Question

I´ve already done some research on that problem, but I can´t find a workaround.

Here´s the problem:

I have an observableCollection of my custom class ListedNote. At first the ListBox displays the data, but there are some datas which are loaded async and won´t be updated. (e.g. a user picture)

<ScrollViewer VerticalScrollBarVisibility="Auto">
        <ListBox ItemsSource="{Binding Notes, UpdateSourceTrigger=PropertyChanged}" x:Name="Content" ItemTemplate="{StaticResource ListBoxCardFBLikeTemplate}"
                 HorizontalContentAlignment="Stretch">

        </ListBox>
    </ScrollViewer>

The ViewModel

....
private ObservableCollection<ListedNote> notes;

public ObservableCollection<ListedNote> Notes
        {
            get { return notes; }
            set { notes = value; RaisePropertyChanged(() => this.Notes); }
        }
private void LoadAttachmentsAsync(ListedNote note)
        {
            Async.Call(() => this.ServiceConnector.RetrieveAnnouncementAttachment(note.IdValue),
                mm =>
                {
                    if (mm != null)
                    {
                        if (mm.MultimediaType.IsPicture)
                            note.AttachedPicture = mm;
                        else
                            note.AttachedFile = mm;

                        note.AttachmentData = new List<byte>(mm.Data);

                        var index = this.Notes.IndexOf(note);
                        if (index >= 0)
                            this.Notes[index] = note;


                    }
                });
        }

Any idea?

Answer 1

ObservableCollection will only notify the UI when the collection’s contents have changed: that is, when a ListedNote is added or removed. It won’t notify the UI if the properties of a ListedNote already in the collection change.

Your ListedNote class needs to implement the INotifyPropertyChanged interface, in order for the UI to know that a property has changed on an individial note.