
             d:DataContext="{d:DesignInstance viewModels:MyViewModel}"
             prism:ViewModelLocator.AutoWireViewModel="True">

This convention assumes:

that ViewModels are in the same assembly as the view types
that ViewModels are in a .ViewModels child namespace
that Views are in a .Views child namespace
that ViewModel names correspond with View names and end with ViewModel

Change the naming convention

App.xaml.cs

Custom ViewModel registration

Faster because it doesn't use reflexion.

ModuleAModule.cs

Commanding

MyViewModel.cs

public DelegateCommand DoCommand { get; }
public DelegateCommand DoWithParamCommand<string> { get; }

public MyViewModel()
{
    DoCommand = new DelegateCommand(Do, CanDo);
    DoWithParamCommand = new DelegateCommand<string>(DoWithParam, CanDoWithParam);
}

private void Do() { }
private bool CanDo() => true;

private void DoWithParam(string parameter) { }
private bool CanDoWithParam(string parameter) => true;

MyView.xaml

<Button Command="{Binding DoCommand}"
        Content="Do" />

<Button Command="{Binding DoWithParamCommand}"
        CommandParameter="{Binding Content, RelativeSource={RelativeSource Self}}}"
        Content="Do" />

RaiseCanExecuteChanged

private bool isEnabled;

public bool IsEnabled
{
    get => isEnabled;
    set
    {
         SetProperty(ref isEnabled, value);
         this.DoCommand.RaiseCanExecuteChanged();
    }
}

ObservesProperty

Whenever the value of the supplied property changes, the DelegateCommand will automatically call RaiseCanExecuteChanged to notify the UI of state changes.

DoCommand = new DelegateCommand(Do, CanDo).ObservesProperty(() => IsEnabled);

ObservesCanExecute

If your CanExecute is the result of a simple Boolean property, you can eliminate the need to declare a CanExecute delegate, and use the ObservesCanExecute method instead. ObservesCanExecute will not only send notifications to the UI when the registered property value changes but it will also use that same property as the actual CanExecute delegate.

DoCommand = new DelegateCommand(Do).ObservesCanExecute(() => IsEnabled);

Task-Based DelegateCommand

DoCommand = new DelegateCommand(DoAsync);

async void DoAsync()
{
    await SomeAsyncMethod();
}

Composite command

Parent command to multiple child commands.

Core/Commands/IApplicationCommands.cs

Core/Commands/ApplicationCommands.cs

App.xaml.cs

ViewModels/MainWindowViewModel.cs

ModuleA/ViewModels/ViewAViewModel.cs

Dependency Injection

App.xaml.cs

public partial class App
{
    protected override void RegisterTypes(IContainerRegistry containerRegistry)
    {
        // register a singleton service
        containerRegistry.RegisterSingleton<IMyService, MyService>();
        // registera transient service
        containerRegistry.Register<IMyService, MyService>();
    }

singleton service	for a service which is used throughout the application and that retains its state.
transient service	create a new instance each time.
scoped service	no implementation because unlike a web application, desktop applications are dealing with a single user and not scoped user requests.

Region

Region: placeholder for dynamic content where views will be injected.
Region manager: maintains a collection of all the regions of the application. Used for:
- create and define regions
- access to regions
- region navigation
- views composition

<ContentControl prism:RegionManager.RegionName="MyRegion" />

Region adapter

Adapts a view to a region.

Prism provides 3 region adapters:

ContentControlRegionAdapter allow to inject a view in a ContentControl
ItemsControlRegionAdapter allow to inject a view in an ItemsControl
SelectorRegionAdapter allow to inject a view in a ComboBox ListBox Ribbon TabControl

Other controls require a custom region adapter.

Core/Regions/StackPanelRegionAdapter.cs

App.xaml.cs

protected override void ConfigureRegionAdapterMappings(RegionAdapterMappings regionAdapterMappings)
{
    base.ConfigureRegionAdapterMappings(regionAdapterMappings);

    regionAdapterMappings.RegisterMapping<StackPanel>(Container.Resolve<StackPanelRegionAdapter>());
}

View discovery

Region looks for view type.

