How to implement MVVM in Windows Phone 8.1 app (xaml)? - windows-phone-8

Question

Could anyone give an example of implementation? Is it done with ViewModel implementing INotifyPropertyChanged (and raising events, as it's done in Silverlight) or some other way? How is ViewModel bound to the view?
All examples I've found so far are incomplete or outdated (refer to Silverlight apps, not Xaml ones).

Answer 1

In the case of Windows RT I would advise to look towards PRISM. It provides really good modern development practices. You will get suitable navigation service, app lifecycle management, great MVVM support and very flexible view and ViewModels resolution mechanism.
You can easily add it to your project via NuGet.
It has pretty good documentation, so if you have any questions you can find an answer on MSDN or even download free book Prism for the Windows Runtime. Our team has successful experience in building projects using PRISM.

Answer 2

I currently use the following approach in my own Universal/W8.1/WP8.1 apps. This approach uses the RArcher WinRT Toolkit, which is an experimental toolkit based on the MVVM pattern.
It provides a way to maintain app state and you can use the ViewModelBase to implement INPC.
It also uses the Unity dependency injection container.
I'd start with making the ViewModelLocator an application-wide resource, so my Views can access it easily.
<Application.Resources>
<vm:ViewModelLocator x:Key="ViewModelLocator" />
</Application.Resources>
The view can use it like so:
<Page.DataContext>
<Binding Source="{StaticResource ViewModelLocator}" Path="MainViewModel" />
</Page.DataContext>
The ViewModelLocator looks like this:
public sealed class ViewModelLocator
{
public ViewModelLocator()
{
RegisterIoCBindings();
}
public IMainViewModel MainViewModel
{
get { return IocContainer.Get<IMainViewModel>(); }
}
private void RegisterIoCBindings()
{
IocContainer.Container.RegisterType(typeof(IMainViewModel), typeof(MainViewModel),
null, new ContainerControlledLifetimeManager());
}
}
The MainViewModel has the ViewModelBase as baseclass and implements the IMainViewModel:
public sealed class MainViewModel : ViewModelBase, IMainViewModel
{
private string myText;
[AutoState]
public string MyText
{
get { return myText; }
set
{
myText = value;
OnPropertyChanged();
}
}
public MainViewModel() // You can use constructor injection here
{
}
}
That is the basic setup. And as the others have stated, MVVM is a pattern and there a many ways to use it. I would say, use what feels good ;-)
If you like to know more about this approach, check out the toolkit and unity DI.

Answer 3

There is no difference, it's the same. Because MVVM is a pattern. You can implement it to your windows phone app easily. I'm using MVVM Light for my wp apps and EventToCommand behavior to raise events. I have an app open sourced on GitHub, you can check it out if you want.