Handle navigation events

MUI includes a content navigation framework that handles content loading, unloading and history navigation based on link uris. If you want your content to be aware of navigation events such as loaded and unloaded events, you'll need to implement an interface.

Make your content navigation aware by implementing the IContent interface available in the FirstFloor.ModernUI.Windows namespace. The interface defines 4 methods:

public interface IContent
{
  void OnFragmentNavigation(FragmentNavigationEventArgs e);
  void OnNavigatedFrom(NavigationEventArgs e);
  void OnNavigatedTo(NavigationEventArgs e);
  void OnNavigatingFrom(NavigatingCancelEventArgs e);
}

Loading and unloading

The OnNavigatedTo method is invoked when the content becomes the active content in a frame. This is a good time to initialize your content.

The OnNavigatingFrom method is invoked when the content is about to become inactive. You can use the OnNavigatingFrom method to cancel navigation by setting the NavigatingCancelEventArgs.Cancel to true. The method OnNavigatedFrom is called when the content is no longer the active content.

Important: do not rely on WPF Loaded and Unloaded events for content initialization and clean up. The Loaded and Unloaded events are raised multiple times when the active content changes. This is due to the use of multiple ContentPresenters in the TransitioningContentControl required for fluent animations. Use OnNavigatedTo and OnNavigatedFrom instead.

Fragment navigation

The OnFragmentNavigation is called when navigation to a content fragment begins. Fragment navigation happens when you navigate to a link uri containing a fragment (use the # character).

Once IContent is implemented by your content pages, the navigation methods are automatically invoked when a page is loaded in a ModernFrame instance. The following code demonstrates a content sample that prevents navigation when the user doesn't allow it:

public class MyContent : UserControl, IContent
{
  public void OnFragmentNavigation(FragmentNavigationEventArgs e)
  {
  }
  public void OnNavigatedFrom(NavigationEventArgs e)
  {
  }
  public void OnNavigatedTo(NavigationEventArgs e)
  {
  }
  public void OnNavigatingFrom(NavigatingCancelEventArgs e)
  {
    // ask user if navigating away is ok
    if (ModernDialog.ShowMessage("Navigate away?", "navigate", MessageBoxButton.YesNo) == MessageBoxResult.No) {
      e.Cancel = true;
    }
  }
}