ModuleAModule.cs

public void OnInitialized(IContainerProvider containerProvider)
{
    this.regionManager.RegisterViewWithRegion("MyRegion", typeof(ViewA));
}

View injection

ModuleAModule.cs

public void OnInitialized(IContainerProvider containerProvider)
{
    var viewA = containerProvider.Resolve<ViewA>();
    var contentRegion = this.regionManager.Regions["ContentRegion"];
    contentRegion.Add(viewA);

    contentRegion.Add(anotherView);       // add another view to the region
    contentRegion.Activate(anotherView);  // tell the region to display this view

    contentRegion.Deactivate(anotherView);  // tell the region not to display this view anymore
}

Navigation

Move between views in a region based on url.
By default create a new instance a the view before to navigate to it or reuse the existing one (discriminate by view type) if it has already been created.

ModuleAModule.cs

public void RegisterTypes(IContainerRegistry containerRegistry)
{
    // register the ViewA under the unique string key ViewA (type of the view by default)
    containerRegistry.RegisterForNavigation<ViewA>();
    containerRegistry.RegisterForNavigation<ViewB>();

    // associate a view-model while register
    containerRegistry.RegisterForNavigation<ViewA, ViewAViewModel>();
}

ViewAViewModel.cs

internal sealed class ViewAViewModel : BindableBase, INavigationAware
{
    public void OnNavigatedTo(NavigationContext navigationContext)
    {
        var id = navigationContext.Parameters.GetValue<int>("id");
        var key = navigationContext.Parameters.GetValue<string>("key");
    }

    public void OnNavigatedFrom(NavigationContext navigationContext)
    { }

    // true  → reuse the existing instance
    // false → create a new instance 
    public bool IsNavigationTarget(NavigationContext navigationContext) => true;
}

Views/MainWindow.xaml

<Button Command="{Binding NavigateCommand}"
        CommandParameter="ViewA"
        Content="Navigate to A" />
<Button Command="{Binding NavigateCommand}"
        CommandParameter="ViewB  "
        Content="Navigate to B" />

ViewModels/MainWindowViewModel.cs

private readonly IRegionManager regionManager;

public DelegateCommand<string> NavigateCommand { get; private set; }

public MainWindowViewModel(IRegionManager regionManager)
{
    this.regionManager = regionManager;
    this.NavigateCommand = new DelegateCommand<string>(Navigate);
}

private void Navigate(string uri)
{
    var navigationParameters = new NavigationParameters();
    navigationParameters.Add("key", "value");

    this.regionManager.RequestNavigate("ContentRegion", $"{uri}?id=1", navigationParameters);
}

Confirm navigation request

ViewAViewModel.cs

internal sealed class ViewAViewModel : BindableBase, IConfirmNavigationRequest
{
    public void ConfirmNavigationRequest(NavigationContext navigationContext, Action<bool> continuationCallBack)
    {
        var continueNavigation = true;
        continuationCallBack(continueNavigation);
    }
}

Navigation journal

ViewAViewModel.cs

internal sealed class ViewAViewModel : BindableBase, INavigationAware
{
    private IRegionNavigationJournal journal;

    public DelegateCommand GoBackCommand { get; set; }

    public ViewAViewModel()
    {
        GoBackCommand = new DelegateCommand(GoBack);
    }

    public void OnNavigatedTo(NavigationContext navigationContext)
    {
        journal = navigationContext.NavigationService.Journal;
    }

    private void GoBack() => journal.GoBack();
}

Navigation with TabControl

MainWindow.xaml

MainWindowViewModel.cs

Modules

A module represents a functional responsability of the application (independent feature).

Add → New Project → WPF UserControl Library
Remove AssemblyInfo.cs and UserControl1.xaml
Add Prism.Wpf Nuget package

ModuleAModule.cs

public sealed class ModuleAModule : IModule
{
    public void OnInitialized(IContainerProvider containerProvider)
    { }

    public void RegisterTypes(IContainerRegistry containerRegistry)
    { }
}

Module catalog

Collection of modules that the application is going to load.

Code base

Hard reference to the modules.

App.xaml.cs

App.config

More loosely coupled approach.

