WPF

public HomeViewModel(MainWindowViewModel mwvm)
{
    TaskList = new ObservableCollection<Models.Task>(tDC.Tasks);
    MwVm = mwvm;
}

public MainWindowViewModel MwVm
{
    get { return _mwVm; }
    set {if(value != null)
            _mwVm = value;
            RaisePropertyChanged();
            ViewChange();
    }
}

<ListView x:Name="LstVviewTaskList" Height="181" Width="120" Margin="10,35,270,0" VerticalAlignment="Top" VerticalContentAlignment="Top" HorizontalContentAlignment="Left" ItemsSource="{Binding TaskList}" SelectedItem="{Binding SelectedTask,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}">
           <ListView.ContextMenu>
               <ContextMenu>
                   <MenuItem Header="Add Task" Background="AliceBlue" Command="{Binding MwVm, UpdateSourceTrigger=PropertyChanged}"/>
                   <MenuItem Header="Edit Task" Background="AliceBlue" Command="{Binding MwVm, UpdateSourceTrigger=PropertyChanged}"/>
                   <MenuItem Header="Remove Task" Background="AliceBlue" Command="{Binding MwVm, UpdateSourceTrigger=PropertyChanged}"/>
               </ContextMenu>
           </ListView.ContextMenu>

MainWindowViewModel.ctor 
⇒ HomeViewModel.ctor 
⇒ HomeViewModel.MwVm.set 
⇒ HomeViewModel.ViewChange 
⇒ MainWindowViewModel.DisplayAddEditView

public static class AppCore
{
    public static UserEntity CurrentUser { get; private set; }
    
    public static event EventHandler CurrentUserChanged;
    
    /*
    Or:
    public static event EventHandler<PropertyChangedEventArgs> StaticPropertyChanged;
    */
 
    public static void Login()
    {
       // ... log in the user and set CurrentUser 
       
       CurrentUserChanged?.Invoke(null, EventArgs.Empty);
       
       /*
       Or:
       var handler = StaticPropertyChanged;
       if (handler != null) handler(null, new PropertyChangedEventArgs(nameof(CurrentUser)));
       */
    }
}

What's New in WPF Version 4.5 - Binding to static properties[^]:

The data binding engine recognizes when the property's value changes if a static event is raised.

<TextBlock Text="{Binding Source={x:Static local:AppCore.CurrentUser}, Path=FullName, Mode=TwoWay}"/>

public static class AppCore
{
    public static event EventHandler CurrentUserChanged;

    public static UserEntity CurrentUser { get; private set; }

    public static bool Login(CredentialEntity credentials)
    {
        var loggedIn = false;

        LoginResponse response = _appSecurity.Login(credentials);

        if (response.Result == Result.Success)
        {
            CurrentUser = response.User;
            CurrentUserChanged?.Invoke(null, EventArgs.Empty);
            loggedIn = true;
        }

        return loggedIn;
    }

}

<TextBlock Text="{Binding Path=(local:AppCore.CurrentUser.FullName), Mode=TwoWay}"/>

WPF 4.5 – Part 9 : binding to static properties UPDATED | Jonathan ANTOINE's thoughts on Windows development[^]:

It does not work with the x:Static extension

<TextBlock DataContext="{Binding Path=(local:AppCore.CurrentUser)}" Text="{Binding Path=FullName, Mode=TwoWay}"/>

public static class AppCore
{
    public static event EventHandler<PropertyChangedEventArgs> StaticPropertyChanged;

    public static UserEntity CurrentUser { get; private set; }

    private static string _FullName;
    public static string FullName
    {
        get { return _FullName; }
        set
        {
            if (_FullName != value)
            {
                _FullName = value;
                NotifyStaticPropertyChanged("FullName");
            }
        }
    }

    private static void NotifyStaticPropertyChanged(string propertyName)
    {
        if (StaticPropertyChanged != null)
            StaticPropertyChanged(null, new PropertyChangedEventArgs(propertyName));
    }

    public static bool Login(CredentialEntity credentials)
    {
        var loggedIn = false;

        LoginResponse response = _appSecurity.Login(credentials);

        if (response.Result == Result.Success)
        {
            CurrentUser = response.User;
            FullName = response.User.FullName;
            loggedIn = true;
        }

        return loggedIn;
    }
}

Kevin Marois wrote:

What's the best way to make a Chess board using WPF and MVVM?

Kevin Marois wrote:

BoardSquare square = board.Children.Cast<BoardSquare>().First(e => Grid.GetRow(e) == 0 && Grid.GetColumn(e) == 0);
square.Piece = new RookBlack();
 
square = board.Children.Cast<BoardSquare>().First(e => Grid.GetRow(e) == 0 && Grid.GetColumn(e) == 1);
square.Piece = new BishopBlack();