Bindings seems broken while using observable collection

Question

I have a ViewModel with an Observable Collection Property

 public ObservableCollection<GeographicArea> CurrentSensorAreasList
 {
     get
     {
        return currentSensorAreasList;
     }
     set
     {
        if (currentSensorAreasList != value)
        {
            currentSensorAreasList = value;
            OnPropertyChanged(PROPERTY_NAME_CURRENT_SENSOR_AREAS_LIST);
         }
      }
  }

Then in my xaml i have a binding

ItemsSource="{Binding CurrentSensorAreasList}">

This Observable Collection is updated trought a method that can be call in the viewModel constructor or when a collectionchanged handler from another list gets called.

I just clear the list and then add a fewer new items. While debugging i see all my new items updated on the list. But the UI does not get updated. When i regenerate the viewModel and then this update method gets call in the constructor the list gets updated in the UI.

Any ideas?? I don't know if the problem comes when i call the method from a handler.....

UPDATE #1

As requested i'm going the code when I update the list I have tested two ways to do this update

    private void UpdateList1()
        {
            if (globalAreaManagerList != null && OperationEntity != null) 
            {

              CurrentSensorAreasList.Clear();                         
              CurrentSensorAreasList.AddRange(globalAreaManagerList.Where(x => x != (OperationEntity as AreaManager)).SelectMany(areaRenderer => areaRenderer.AreaList));

//AddRange is an extension method.

            }
        }
private void UpdateList2()
        {
            if (globalAreaManagerList != null && OperationEntity != null) 
            {
                CurrentSensorAreasList = new ObservableCollection<GeographicArea>(globalAreaManagerList.Where(x => x != (OperationEntity as AreaManager)).SelectMany(areaRenderer => areaRenderer.AreaList))


            }
        }

Both cases works when i call it from the constructor. Then I have Other Lists where the Areas changes, and i get notified via CollectionChanged Handlers.

private void globalAreaManagerList_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
        {

            if (e.NewItems != null)
            {
                foreach (AreaManager newItem in e.NewItems)
                {
                    newItem.AreaList.CollectionChanged += AreaList_CollectionChanged;
                }
            }
            if (e.OldItems != null)
            {
                foreach (AreaManager oldItem in e.OldItems)
                {
                    oldItem.AreaList.CollectionChanged -= AreaList_CollectionChanged;
                }
            }
            UpdateList();
        }
        private void AreaList_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
        {
            UpdateList();
        }

So when i use UpdateList1 seems to work more times but suddenly the Binding is broken and then this update does not show in the UI.

That looks all ok. Please show the code where you are updating the collection. — Clemens
I put the code where i update the list. it seems strange because sometimes works and others not... — isra60

Maksym Ko Maksym Ko · Accepted Answer · 2015-07-16T17:10:55

If you wish change exactly an instance of collection I recomend using DependecyProperty for that case.

Here is:

    public ObservableCollection<GeographicArea> CurrentSensorAreasList
    {
        get { return (ObservableCollection<GeographicArea>)GetValue(CurrentSensorAreasListProperty); }
        set { SetValue(CurrentSensorAreasListProperty, value); }
    }

    public static readonly DependencyProperty CurrentSensorAreasListProperty =
        DependencyProperty.Register("CurrentSensorAreasList", typeof(ObservableCollection<GeographicArea>), typeof(ownerclass));

Where ownerclass - a name of class where you put this property.

But the better way is create only one instance of ObservaleCollection and then just change its items. I mean Add, Remove, and Clear methods.

Bindings seems broken while using observable collection

1 Answers