WPF: Composite Application with Page Navigation

Question

I am currently writing an application to which the composite methodology fits like a glove.... almost!

I also need a way to navigate between views, including maintaining a journal for navigation backward and forward.

What is the best way to combine these two methodologies, on one hand the single Window based CAG shell with its UserControl derived views, and on the other hand the convenient NavigationWindow shell with its Page derived views and journal?

Thanks!

Answer 1

You can display anything in a NavigationWindow, not just Pages. A simple way to make it work is to define in the NavigationWindow's resources a DataTemplate for each ViewModel you want to display. Bind the Content property of the NavigationWindow to a property of your main ViewModel, and you're done : changing that property will update the NavigationWindow content, and the appropriate DataTemplate will be picked automatically

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UPDATE

I just looked at the code of a project of mine where I used a NavigationWindow. Actually I was mistaken, it doesn't work by binding the Content (or maybe it works, but that's not what I did). Instead I created a INavigationService interface, implemented by my App class, which handles the navigation by calling the NavigationWindow.Navigate method. That way, the navigation history is maintained by the NavigationWindow.

Here's an extract from my project

MainWindow.xaml :

<NavigationWindow x:Class="MyApp.MainWindow"
                  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                  xmlns:vm="clr-namespace:MyApp.ViewModel"
                  xmlns:view="clr-namespace:MyApp.View"
                  Title="{Binding Content.DisplayName, RelativeSource={RelativeSource Self}, FallbackValue=The Title}"
                  Height="600" Width="800">
    <NavigationWindow.Resources>
        <DataTemplate DataType="{x:Type vm:HomeViewModel}">
            <view:HomeView />
        </DataTemplate>
        <DataTemplate DataType="{x:Type vm:CustomerViewModel}">
            <view:CustomerView />
        </DataTemplate>
    </NavigationWindow.Resources>
</NavigationWindow>

App.xaml.cs :

    ...

    private void Application_Startup(object sender, StartupEventArgs e)
    {
        LoadConfig();

        MyApp.MainWindow window = new MainWindow();
        INavigationService navigationService = this;
        HomeViewModel viewModel = new HomeViewModel(navigationService);
        this.MainWindow = window;
        window.Navigate(viewModel);
        window.Show();
    }

When I need to navigate to another view, I just call the Navigate method with the ViewModel as a parameter, and WPF automatically picks the appropriate DataTemplate from the resources.