Page.NavigationService Property

Pages can be hosted by multiple types of hosts, including Window, NavigationWindow, Frame, and a browser.

Pages often need to integrate with their host's navigation to provide in-page navigation support. However, because a page may not know what its host will be at run time, it cannot integrate directly with its host's navigation members to do so.

Instead, it can attempt to use a navigation service, which is a service that supports browser-style navigation and is encapsulated by the NavigationService class. You cannot create your own NavigationService instance, though. Instead, host types such as NavigationWindow, Frame, or a browser create their own NavigationService instance that you can access from the NavigationService property.

The navigation service that is returned from the NavigationService property is the instance of the NavigationService class that is managed by the first navigator up the visual tree. If one is not found, Nothing is returned, indicating a page's host does not support navigation.

Note
The Window class does not support navigation and does not provide a navigation service.

The following example shows how a page can check if a navigation service is available and, if so, use it to navigate back to the previous page.

Partial Public Class HomePage
    Inherits Page
    Public Sub New()
        InitializeComponent()

        ' Don't allow back navigation if no navigation service
        If Me.NavigationService IsNot Nothing Then
            Me.goBackButton.IsEnabled = False
        End If
    End Sub

    Private Sub goBackButton_Click(ByVal sender As Object, ByVal e As RoutedEventArgs)
        ' Go to previous entry in journal back stack
        If Me.NavigationService.CanGoBack Then
            Me.NavigationService.GoBack()
        End If
    End Sub
End Class

.NET Framework

.NET Framework Client Profile

Windows 8 Consumer Preview, Windows Server 8 Beta, Windows 7, Windows Server 2008 SP2, Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

Reference