TinyMvvm is yet a small MVVM framework designed specifically with Xamarin Forms in mind.

This documentation does not cover the basics of MVVM and assumes that you are already familiar with the concept of MVVM.

Install the TinyMvvm.Forms package from NuGet, https://www.nuget.org/packages/TinyMvvm.Forms/

Install-Package TinyMvvm.Forms 

If you want to separate the ViewModels in a separate project that doesn't have references to Xamarin.Forms, just install the TinyMvvm package on that project.

Install-Package TinyMvvm 

// Option 1:
var navigationHelper = new NavigationHelper(this);
navigationHelper.RegisterView<MainView>("MainView");
		
// Option 2: Register single views		
var navigationHelper = new FormsNavigationHelper(this);		
navigationHelper.RegisterView("MainView", typeof(MainView));		
		
// Option 3: Register all views (pages) that is inherited from Page		
// The class name will be the key. To use this, you need to add using System.Reflection;		
var asm = typeof(App).GetTypeInfo().Assembly;		
navigationHelper.RegisterViewsInAssembly(asm);

// Option 4: For Xamarin.Forms Shell URL navigation. Option 1-3 can be combined with Option 4 because ShellNavigationHelper is a subclass of FormsNavigationHelper.
var navigationHelper = new ShellNavigationHelper();

ShellViewBase shoule be used when using Xamarin.Forms Shell. It should be used as with ViewBase, described below. But if you use ViewBase, it will not work with navigation paramters or query paramters.

Features (or drawbacks) of the ViewBase

• It strongly types the ViewModel as any class implementing INotifyPropertyChanged
• It creates the ViewModel for you if you inherit the ViewModel from ViewModelBase

The view should inherit from ViewBase<T> where T is the ViewModel. The ViewModel can be any class that implements INotifyPropertyChanged.

ViewBase<T> itself inherits from Xamarin.Forms.ContentPage and can be treated by Xamarin Forms as any page.

If you decide to use ViewModelBase as the base class for your view model and at the same time have the IoC resolver enabled, the the view will automatically create the view model for you when the view is created. Hence no need to inject the view model in the constructor and assign it manually. Feature or not, you decide.

An example of a typical page in TinyMvvm would look like this xaml copied from the sample app.

<?xml version="1.0" encoding="UTF-8"?>
<tinymvvm:ViewBase x:TypeArguments="viewmodels:MainViewModel" 
    xmlns="http://xamarin.com/schemas/2014/forms" 
    xmlns:viewmodels="clr-namespace:TinyMvvm.Forms.Sample.ViewModels;assembly=TinyMvvm.Forms.Samples"
    xmlns:tinymvvm="clr-namespace:TinyMvvm.Forms;assembly=TinyMvvm.Forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
    x:Class="TinyMvvm.Forms.Sample.Views.MainView">
    
	<ContentPage.Content>
        <StackLayout Margin="10,40">
            <Label Text="Hello World" />
            <Button Text="About" Command="{Binding NavigateTo}" CommandParameter="AboutView" />
        </StackLayout>
    </ContentPage.Content>
    
</tinymvvm:ViewBase>

What you need to do is:

• Define two namespaces (viewmodels and tinymvvm)
• Change the view type to tinymvvm:ViewBase
• Add a type argument pointing to your view model

The only thing that changes in the code behind is the base class.

public partial class MainView : TinyMvvm.Forms.ViewBase<MainViewModel>
{
    public MainView()
    {
        InitializeComponent();
    }
}

TinyMvvm also defines a base class for the view model called ViewModelBase.

Features (or drawbacks) of the ViewModelBase

• Wraps navigation for you through the INavigation interface (Implemented in TinyNavigation)
• Implements INotifyPropertyChanged for you
• Propagates life cycle events to the view (Initialize, OnAppearing, OnDisapparing)

Shell URL navigation:

await Navigation.NavigateToAsync("//home/messages/id=1");

Xamarin.Forms traditional:

await Navigation.NavigateToAsync("AboutView");

with parameter:

var myObject = new MyObject();

await Navigation.NavigateToAsync("AboutView", myObject);

or open as modal:

await Navigation.OpenModalAsync("AboutView");

With URL navigation you can pass query parameters. With TinyMvvm you can access them from the ViewModel via the QueryParameters property of ViewModelBase. QueryParameters is of type Dictionary<string, string>.

public override async Task Initialize()
{
	await base.Initialize();
	
	var id = QueryParameters["id"];
}

public override async Task Initialize()
{
	await base.Initialize();
	
	var myObject = NavigationParameter as MyObject;
}

Tiny Mvvm is not bound to any specific IoC provider. There are a provider for Autoface that you can install with the "TinyMvvm.Autoface" package.

Install-Package TinyMvvm.Autofac

TinyMvvm has a Resolver in it's core project. To use it you need to add on provider to it that implements the IResolver interface, for example our Autofac provider.

var container = builder.Build();
var resolver = new AutofacResolver(container);
Resolver.SetResolver(resolver);

var navigationHelper = Resolver.Resolve<INavigationHelper>();

TinyMvvm has an own implementation of ICommand that not has any references to Xamarin.Forms so you can use it in an library without reference Xamarin.Forms.

public ICommand WithParameter
{
      get
      {
                return new TinyCommand(async() =>
                {
                   //Do stuff
                });
      }
}

TinyMvvm has no messaging system built-in, we recommend you to take a look at TinyPubSub if you need messaging in your app.

Check out TinyPubSub for more detailed information about it.