Design Patterns - Problems and Solutions with Model-View-ViewModel. Windows Presentation Foundation (WPF) and Silverlight provide rich APIs for building modern applications, but understanding and applying all the WPF features in harmony with each other to build well-designed and easily maintained apps can be difficult. Where do you start? And what is the right way to compose your application? The Model-View-ViewModel (MVVM) design pattern describes a popular approach for building WPF and Silverlight applications. It’s both a powerful tool for building applications and a common language for discussing application design with developers.
When is the MVVM design pattern applicable, and when is it unnecessary? In this article I’ll explain how the ViewModel works, and discuss some benefits and issues involved in implementing a ViewModel in your code. Model, ViewModel and View Every WPF and Silverlight application I’ve worked on so far had the same high-level component design. Sitting atop the Model is the ViewModel. Why Use a ViewModel? Dynamic Properties. Appliquer la pattern MVVM avec MVVM Light. Read this article in your language IT | EN | DE | ES MVVM vous devez commencer à connaître, je vous en parle depuis un moment (notamment un très long article à télécharger, voir le billet MVVM avec Silverlight). Mais au-delà de la théorie comment mettre en pratique simplement cette pattern sous WPF et Silverlight ? La réponse se trouve dans ce nouvel article de plus de 90 pages ! Dans le précédent article sur MVVM, je vous ai montré de quoi MVVM était fait, et pour illustrer le propos je m’étais donné comme ligne directrice de réaliser des projets exemples uniquement avec ce qu’il y a “dans la boîte”, en choisissant Silverlight 4 comme support.
Cela a permis de mettre en évidence les points essentiels de la pattern MVVM et les difficultés que sa mise en œuvre entraîne. Mais comment appliquer réellement MVVM, concrètement j’entends, dans de vraies applications ? La réponse est non, que cela soit sous WPF ou Silverlight. Que du bonheur pour les longues soirées d’été ! Merci Dot.Blog ! Google + Silverlight MVVM : les commandes. Read this article in your language IT | EN | DE | ES Silverlight 4 ajoute la gestion des commandes à certains objets comme les boutons ce qui simplifie la mise en œuvre de la pattern MVVM.
Le lien entre Interface et ViewModel s’en trouve amélioré même si cela semble toujours un peu nébuleux pour le débutant. Il est vrai que programmer de la sorte impose de raisonner autrement. Nous allons le voir au travers d’un exemple. Le but Je ne vais pas me lancer dans un cours sur MVVM d’autant que j’ai déjà écrit un très long article sur la question il y a peu de temps sans compter les billets où j’y fais référence directement ou non.
Le but de ce billet est plutôt de partir d’un cas particulier pour voir la mise en œuvre d’un besoin courant sous MVVM, les commandes. Structure simplifiée d’une application MVVM Plutôt que des redites je renvoie ainsi le lecteur vers les billets et articles suivants pour qu’il puisse faire le point sur MVVM : un résumé Informations mais aussi commandes Un exemple live. Comprendre et Appliquer MVVM. THE MODEL-VIEW-VIEWMODEL (MVVM) DESIGN PATTERN FOR WPF. Patterns WPF Apps With The Model-View-ViewModel Design Pattern Josh Smith Developing the user interface of a professional software application is not easy. It can be a murky blend of data, interaction design, visual design, connectivity, multithreading, security, internationalization, validation, unit testing, and a touch of voodoo.
There are popular design patterns that can help to tame this unwieldy beast, but properly separating and addressing the multitude of concerns can be difficult. It is not always the design patterns at fault. As the software world continues to adopt WPF at an increasing rate, the WPF community has been developing its own ecosystem of patterns and practices. By the end of this article, it will be clear how data templates, commands, data binding, the resource system, and the MVVM pattern all fit together to create a simple, testable, robust framework on which any WPF application can thrive. Order vs. The Evolution of Model-View-ViewModel The Demo Application. Presentation Model. Represent the state and behavior of the presentation independently of the GUI controls used in the interface Also Known As: Application Model GUIs consist of widgets that contain the state of the GUI screen.
Leaving the state of the GUI in widgets makes it harder to get at this state, since that involves manipulating widget APIs, and also encourages putting presentation behavior in the view class. Presentation Model pulls the state and behavior of the view out into a model class that is part of the presentation. The Presentation Model coordinates with the domain layer and provides an interface to the view that minimizes decision making in the view. The view either stores all its state in the Presentation Model or synchonizes its state with Presentation Model frequently Presentation Model may interact with several domain objects, but Presentation Model is not a GUI friendly facade to a specific domain object. How it Works Figure 2: How objects react to clicking the classical check box. Model-View-ViewModel (MVVM) Explained. The purpose of this post is to provide an introduction to the Model-View-ViewModel (MVVM) pattern.
