Nuclex.Windows.Forms/ReadMe.md

• Status: Stable and mature. Several projects are using this library, and it has received extensive testing on Linux and Windows.

• Platforms: Cross-platform, developed on Linux but also tested and working without any known issues on Windows.

Nuclex.Windows.Forms

This is a lightweight MVVM framework for Windows Forms. It is based on the "convention over configuration" idea and requires zero configuration. Rather than set up view mappings and view model services, you can simply ask it to display a view model (ExampleViewModel) with its default view and it will figure out what the correct view is by name (i.e. ExampleForm).

There are unit tests for the whole library, so everything is verifiably working on all platforms tested (Linux, Windows, Raspberry).

MVVM

MVVM stands for Model-View-ViewModel. It is a way to design GUI applications that improves testability and keeps the UI separate from the business logic.

• The Model is the underlying data the application is working with, not designed in any way to facilitate any GUI display or editing

• The ViewModel is like an adapter - it presents the data in the model in a way that can be easily dealt with by the view. For example, sets of items may be exposed as BindingList<Item>.

• The View is the UI itself - for example, the main window or a modal dialog that is displayed would be a view, too. Each view has a connected ViewModel and the only code in the view class should be what directly handles the UI, like updating button states when the ViewModel signals a change.

Basic Design

This library implements the MVVM pattern through its WindowManager class:

The WindowManager keeps track of all open windows and their view models, so your basic Main() method, which normally looks like this:

[STAThread]
static void Main() {
  Application.EnableVisualStyles();
  Application.SetCompatibleTextRenderingDefault(false);
  Application.Run(new MainForm());
}

Now becomes this:

[STAThread]
static void Main() {
  Application.EnableVisualStyles();
  Application.SetCompatibleTextRenderingDefault(false);

  using(var windowManager = new WindowManager()) {
    Application.Run(windowManager.OpenRoot<MainViewModel>());
  }
}

As you can see, we no longer mention the MainForm by name, instead we ask the WindowManager to construct a new MainViewModel and also create a view that displays it.

It does so by using a "convention over configuration" approach, meaning it assumes that if you request a view for FlurgleSettingsViewModel, it will look for a view named FlurgleSettingsView, FlurgleSettingsForm, FlurgeSettingsWindow or FlurgleSettingsDialog class and try to construct an instance of that class.

Furthermore, if that class implements the IView interface, the view model will be assigned to its DataContext property, establishing the View/ViewModel relationship.

Adding an IoC Container

In the previous example, the view and its view model were constructed using Activator.CreateInstance() - a method provided by .NET that creates a new instance via a type's default constructor.

Most of the time, ViewModels have constructor parameters, however. For example to provide the ViewModel with the data it is supposed to be an adapter for. You can achieve that by constructing the ViewModel yourself and passing it to the WindowManager.OpenRoot() or WindowManager.ShowModal() methods.

A much better approach is to use a dependency injector - an IoC container with automatic constructor parameter injection. My favorite one is Ninject (due to its neat setup with a fluent interface), but you can use any container you wish, simply by inheriting your own WindowManager class:

public class NinjectWindowManager : WindowManager {

  public NinjectWindowManager(IKernel kernel, IAutoBinder autoBinder = null) :
    base(autoBinder) {
    this.kernel = kernel;
  }

  protected override object CreateInstance(Type type) {
    return this.kernel.Get(type);
  }

  private IKernel kernel;
}

Your NinjectWindowManager will now use IKernel.Get() to construct its ViewModels, allowing their constructors to require any services and instances you have set up in your Ninject kernel.

class MainViewModel {

  public MainViewModel(IMyService myService, IMySettings mySettings) {
  	// ...
  }

}