MVP is a variation of the Model-View-Controller pattern, which has been around for decades. For example, the Model-View-Presenter (MVP) pattern has enjoyed popularity on various UI programming platforms. Instead, you can happily exist in a state of controlled chaos, which is the natural state of affairs in most professional software development projects! The Evolution of Model-View-ViewModelĮver since people started to create software user interfaces, there have been popular design patterns to help make it easier. This approach helps avoid the cognitive chaos mentioned earlier. The names of certain classes include well-known terms from the MVVM pattern, such as ending with "ViewModel" if the class is an abstraction of a view. There is nothing wrong with either approach, but in this article, I examine the benefits of explicitly using MVVM as the architecture of a WPF application. We determine the name to apply to a piece of code by considering its functional role in the system.ĭevelopers often intentionally structure their code according to a design pattern, as opposed to letting the patterns emerge organically. We diminish the cognitive chaos of a complex system by applying well-known names to certain entities in the source code. Eventually, the complexity of a system, and the recurring problems it contains, encourages developers to organize their code in such a way that it is easier to comprehend, discuss, extend, and troubleshoot. However, as the number of features in a program increases, the number of lines of code and moving parts increase accordingly. Any competent developer can understand a few lines of code at a glance. It is unnecessary and counter productive to use design patterns in a simple "Hello, World!" program. Before diving into the details, let's review why you should use a pattern like MVVM in the first place. The unit tests in the demo solution show how easy it is to test the functionality of an application's user interface when that functionality exists in a set of ViewModel classes. The demonstration program that accompanies this article can serve as a template for a real WPF application that uses MVVM as its core architecture. By leveraging some core features of WPF in conjunction with the Model-View-ViewModel (MVVM) design pattern, I will walk through an example program that demonstrates just how simple it can be to build a WPF application the "right way."īy 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. In this article, I'll review some of those best practices for designing and implementing client applications with WPF. Fortunately, Windows Presentation Foundation (WPF) provides exactly that.Īs the software world continues to adopt WPF at an increasing rate, the WPF community has been developing its own ecosystem of patterns and practices. What's needed is a platform that makes it easy to build UIs using simple, time-tested, developer-approved design patterns. Sometimes we use complicated design patterns, which require writing a lot of code because the UI platform in use does not lend itself well to a simpler pattern. It is not always the design patterns at fault. The more complicated the patterns are, the more likely that shortcuts will be used later on which undermine all previous efforts to do things the right way. 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. Volume 24 Number 02 Patterns - WPF Apps With The Model-View-ViewModel Design Pattern
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