WPF Navigation Header MVVM

Question

I need tips from you guys, I hope someone can help me.

I want to make a WPF application which has a navigation header.

By navigation header I mean: I want to have a grid on top that contains buttons and when you click on the buttons, the bottom grid should show a completely different view. These views can also contain buttons and when clicking on these buttons only the lower grid should be updated and the top should remain as it is.

Also i want to use MVVM in my application.

below in the code you could better understand what I mean

`

<Window x:Class="WpfApp1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp1"
        mc:Ignorable="d"
        Title="MainWindow"
        Height="450"
        Width="800">

     <Grid>
          <Grid.RowDefinitions>
               <RowDefinition Height="Auto" />
               <RowDefinition Height="*" />
          </Grid.RowDefinitions>

          <Grid Grid.Row="0" Background="Red"> <!--this should be the header for the application-->
               
               <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="*"/>
                    <ColumnDefinition Width="*"/>
               </Grid.ColumnDefinitions>

               <Button Grid.Column="0" Content="View 1" Margin="4"/>
               <Button Grid.Column="1" Content="View 2" Margin="4"/>
               
          </Grid>

          <Grid Grid.Row="1" Background="LightBlue">
               <Label Content="View 1/ View 2 Content" FontSize="24" HorizontalAlignment="Center" VerticalAlignment="Center"/>
          </Grid>

     </Grid>

</Window>

`

enter image description here

Answer 1

Here is a begining: Encapsulate each view in a Grid and manage their visibility in the View Model. A simple solution if you are starting with MVVM.

THE MAIN VIEW

<Window x:Class="NavigationHeader.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:NavigationHeader"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Window.Resources>
        <BooleanToVisibilityConverter x:Key="BoolToVisConv" />
    </Window.Resources>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>

        <Grid Grid.Row="0" Background="Red">
            <!--this should be the header for the application-->

            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>

            <Button Grid.Column="0" Content="View 1" Margin="4" Command="{Binding View1Command}"/>
            <Button Grid.Column="1" Content="View 2" Margin="4" Command="{Binding View2Command}"/>

        </Grid>

        <Grid Grid.Row="1" Background="LightCoral" Visibility="{Binding View1Visibility, Converter={StaticResource BoolToVisConv}}">
            <StackPanel>
                <Label Content="View 1" FontSize="24" HorizontalAlignment="Center" VerticalAlignment="Center"/>
                <TextBox Text="my content" Width="100" Margin="10"/>
                <Button Content="Ok" Width="50" Margin="10"/>
            </StackPanel>
        </Grid>

        <Grid Grid.Row="1" Background="LightBlue" Visibility="{Binding View2Visibility, Converter={StaticResource BoolToVisConv}}">
            <Label Content="View 2" FontSize="24" HorizontalAlignment="Center" VerticalAlignment="Center"/>
        </Grid>

    </Grid>
</Window>

THE MAIN VM

For the View Model you need to install the Nuget's Package CommunityToolkit.Mvvm as the Main VM need these namespaces:

using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;

public class MainVM : ObservableObject
{
    private bool myView1Visibility;
    private bool myView2Visibility;

    public MainVM()
    { 
        myView1Visibility = false;
        myView2Visibility = false;
    }

    public bool View1Visibility
    {
        get { return myView1Visibility; }
        set
        {
            if (value == myView1Visibility) return;

            myView1Visibility = value;
            OnPropertyChanged(nameof(View1Visibility));
        }
    }

    public bool View2Visibility
    {
        get { return myView2Visibility; }
        set
        {
            if (value == myView2Visibility) return;

            myView2Visibility = value;
            OnPropertyChanged(nameof(View2Visibility));
        }
    }

    RelayCommand myView1Command;
    RelayCommand myView2Command;

    public RelayCommand View1Command
    {
        get
        {
            if (myView1Command == null)
                myView1Command = new RelayCommand(View1CommandAction);

            return myView1Command;
        }
    }

    public RelayCommand View2Command
    {
        get
        {
            if (myView2Command == null)
                myView2Command = new RelayCommand(View2CommandAction);

            return myView2Command;
        }
    }

    private void View1CommandAction()
    {
        View2Visibility = false;
        View1Visibility = true;
    }

    private void View2CommandAction()
    {
        View1Visibility = false;
        View2Visibility = true;
    }
}

Instanciate the VM in the Main's View code behind:

public partial class MainWindow : Window
{
    private readonly MainVM myMainVM;

    public MainWindow()
    {
        InitializeComponent();
        myMainVM = new MainVM();
        DataContext = myMainVM;
    }
}

Answer 2

In addition to what Yannick pointed out for the visibility converter, I would do the following.

Create two additional "UserControl" classes (similar xaml markup as your window, but have each user control draw just what IT is to represent. This way, if you need to move the stuff around, you fix that one control. It still resides within your outer main window. For example.

