Modern UI WPF - Manual Page Navigation (from ViewModel or View\Control\code-behind)

I have an MVVM application that I'm trying to move over to Modern UI, but I can't seem to figure out the Navigation Service...

Basically, my ViewModel is an ObservableCollection with an "AddItem" method, as an ICommand. When this method is executed, I want to switch back to the first MUI Group's 1st Link\Page, here is an Example snippet of Modern UI WPF...

<mui:ModernWindow ...>
    <mui:ModernWindow.MenuLinkGroups>
        <mui:LinkGroup DisplayName="Open Work">
            <mui:LinkGroup.Links>
                <mui:Link DisplayName="Current Activity" Source="/Pages/ActivityPage.xaml" />
                <mui:Link DisplayName="Activity Queue" Source="/Pages/Queue.xaml" />
            </mui:LinkGroup.Links>
        </mui:LinkGroup>
        <mui:LinkGroup DisplayName="Search" >
            <mui:LinkGroup.Links>
                <mui:Link DisplayName="Customers" Source="/Pages/SearchPage.xaml" />
            </mui:LinkGroup.Links>
        </mui:LinkGroup>
    </mui:ModernWindow.MenuLinkGroups>

So basically, from "SearchPage.xaml", the ICommand "AddItem" is executed, and I want to immediately switch back to "ActivityPage.xaml" (in the "Open Work" group).

Ideally, I'd like to do this from the ViewModel, but I don't mind attaching a Handler to the CollectionChanged event, and manually setting the Page, but the NavigationService samples (here) haven't helped me figure this one out...

As a last resort, I added MVVM Light from Nuget and I tried implementing IModernNavigationService in my ViewModel, but I can't figure out how to get the ViewModelLocator to work.

Found the answer. Much simpler than I thought it would be. In my ModernWindow code-behind, I add the following handler to the CollectionChanged event:

    private void Items_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
    {
        if(e.NewItems.Count > 0)
        {
            try
            {
                ContentSource = MenuLinkGroups.First().Links.First().Source;
            }
            catch (Exception error)
            {
                ModernDialog.ShowMessage(error.Message, FirstFloor.ModernUI.Resources.NavigationFailed, MessageBoxButton.OK);
            }
        }
    }