WPF MVVM with multiple model instances

Question

There are lots of MVVM examples out there but I can't apply one to my case because I have several instances of the same classes . Also, I need to manipulate the models directly so I can subscribe some Observer's to their Observable's.

I've simplified my case for the question. I've three classes from my model : Lamp, Switch and Grid. They can interact thanks to an Observer/Observable mechanism. Basically, activating a switch switches on/off all the lamps connected to the same grid.

I want to make a window which shows a specific usage of these classes. There should Button's bound to Switch's and TextBlock's bound to Lamp's.

How can I bind each instance to the UI component I've prepared for it ?

Here is a simple case I'd like to build an UI for :

Grid entranceGrid = new Grid("Entrance Grid");
Lamp hallLamp = new Lamp("Hall Lamp");
Lamp stairsLamp = new Lamp("Stairs Lamp");
Switch downSwitch = new Switch("Downstair Switch");
Switch upSwitch = new Switch("Upstair Switch");

downSwitch.Subscribe(entranceGrid);
upSwitch.Subscribe(entranceGrid);
entranceGrid.Subscribe(hallLamp);
entranceGrid.Subscribe(stairsLamp);

// Below are four instances I'd like to bind to some UI component.
LampViewModel hallLampVM = new LampViewModel(hallLamp);
LampViewModel stairsLampVM = new LampViewModel(stairsLamp);
SwitchViewModel downSwitchVM = new downSwitchVM(downSwitch);
SwitchViewModel upSwitchVM = new downSwitchVM(upSwitch);

Here is my full code if you want to play with it (VS 2017)

Answer 1

This answer is ugly but it does work and maybe it will help someone to come with something better.

I will implement this solution for the time being. Maybe, I'll just work on something better to handle the NotifyPropertyChanged.

The window XAML :

<Window.DataContext>
    <vm:MainViewModel />
</Window.DataContext>
<Grid Margin="0,0,0,0">
    <Grid.RowDefinitions>
        <RowDefinition Height="2*" />
        <RowDefinition Height="3*" />
        <RowDefinition Height="2*" />
    </Grid.RowDefinitions>
    <GroupBox Grid.Row="0" Header="Entrée">
        <Grid>
            <Grid.RowDefinitions>
                <RowDefinition/>
                <RowDefinition/>
            </Grid.RowDefinitions>
            <Grid.ColumnDefinitions>
                <ColumnDefinition />
                <ColumnDefinition />
                <ColumnDefinition />
            </Grid.ColumnDefinitions>
            <TextBlock Grid.Row="0" Grid.Column="0" Text="Hall d'entrée"/>
            <TextBlock Grid.Row="1" Grid.Column="0" Text="Escalier"/>

            <TextBlock Grid.Row="0" Grid.Column="1" Text="{Binding TxtHallLamp}"/>
            <TextBlock Grid.Row="1" Grid.Column="1" Text="{Binding TxtStairsLamp}"/>

            <Button Grid.Row="0" Grid.Column="2" Content="rez" Command="{Binding DownSwitchCommand}"/>
            <Button Grid.Row="1" Grid.Column="2" Content="1er" Command="{Binding UpSwitchCommand}"/>
        </Grid>
    </GroupBox>
    [Few lines you don't need]
</Grid>

The ViewModelBase along the MainViewModel :

public class ViewModelBase : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    public void NotifyPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }

    public bool NotifyPropertyChanged<T>(ref T variable, T value, [CallerMemberName] string propertyName = null)
    {
        if (object.Equals(variable, value)) return false;

        variable = value;
        NotifyPropertyChanged(propertyName);
        return true;
    }
}


class MainViewModel : ViewModelBase
{
    private Lamp _HallLamp, _StairsLamp;
    private Switch _DownSwitch, _UpSwitch;

    private IRelayCommand _DownSwitchCommand, _UpSwitchCommand;

    public MainViewModel()
    {
        #region entrance

        Grid entranceGrid = new Grid("Entrance Grid");
        _HallLamp = new Lamp("Hall Lamp");
        _StairsLamp = new Lamp("Stairs Lamp");
        _DownSwitch = new Switch("Downstair Switch");
        _UpSwitch = new Switch("Upstair Switch");

        _DownSwitch.Subscribe(entranceGrid);
        _UpSwitch.Subscribe(entranceGrid);
        entranceGrid.Subscribe(_HallLamp);
        entranceGrid.Subscribe(_StairsLamp);

        #endregion // entrance
    }

    private string LampToTxt(Lamp lamp)
    {
        return lamp.Light ? "ON" : "OFF";
    }

    public string TxtHallLamp
    {
        get
        {
            return LampToTxt(_HallLamp);
        }
    }

    public string TxtStairsLamp
    {
        get
        {
            return LampToTxt(_StairsLamp);
        }
    }

    private void NotifyEntranceGridPropertyChanged()
    {
        NotifyPropertyChanged(nameof(TxtHallLamp));
        NotifyPropertyChanged(nameof(TxtStairsLamp));
    }

    public IRelayCommand DownSwitchCommand
    {
        get
        {
            return _DownSwitchCommand ?? (_DownSwitchCommand = new RelayCommand(
                () => {
                    _DownSwitch.Press();
                    NotifyEntranceGridPropertyChanged();
                },
                () => true));
        }
    }

    public IRelayCommand UpSwitchCommand
    {
        get
        {
            return _UpSwitchCommand ?? (_UpSwitchCommand = new RelayCommand(
                () => {
                    _UpSwitch.Press();
                    NotifyEntranceGridPropertyChanged();
                },
                () => true));
        }
    }
}

And the interface IRelayCommand along the class RelayCommand :

public interface IRelayCommand : ICommand
{
    void RaiseCanExecuteChanged();
}

class RelayCommand : IRelayCommand
{

    private Action _Execute;
    private Func<bool> _CanExecute;
    public event EventHandler CanExecuteChanged;

    public RelayCommand(Action Execute) : this(Execute, null)
    {

    }

    public RelayCommand(Action Execute, Func<bool> CanExecute)
    {
        if (Execute == null)
            throw new ArgumentNullException();

        _Execute = Execute;
        _CanExecute = CanExecute;
    }

    public bool CanExecute(object parameter)
    {
        return (_CanExecute == null) ? true : _CanExecute();
    }

    public void Execute(object parameter)
    {
        _Execute();
    }

    public void RaiseCanExecuteChanged()
    {
        if (CanExecuteChanged != null)
        {
            CanExecuteChanged(this, EventArgs.Empty);
        }
    }
}