Implement a NavigationService for MVVM in Metro Applications

   1: public class NavigationService : INavigationService

   2: {

   3:     protected Frame RootFrame { get; private set; }

   4:  

   5:     public NavigationService()

   6:     {

   7:         this.RootFrame = new Frame();

   8:     }

   9:  

  10:     public void Initialize(Window window, bool activate = true)

  11:     {

  12:         if (window.Content == null)

  13:             window.Content = this.RootFrame;

  14:  

  15:         if (activate)

  16:             window.Activate();

  17:     }

  18:  

  19:     public virtual void Navigate(Type destination, object parameter = null)

  20:     {

  21:         // avoid navigation if current equals to destination

  22:  

  23:         if (this.RootFrame.CurrentSourcePageType != destination)

  24:             this.RootFrame.Navigate(pageType, parameter);

  25:     }

  26:  

  27:     public virtual void GoBack()

  28:     {

  29:         if (this.RootFrame.CanGoBack)

  30:             this.RootFrame.GoBack();

  31:     }

  32:     

  33:     public virtual void GoForward()

  34:     {

  35:         if (this.RootFrame.CanGoForward)

  36:             this.RootFrame.GoForward();

  37:     }

  38:     

  39:     public virtual bool CanGoBack

  40:     {

  41:         get { return this.RootFrame.CanGoBack; }

  42:     }

  43:     

  44:     public virtual bool CanGoForward

  45:     {

  46:         get { return this.RootFrame.CanGoForward; }

  47:     }

  48:     

  49:     public virtual void Save()

  50:     {

  51:         throw new NotImplementedException();

  52:     }

  53:     

  54:     public virtual void Load()

  55:     {

  56:         throw new NotImplementedException();

  57:     } 

  58: }

   1: protected override void OnLaunched(LaunchActivatedEventArgs args)

   2: {

   3:     // get the instance from Injection Container

   4:     INavigationService ns = this.Container.Resolve<INavigationService>();

   5:  

   6:     if (args.PreviousExecutionState == ApplicationExecutionState.Terminated)

   7:     {

   8:         // load state if app was terminated

   9:         ns.Load();

  10:     }

  11:     

  12:     // initialize current window

  13:     ns.Initialize(Window.Current);

  14:  

  15:     // navigate to the first page

  16:     ns.Navigate(Pages.MainPageType);

  17: }

  18:  

  19: private void OnSuspending(object sender, SuspendingEventArgs e)

  20: {

  21:     // get the instance from Injection Container

  22:     INavigationService ns = this.Container.Resolve<INavigationService>();

  23:  

  24:     // save navigation status

  25:     ns.Save();

  26: }