<Window x:Class="NavigationHeader.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:NavigationHeader"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Window.Resources>
        <BooleanToVisibilityConverter x:Key="BoolToVisConv" />
    </Window.Resources>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>

        <Grid Grid.Row="0" Background="Red">
            <!--this should be the header for the application-->

            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>

            <Button Grid.Column="0" Content="View 1" Margin="4" Command="{Binding View1Command}"/>
            <Button Grid.Column="1" Content="View 2" Margin="4" Command="{Binding View2Command}"/>

        </Grid>

        <local:MyFirstControl
           Grid.Row="1" 
           Background="LightCoral" 
           Visibility="{Binding View1Visibility, 
                         Converter={StaticResource BoolToVisConv}}"  />       

        <local:MySecondControl
           Grid.Row="1" 
           Background="LightBlue" 
           Visibility="{Binding View2Visibility, 
                         Converter={StaticResource BoolToVisConv}}" />

    </Grid>
</Window>


<UserControl x:Class="NavigationHeader.MyFirstControl"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:NavigationHeader"
        mc:Ignorable="d" >
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="50" />
            <RowDefinition Height="*" />
            <RowDefinition Height="*" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>
  
        <Label Grid.Row="0" Grid.Column="0"
            Content="View 1" FontSize="24" 
            HorizontalAlignment="Center" VerticalAlignment="Center"/>

         <TextBox Grid.Row="0" Grid.Column="1"
             Text="my content" Width="100" Margin="10"/>
         
         <Button Grid.Row="2" Grid.Column="2"
             Content="Ok" Width="50" />
    </Grid>
</UserControl>


<UserControl x:Class="NavigationHeader.MySecondControl"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:NavigationHeader" >
    <StackPanel>
        <Label Content="View 1" 
             FontSize="24" 
             HorizontalAlignment="Center" VerticalAlignment="Center"/>
        
        <TextBox Text="my content" Width="100" Margin="10"/>
        
        <Button Content="Ok" Width="50" Margin="10"/>
    </StackPanel>
</UserControl>

Notice the main window is referencing two more classes you would create as a user control MyFirstControl and MySecondControl . This can help keep your clutter in each respective control vs bloating the main control up and worrying about different formats such as one using a grid, and the other using a stack panel, docking panel, or whatever other type control you want to display.

Answer 3

I've used the community toolkit nuget package for the following. This implements inpc for me and generates some code using attributes.

The basic principle of what follows is called viewmodel first navigation. You should be able to find examples out there on the web explain more fully if you like.

To navigate this switches out a viewmodel instance which is then datatemplated into the view, with the viewmodel as datacontext.

Mainwindow

<Window.Resources>
    <DataTemplate DataType="{x:Type local:AlphaViewModel}">
        <local:AlphaView/>
    </DataTemplate>
    <DataTemplate DataType="{x:Type local:BetaViewModel}">
        <local:BetaView/>
    </DataTemplate>
    <DataTemplate DataType="{x:Type local:GammaViewModel}">
        <local:GammaView/>
    </DataTemplate>
</Window.Resources>
<Window.DataContext>
    <local:MainWindowViewModel/>
</Window.DataContext>
<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto" />
        <RowDefinition Height="*" />
    </Grid.RowDefinitions>

    <Grid Grid.Row="0" Background="Red">
        <!--this should be the header for the application-->

        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>

        <Button Command="{Binding NavigateViewModelCommand}"
                CommandParameter="{x:Type local:AlphaViewModel}"
                Content="Alpha" Grid.Column="0"  Margin="4"/>
        <Button Command="{Binding NavigateViewModelCommand}"
                CommandParameter="{x:Type local:BetaViewModel}"
                Content="Beta" Grid.Column="1"  Margin="4"/>

    </Grid>

    <Grid Grid.Row="1" Background="LightBlue">
        <ContentPresenter Content="{Binding CurrentViewModel}"/>
    </Grid>
</Grid>

Notice how viewmodel types are associated with usercontrols. Where an alphaviewmodel is presented to the view, it will be datatemplates with an alphaview.

Buttons bind to a command and pass a type as a parameter.

The contentpresenter is where that viewmodel will be presented to the view. That's bound to CurrentViewModel.

MainWindowViewModel

using CommunityToolkit.Mvvm.Input;

namespace WpfVMFirst
{
public partial class MainWindowViewModel : ObservableObject
{
    [ObservableProperty]
    private object? currentViewModel = new GammaViewModel();

    [RelayCommand]
    private void NavigateViewModel(Type type)
    {
        var vm = Activator.CreateInstance(type);
        CurrentViewModel = null;
        CurrentViewModel = vm;
    }
}
}

NavigateViewModel will become that NavigateViewModelCommand due to code generation. It takes the type I mentioned above and is going to generically instantiate a viewmodel from that. If you wanted to retain state between navigations, you could cache in a dictionary and re-use a viewmodel if it was already there.

Seting the currentviewmodel to null forces re templating. If you navigate to the same viewmodel it will force a new instance of the view usercontrol.

One of my usercontrols has a button of it's own:

Beta:

<Grid Background="Blue">
        <TextBlock Text="Beta"/>
    <Button HorizontalAlignment="Right"
            Content="Gamma"
            VerticalAlignment="Top"
            Command="{Binding DataContext.NavigateViewModelCommand, RelativeSource={RelativeSource AncestorType=Window}}"
            CommandParameter="{x:Type local:GammaViewModel}"/>
</Grid>
</UserControl>

Click that button and the view is navigated to gamma. That command works because it's using relativesource to look up the visual tree to the window, then use the command out the window's datacontext

Other viewmodels and usercontrols are pretty minimal. I have nothing in the alpha, beta and gamma viewmodels since this is just for demo purposes.

AlphaView

<Grid Background="Red">
    <TextBlock Text="Alpha"/>
</Grid>

That wiring up connecting viewmodel to view type can be put into a resource dictionary merged in app.xaml. In "real" apps the viewmodels are likely to have all sorts of functionality in them and it's usual to dependency inject those. The instantiation would be a bit more sophisticated.

As is reading any data such viewmodels require.

It's common to have an IGetData interface they implement with a GetData asynchronous task so they can be instantiated using a minimal CTOR and the data then retrieved using that abstracted method.

This is a mainstream commercial pattern which I've used and seen used successfully in real world single window apps.