While I've participated in lots of discussions online about MVVM, it occurred to me that beginners who are learning the pattern have very little to go on and a lot of conflicting resources to wade through in order to try to implement it in their own code. I am not trying to introduce dogma but wanted to pull together key concepts in a single post to make it easy and straightforward to understand the value of the pattern and how it can be implemented.
MVVM is really far simpler than people make it out to be. Click here to read the Spanish version (Leer en español) Want to learn about MVVM in the HTML5 age? Why Even Care About MVVM? Why should you, as a developer, even care about the Model-View-ViewModel pattern? Do you need to share a project with a designer, and have the flexibility for design work and development work to happen near-simultaneously? Let's examine the pieces of the MVVM pie. Dependency Properties Overview. In WPF, properties are typically exposed as common language runtime (CLR) properties. At a basic level, you could interact with these properties directly and never know that they are implemented as a dependency property. However, you should become familiar with some or all of the features of the WPF property system, so that you can take advantage of these features. The purpose of dependency properties is to provide a way to compute the value of a property based on the value of other inputs.
These other inputs might include system properties such as themes and user preference, just-in-time property determination mechanisms such as data binding and animations/storyboards, multiple-use templates such as resources and styles, or values known through parent-child relationships with other elements in the element tree. Following is a summation of the terminology that is used in this software development kit (SDK) documentation when discussing dependency properties: Design Patterns: Model View Presenter. Data and WPF: Customize Data Display with Data Binding and WPF. Data and WPF Customize Data Display with Data Binding and WPF Josh Smith When the Windows® Presentation Foundation (WPF) first appeared on the .NET radar, most of the articles and demo applications touted its superb rendering engine and 3D capabilities.
While fun to read and play with, such examples do not demonstrate the powerful real-world functionality of WPF. Most of us do not need to create applications with rotating video cubes that burst into fireworks when you click on them. Most of us earn a living by creating software to display and edit large amounts of complex business or scientific data. The good news is that WPF offers excellent support for managing the display and editing of complex data.
Binding in Code One of the biggest changes that WPF introduces for desktop application developers is the extensive use of and support for declarative programming. In many situations, it is more convenient and expedient to declare bindings in XAML. Working with Templates. Data Binding (WPF) WPF avancé : Comprendre les événements et les commandes routés dans WPF. WPF avancé Comprendre les événements et les commandes routés dans WPF Brian Noyes Le plus décourageant, lorsque l'on souhaite se mettre à niveau dans l'utilisation de Windows® Presentation Foundation (WPF), est le grand nombre de nouvelles constructions qu'il faut apprendre à maîtriser. Même des choses simples telles que les propriétés et les événements de Microsoft® .NET Framework ont, dans WPF, de nouvelles contreparties avec des capacités ajoutées et, donc, la complexité qui en découle, en particulier les propriétés de dépendance et les événements routés.
Et, puis, il y a toutes les nouveautés, telles que les animations, les styles, les modèles de contrôle et les commandes routées. Il y a beaucoup à apprendre. Dans cet article, je me concentrerai sur deux éléments très importants dans la liste des nouveaux éléments à maîtriser de WPF. Aperçu des événements routés <Button Name="myButton" Click="myButton_Click">Click Me</Button> #line 6 "..\.. Arborescences d'éléments WPF Routage d'événement. Data Points: Data Binding in WPF. Data Points Data Binding in WPF John Papa Code download available at:DataPoints2007_12.exe(161 KB) By now, many of you know that Windows® Presentation Foundation (WPF) makes it easy to design robust user interfaces.
But what you probably didn't know is that it also provides powerful data-binding capabilities. Data Binding Specifics To use WPF data binding, you must always have a target and a source. Now let's take a look at how the WPF data-binding techniques work and I'll present practical examples that illustrate their use. Creating a Simple Binding Let's start with a simple example that illustrates how to bind a TextBlock's Text property to a ListBox's selected item. The code listed in Figure 1 can be modified slightly to use a shorthand syntax for data binding. This syntax, called the attribute syntax, condenses the data binding code inside of the Text attribute of the TextBlock. Binding Modes Figure 2 Binding a Source to Two Targets Figure 3 TwoWay Binding in Action A Time to Bind. Advanced Basics: The ObservableCollection Class. Advanced Basics The ObservableCollection Class Ken Getz Imagine that you're creating a Windows Forms application, and you have bound a DataGridView control to a standard List(Of Customer) data structure.
