How to navigate through windows with MVVM Light for WPF?

I usually use a ContentControl to display dynamic content. It's Content property is usually bound to a CurrentViewModel property in the parent ViewModel, and DataTemplates are used to tell WPF how to draw the child ViewModels.

To change views, simply change the CurrentViewModel property in the parent ViewModel

You can find an example at this article of mine

Eventually I did it this way.

Following the idea of o_q, I created NavigationWindow as MainWindow and changed all the the views to page.

Then, I created an inteface and a class which using Navigation:

    public interface INavigationService    {        event NavigatingCancelEventHandler Navigating;        void NavigateTo(Uri pageUri);        void GoBack();    }    public class NavigationService : INavigationService    {        private NavigationWindow _mainFrame;        #region Implementation of INavigationService        public event NavigatingCancelEventHandler Navigating;        public void NavigateTo(Uri pageUri)        {            if (EnsureMainFrame())            {                _mainFrame.Navigate(pageUri);            }        }        public void GoBack()        {            if (EnsureMainFrame()                && _mainFrame.CanGoBack)            {                _mainFrame.GoBack();            }        }        #endregion        private bool EnsureMainFrame()        {            if (_mainFrame != null)            {                return true;            }            _mainFrame = System.Windows.Application.Current.MainWindow as NavigationWindow;            if (_mainFrame != null)            {                // Could be null if the app runs inside a design tool                _mainFrame.Navigating += (s, e) =>                {                    if (Navigating != null)                    {                        Navigating(s, e);                    }                };                return true;            }            return false;        }    }

Then, in viewModelLocator I created all the const string nedded to store the paths to my views:

    public class ViewModelLocator    {        #region Views Paths        public const string FrontendViewPath = "../Views/FrontendView.xaml";        public const string BackendViewPath = "../Views/BackendView.xaml";        public const string StartUpViewPath = "../Views/StartUpView.xaml";        public const string LoginViewPath = "../Views/LoginView.xaml";        public const string OutOfOrderViewPath = "../Views/OutOfOrderView.xaml";        public const string OperativeViewPath = "../Views/SubViews/OperativeView.xaml";        public const string ConfigurationViewPath = "../Views/SubViews/ConfigurationView.xaml";        #endregion     }

In App.cs, in the Application_Startup event handler, with the help of Unity IoC I registered a singleton of NavigationService:

    public partial class App : System.Windows.Application    {        private static IUnityContainer _ambientContainer;        public static IServiceLocator AmbientLocator { get; private set; }        ...       private void Application_Startup(object sender, System.Windows.StartupEventArgs e)        {                     _ambientContainer =               new UnityContainer();           _ambientContainer.RegisterType<INavigationService, NavigationService>(new ContainerControlledLifetimeManager());           AmbientLocator = new UnityServiceLocator(_ambientContainer);           ServiceLocator.SetLocatorProvider(() => AmbientLocator);

Now, in my ViewModelLocator, I can register a "Galasoft" message to catch all the events and navigate to a page; in the constructor I have:

        public ViewModelLocator()        {            CreateMain();            CreateFrontend();            CreateBackend();            CreateStartUp();            CreateOperative();            CreateLogin();            CreateConfiguration();            CreateOutOfOrder();            // Set Startup Page...            ServiceLocator.Current.GetInstance<INavigationService>().NavigateTo(new Uri(StartUpViewPath, UriKind.Relative));            Messenger.Default.Register<MoveToViewMessage>(this, message =>            {                switch (message.StateInfo.StateType)                {                    case StateType.StartUpState:                        ServiceLocator.Current.GetInstance<INavigationService>().NavigateTo(new Uri(StartUpViewPath,UriKind.Relative));                        break;                    case StateType.LoginState:                        ServiceLocator.Current.GetInstance<INavigationService>().NavigateTo(new Uri(LoginViewPath, UriKind.Relative));                        break;                    case StateType.OperativeState:                        ServiceLocator.Current.GetInstance<INavigationService>().NavigateTo(new Uri(OperativeViewPath, UriKind.Relative));                        break;                    case StateType.ConfigurationState:                        ServiceLocator.Current.GetInstance<INavigationService>().NavigateTo(new Uri(ConfigurationViewPath, UriKind.Relative));                        break;                    case StateType.ClosedState:                    case StateType.OutOfOrderState:                        ServiceLocator.Current.GetInstance<INavigationService>().NavigateTo(new Uri(OutOfOrderViewPath, UriKind.Relative));                        break;                    default:                        ServiceLocator.Current.GetInstance<INavigationService>().NavigateTo(new Uri(StartUpViewPath, UriKind.Relative));                        break;                }            });        }

In this way I keep all the viewModels "ignorant"... they don't know anything about navigation, plus I don't have code behind.

If I need to navigate by using a button from a view I can resolve NavigationService from the connected viewModel and navigate to the Page I need.

And, most important thing, it works!

For a navigable application, you'll want your start up view to be a NavigationWindow instead of a Window

<NavigationWindow    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"    x:Class="MainWindow"    Title="My Application Title"    Height="300"    Width="400" />

Code behind:

using System.Windows.Navigation;public partial class MainWindow : NavigationWindow{    public MainWindow()    {        InitializeComponent();    }}

The MVVM Light view templates use Window, but as you have guessed, you can just change it. If you want to be able to navigate to and from this view, make it a Page.This is how you navigate:

<Page    x:Class="Page1"    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"    Title="Page1">    <Grid>        <!-- this button will navigate to another page -->        <Button            Content="Go to Page 2"            Click="Button_Click" />    </Grid></Page>

Code Behind:

using System.Windows;using System.Windows.Controls;public partial class Page1 : Page{    public Page1()    {        InitializeComponent();    }    private void Button_Click(object sender, RoutedEventArgs e)    {        // the Page class has a property "NavigationService" which allows you to navigate.        // you can supply the "Navigate" method with a Uri or an object instance of the page         base.NavigationService.Navigate(new Page2());    }}