wpf-like trigger in code behind

Question

I'm writing a simple game in c# using wpf. In my xaml.cs I create a Game object that does all the work.

I need to be able to reload the window on a certain propertyChange in the Game object. I already have this in my xaml:

<TextBlock x:Name="PhaseTB" Text="{Binding Phase, UpdateSourceTrigger=PropertyChanged}" HorizontalAlignment="Center"/>

and Phase is part of the Game object:

public class Game : INotifyPropertyChanged
{
    private static Game _instance;
    private GamePhase phase;

    public static Game Instance
    {
        get
        {
            if (_instance == null)
                _instance = new Game(10, 10);
            return _instance;
        }
    }
 public GamePhase Phase
 {
     get { return phase; }
     set 
     { 
         phase = value;
         OnPropertyChanged("Phase");
     }
 }

public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string propertyName)
{
    if (PropertyChanged != null)
    {
        PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}

That all works fine and the textbox is updated according to the Phase value.

My question is: How do I call on a method whenever the Phase value changes? The text changes just fine, but I have no idea how to call a code-behind method.

(sorry for noob-question. I have inherited the code and don't really understand how the whole thing works)

Answer 1

You need to subscribe to the event PropertyChanged :

`<yourDataContext>`.PropertyChanged += propertyChangedHandler;

where <yourDataContext> is your DataContext and propertyChangedHandler is the event handler.

Note - You can access the Data Context like this:

((Game)textBox1.DataContext).PropertyChanged += propertyChangedHandler;

or

((Game)this.DataContext).PropertyChanged += propertyChangedHandler;

if your TextBox inherits the DataContext from the Window/Page's main class.

That event exists precisely for the very purpose you mentioned.

And as for where this code should be put, I would generally put it in the constructor since it's assigning event handlers:

public class MainWindow() {
    public MainWindow() {
        InitializeComponent();
        // Here go the event handlers....
    }
}

More info:

• Property Changed Event
• Data Context