Binding Start/Stop text on Stopwatch.IsRunning - Property Changed

Question

I have something like this in xaml:

<Button Content="{Binding MyStopwatch.IsRunning,
        Converter={StaticResource BoolToStr}}"/>

I need to display Start, when IsRunning is false and Stop, when IsRunning is true. I have no problem with converter or binding itself.

I have problem with refreshing IsRunning property. When IsRunning property change while programm is running - it does not change Start/Stop text.

I know how to implement INotifyPropertyChange on my own properties. But I dont know how to implement (something like) property change on IsRunning

Answer 1

If you want to update your bindings, you can call the PropertyChanged on property MyStopwatch whenever you start or stop a stopwatch.

OnPropertyChanged("MyStopwatch");

Answer 2

You can't make StopWatch implement INotifyPropertyChanged. What you can do, is create your own wrapper for it, and use that instead. For example:

public class StopwatchWrapper : INotifyPropertyChanged
{
    Stopwatch _stopwatch;

    private bool _isRunning;
    public bool IsRunning
    {
        get { return _isRunning; }
        set
        {
            if (_isRunning != value)
            {
                _isRunning = value;
                OnPropertyChanged("IsRunning");
            }
        }
    }

    public StopwatchWrapper()
    {
        _stopwatch = new Stopwatch();
        _isRunning = false;
    }

    public void Start()
    {
        _stopwatch.Start();
        IsRunning = _stopwatch.IsRunning;
    }

    public void Stop() 
    {
        _stopwatch.Stop();
        IsRunning = _stopwatch.IsRunning;
    }

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