App.xaml.cs

App.config

REM ModuleA post build event
xcopy /y "$(TargetDir)*.*" "$(SolutionDir)$(SolutionName)\$(OutDir)"

XAML resource dictionary

Event Aggregator

Loosely coupled event-based communication.
Event mechanism that enables communications between loosely coupled components in the application.

MyApp.Core/MyPayload.cs

public sealed class MyPayload
{
    public string Prop1 { get; set; }
    public string Prop2 { get; set; }
}

MyApp.Core/MyEvent.cs

public sealed class MyEvent : PubSubEvent<MyPayload>
{ }

MyApp/MyViewModel.cs

internal sealed class MyViewModel
{
    IEventAggregator eventAggregator;

    public MyViewModel(IEventAggregator eventAggregator)
    {
        this.eventAggregator = eventAggregator;
    }

    // publishing an event
    var payload = new MyPayload
    {
        Prop1 = "value1",
        Prop2 = "value2",
    };
    eventAggregator.GetEvent<MyEvent>().Publish(payload);

    // subscribing to events
    eventAggregator.GetEvent<MyEvent>().Subscribe(MyAction);
    void MyAction(MyPayload payload)
    { }
}

Subscribing on the UI Thread

If the subscriber needs to update UI elements in response to events, subscribe on the UI thread. In WPF, only a UI thread can update UI elements.

eventAggregator.GetEvent<MyEvent>().Subscribe(DisplayMessage, ThreadOption.UIThread);

PublisherThread	use this setting to receive the event on the publishers' thread. Default value.
UIThread	use this setting to receive the event on the UI thread.
BackgroundThread	use this setting to asynchronously receive the event on a .NET Framework thread-pool thread.

Subscription Filtering

eventAggregator.GetEvent<MyEvent>().Subscribe(MyAction, ThreadOption.PublisherThread, false, x => x.Prop1 == "KeyMessage");

Performance concern

var keepSubscriberReferenceAlive = true;
var myEvent = eventAggregator.GetEvent<MyEvent>();

myEvent.Subscribe(MyAction, keepSubscriberReferenceAlive);
myEvent.Unsubscribe(MyAction);

SubscriptionToken token = myEvent.Subscribe(MyAction, keepSubscriberReferenceAlive);
myEvent.Unsubscribe(token);

keepSubscriberReferenceAlive
true	the event instance keeps a strong reference to the subscriber instance, thereby not allowing it to get garbage collected.
false	default value. The event maintains a weak reference to the subscriber instance, thereby allowing the garbage collector to dispose the subscriber instance when there are no other references to it. When the subscriber instance gets collected, the event is automatically unsubscribed.

Dialog

Popup window displayed over the current application.

ViewModels/ViewAViewModel.cs

Dialogs/MessageDialog.xaml

Dialogs/MessageDialogViewModel

ModuleAModule.cs

@@ Ligne 474 : / Ligne 474 : @@
      </Grid>
 </Window>
+</filebox>
+<filebox fn='MainWindowViewModel.cs' collapsed>
+public class MainWindowViewModel : ViewModelBase
+{
+    private readonly IRegionManager _regionManager;
+    public DelegateCommand<string> NavigateCommand { get; set; }
+    public MainWindowViewModel(IRegionManager regionManager)
+    {
+        _regionManager = regionManager;
+        NavigateCommand = new DelegateCommand<string>(Navigate);
+    }
+    void Navigate(string navigationPath)
+    {
+        _regionManager.RequestNavigate("TabRegion", navigationPath);
+    }
+}
 </filebox>

« Prism 8 » : différence entre les versions

Version du 29 septembre 2021 à 11:10

Links

Description

Getting Started

Nuget packages

Prism Template Pack Visual Studio extension

App.xaml

ViewModels

ViewModelLocator

Change the naming convention

Custom ViewModel registration

Commanding

RaiseCanExecuteChanged

ObservesProperty

ObservesCanExecute

Task-Based DelegateCommand

Composite command

Dependency Injection

Region

Region adapter

View discovery

View injection

Navigation

Confirm navigation request

Navigation journal

Navigation with TabControl

Modules

Module catalog

Code base

App.config

Directory

XAML resource dictionary

Event Aggregator

Subscribing on the UI Thread

Subscription Filtering

Performance concern

Dialog