Prism 8

Links

• Prism Library Documentation

Description

Fully open source version of Prism including MVVM, dependency injection, commands, EventAggregator, and others.
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 Template Pack Visual Studio extension

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.

Commands

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" />

Parameter can't be of value type (int, double, bool, etc). Use instead the equivalent nullable type.

RaiseCanExecuteChanged

private bool isEnabled; public bool IsEnabled { get => isEnabled; set { SetProperty(ref isEnabled, value); SubmitCommand.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(); }

Event Aggregator

Event mechanism that enables communications between loosely coupled components in the application.

MyApp.Shared/MyEvent.cs

public class MyEvent : PubSubEvent<string> { }

MyApp/MyViewModel.cs

internal sealed class MyViewModel { IEventAggregator eventAggregator; public MyViewModel(IEventAggregator eventAggregator) { this.eventAggregator = eventAggregator; } // publishing an event eventAggregator.GetEvent<MyEvent>().Publish("My message"); // subscribing to events eventAggregator.GetEvent<MyEvent>().Subscribe(DisplayMessage); void DisplayMessage(string message) { } }