Using RelativeTimeConverter and updating the Textblock's text as time goes by

Question

In my MainPage.xaml I have a ListBox, with a datatemplate like the following:

<DataTemplate>
<TextBlock Name="DateTextBlock"  Text="{Binding Modified,  Converter={StaticResource RelativeTimeConverter}}"/>           
</DataTemplate>

When the app is launched, the conversion is done once, and then until I relaunch the app, the textblock's text remains the same, even if I navigate to another page and return to MainPage.xaml .

All I want is to use the converter continually, and not only once when the Modified property changes, so as to show that time goes by, as the user is using my app. How could this be accomplished?

andrewpey · Accepted Answer · 2012-12-14T09:01:58.727

0

Do you use INotifyPropertyChanged? Please see this article explaining data binding pretty clear.

EDIT: According to new information from comments you have use INotifyPropertyChanged, but searching for solution to notify UI about property has changed on regular basis. So consider using some sort of timers, for example DispatcherTimer:

DispatcherTimer timer = new DispatcherTimer();
timer.Interval = TimeSpan.FromSeconds(4);
timer.Tick += delegate(object s, EventArgs args)
{
    foreach (YourItem item in ViewModel.Items)
    {
        item.NotifyPropertyChanged("Modified");
    };
}
timer.Start();

Also (of course) add this method to YourItem class:

public void NotifyPropertyChanged(string propertyName)  
{
    OnPropertyChanged(propertyName); 
}

edited Dec 14 '12 at 09:01

answered Dec 13 '12 at 12:19

andrewpey

650
3
11

I do use INotifyPropertyChanged but this is irrelevant to my problem. The "Modified" property does not change(its value is assigned once, by DateTime.Now()), but as time goes by, the relevant time label provided by the RelativeTimeConverter should change (e.g: a few minutes ago, about an hour ago, 24 hours ago etc.). This does not happen, except when I quit the app and re-launch it. So the question is like: "how can I force the Binding to refresh every, lets say, 4 seconds? – Icarus Dec 13 '12 at 16:04
Consider using [DispatcherTimer](http://msdn.microsoft.com/ru-ru/library/system.windows.threading.dispatchertimer(v=vs.95).aspx) to raise OnPropertyChanged event for Modified property. – andrewpey Dec 14 '12 at 08:38
I think your suggestion should work, but I cannot implement it since I have another problem, which I don't know how to resolve. I am using an ObservableCollection, but like this: MyClass<> obsList = new MyClass>(MyClass_args); If it was a simple ObservableCollection, the implementation of your suggestion would be straightforward to me. But in this case, I don't know how to do it, as there is no public GetEnumerator definition for MyClass<>. – Icarus Dec 14 '12 at 17:49
Why not to implement property to expose `T` (`ObservableCollection` is this case) and enumerate it? – andrewpey Dec 15 '12 at 00:04

Using RelativeTimeConverter and updating the Textblock's text as time goes by

1 Answers1