CODEWITHSUNDEEP
c#wpfbindingdispatchertimer
omarmallat
omarmallat

Reputation: 734

Binding to property not working with DispatcherTimer

I have some TextBlock bound to a property with DependencyProperty. When a DispatcherTimer changes this property, the TextBlock does not update. Even in debugging, I can see that the property get updated, but TextBlock remains unchanged.

Details: I have a class:

    public class myTimer
{
    public System.DateTime Duration { get; set; }
    public System.DateTime Elapsed { get; set; }
    public System.TimeSpan Remaining {
        get {
            return Duration.Subtract(new DateTime(Duration.Year, Duration.Month, Duration.Day, Elapsed.Hour, Elapsed.Minute, Elapsed.Second));
        }
    }
}

I have in my xaml code behind a DependencyProperty of type myTimer

    public static DependencyProperty currentTimerProperty = DependencyProperty.Register("CurrentTimer", typeof(myTimer),  typeof(Question));
    public myTimer CurrentTimer
    {
        get { return (myTimer)GetValue(currentTimerProperty); }
        set { SetValue(currentTimerProperty, value); }
    }

and I have three TextBlock bounded to this property:

    <TextBlock  Style="{StaticResource myTimer}">
         <TextBlock.Text>
               <MultiBinding StringFormat="{}{0:00}:{1:00;00}">
                      <Binding ElementName="Questionctl" Path="CurrentTimer.Remaining.Minutes"/>
                      <Binding ElementName="Questionctl" Path="CurrentTimer.Remaining.Seconds"/>
                </MultiBinding> 
           </TextBlock.Text>
     </TextBlock>
     <TextBlock Text="{Binding ElementName=Questionctl,Path=CurrentTimer.Duration,StringFormat=HH:mm:ss}"/>
     <TextBlock Text="{Binding ElementName=Questionctl,Path=CurrentTimer.Elapsed,StringFormat=HH:mm:ss}"/>

the timer is initialized like this:

dispatcherTimer = new System.Windows.Threading.DispatcherTimer();
dispatcherTimer.Tick += new EventHandler(dispatcherTimer_Tick);
dispatcherTimer.Interval = new TimeSpan( 0 , 0, 1);
dispatcherTimer.Start();

so simply, every second, it will add 1 second to the property Elapsed:

CurrentTimer.Elapsed = CurrentTimer.Elapsed.AddSeconds(1);

Upvotes: 1

Views: 772

Answers (2)

dave
dave

Reputation: 185

If that is your actual problem and not a simplification, you'll have another issue.

Your code will only work if, and only if, the dispatch timer event happens exactly on one second intervals. That is not guaranteed by that api.

If you instead capture the system time when the timer fires it will calculate the correct times even if the time between event firing is sporadic.

Upvotes: 0

Henka Programmer
Henka Programmer

Reputation: 747

Update your Class definition of myTimer to implement INotifyPropertyChanged looks like:

public class myTimer : INotifyPropertyChanged
{
    private System.DateTime _duration;

    public System.DateTime Duration
    {
        get
        {
            return _duration;
        }
        set
        {
            _duration = value;
            RaisePropertyChanged("Duration");
            RaisePropertyChanged("Remaining");
        }
    }

    private DateTime _elapsed;

    public DateTime Elapsed
    {
        get { return _elapsed; }
        set
        {
            _elapsed = value;
            RaisePropertyChanged("Elapsed");
            RaisePropertyChanged("Remaining");
        }
    }

    public System.TimeSpan Remaining
    {
        get
        {
            return Duration.Subtract(new DateTime(Duration.Year, Duration.Month, Duration.Day, Elapsed.Hour, Elapsed.Minute, Elapsed.Second));
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

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

Upvotes: 2

Related Questions