You'd like to be able to keep the items in the grid synchronized with the values in the underlying data source. That is, if some other code or some other form changes a customer's data in the List, you'd like the grid to update and display the modified data. Using Windows Forms, this feat is possible, in a very general sense. Although the ObservableCollection class makes it possible for WPF applications to keep bound controls in sync with underlying data sources, it provides even more useful information—specifically, the ObservableCollection class also raises the CollectionChanged event when you add, remove, move, refresh, or replace an item in the collection. Introducing the ObservableCollection Class Examining the Sample Figure 3 The Sample WPF Window (Click the image for a larger view)
Cutting Edge: Collections and Data Binding. Cutting Edge Collections and Data Binding Dino Esposito Code download available at:CuttingEdge0505.exe(159 KB) When it's time to design the Data Access Layer (DAL) of your distributed Microsoft® .NET Framework-based app, one of the key decisions you'll make is how you'll pass data to and from methods of DAL classes. There are quite a few options for passing business data to and from DAL classes, but in most real-world cases the choices boil down to just two—using DataSet objects or collections of custom business entity objects. The "Patterns and Practices" series of articles and books provide some guidance on the most commonly implemented practices. DataSets have built-in support for optimistic concurrency and the ability to define and handle complex relationships between tables. Data that DAL classes retrieve will often be bound to Windows® and Web Forms controls and also will often be used to serve Web services requests.
Collection Basics Fill the Collection A Word on Generics. Données et WPF : Personnalisez l'affichage des données avec la liaison de données et WPF. Données et WPF Personnalisez l'affichage des données avec la liaison de données et WPF Josh Smith Lorsque Windows® Presentation Foundation (WPF) est apparu pour la première fois sur le radar .NET, la plupart des articles et des applications de démonstration faisaient l'éloge de son moteur de rendu et de ses superbes capacités 3D.
Bien que ces exemples soient amusants à lire et à essayer, ils ne démontrent pas la puissance pratique des fonctionnalités de WPF. La plupart d'entre nous n'avons pas besoin de créer des applications avec des cubes vidéo pivotants qui explosent en feu d'artifice lorsque l'on clique dessus.
La plupart d'entre nous gagne son pain en créant des logiciels permettant d'afficher et d'éditer des grandes quantités de données métier ou scientifiques complexes. La bonne nouvelle est que WPF offre un excellent support de gestion de l'affichage et d'édition de données complexes. Lier dans du code Vous pouvez séparer facilement une propriété en utilisant le code indiqué ici : Charting with DataTemplates.
For WPF programmers, one major revelation about the power of the DataTemplate comes with a demonstration of how a little piece of XAML (Figure 1) can turn business objects into bar charts (Figure 2). Following the exhilaration at seeing the chart's rendering, the technique unfortunately seems to "stall out. " Enhancing the simple bar chart becomes awkward, and using data templates for other types of common charts -- such as pie charts and line charts -- seems nearly impossible. That's too bad, because using data templates in this way is simply too powerful a technique to be relegated to unadorned bar charts. In this article, I will show you a few techniques to get around the apparent limitations.
There will be some code involved to help out with the details that XAML can't manage by itself, but the code will often be generalized enough to use for other applications. The goal is always to keep enough of the visual design in XAML so that changes and experimentation are easy. Basic Concepts. Prism (Composite Application Guidance for WPF) Patterns & practices Developer Center June 2008 Prism (Composite Application Guidance for WPF) is designed to help you more easily build enterprise-level Windows Presentation Foundation (WPF) client applications. This guidance will help you design and build flexible composite WPF client applications-composite applications use loosely coupled, independently evolvable pieces that work together in the overall application. Prism (Composite Application Guidance for WPF) can help you develop your WPF client application in a modular fashion. With this approach, you manage the complexity of a large application by breaking it down into smaller, simpler modules.
This guidance is intended for software architects and developers who are building enterprise WPF client applications. This guidance was designed to run on the Microsoft Windows Vista, Windows XP Professional, or Windows Server 2003 operating system. Before you can use the Composite Application Library, the following must be installed: Composite Application Library.
Prism : Modèles pour la création d'applications composites avec WPF. Wpf - Good examples of MVVM Template. A Simple MVVM Example « Rachel Lim's Blog.