UWP - Refreshing listview and CollectionViewSource - c

Question

I have created ChatMessageGroup and ChatMessageGroupCollection and a ListView with ItemsSource set to CollectionViewSource:
<ListView x:Name="ChatMessageLv" ItemsSource="{Binding SelectedChat.ChatMessageGroupCollection.Cvs.View}" ItemTemplateSelector="{StaticResource ChatMessageDataTemplateSelector}">
public class ChatMessageGroup : IGrouping<DateTime, ChatMessage>, INotifyCollectionChanged
{
private ObservableCollection<ChatMessage> _chatMessages;
public DateTime Key { get; set; }
public ObservableCollection<ChatMessage> ChatMessages
{
get { return _chatMessages; }
set
{
if (_chatMessages != null)
_chatMessages.CollectionChanged -= CollectionChanged;
_chatMessages = value;
_chatMessages.CollectionChanged += CollectionChanged;
}
}
public ChatMessageGroup()
{
ChatMessages = new ObservableCollection<ChatMessage>();
}
public IEnumerator<ChatMessage> GetEnumerator()
{
return ChatMessages.GetEnumerator();
}
IEnumerator IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
public event NotifyCollectionChangedEventHandler CollectionChanged;
}
public class ChatMessageGroupCollection : IEnumerable<ChatMessageGroup>
{
private readonly ObservableCollection<ChatMessageGroup> _groups;
public ObservableCollection<ChatMessage> Source { get; set; }
public CollectionViewSource Cvs { get; set; }
public ChatMessageGroupCollection(ObservableCollection<ChatMessage> messages)
{
Source = messages;
messages.CollectionChanged += Messages_CollectionChanged;
var groups = messages
.GroupBy(GetGroupKey)
.Select(x => new ChatMessageGroup()
{
Key = x.Key,
ChatMessages = x.OrderBy(GetGroupKey).ToObservableOrDefault()
})
.OrderBy(x => x.Key);
_groups = new ObservableCollection<ChatMessageGroup>(groups);
Cvs = new CollectionViewSource() { IsSourceGrouped = true, Source = _groups };
}
...
Everything works fine in here except the changes inside group collection:
_groups.Add(new ChatMessageGroup()); -> this line reflect changes in ListView
but if I do like this: _groups[0].ChatMessages.Add(new ChatMessage()) it doesn't work even though ChatMessageGroup is implementing INotifyCollectionChanged and is raised every time ChatMessages ObservableCollection is changed.
The workaround is to update ChatMessages and remove group from _groups and then add it again but it's not a solution. Refresh() on CollectionViewSource is not available in UWP. Are there any other solutions?

Answer 1

Whilst this doesn't technically qualify as an answer to the question I do think it might qualify as an architectural answer.
The way to make a grouped list view update based on the underlying collection changing in WPF is as simple as setting IsLiveGroupingRequested to true on the CollectionViewSource instance declared in XAML.
As I've been working my way through UWP (after nearly a decade of WPF) I've come to the conclusion that Microsoft are suggesting through omission that this isn't the right approach to the problem for UWP. So going to the lengths of implementing the feature yourself could be construed as missing the point somewhat.
In my particular situation I've decided to change my approach entirely and implement the rendering as multiple instance of ListViews as opposed to forcing an old paradigm onto a new platform.
The result of this actually made me arrive at a solution that improved my UX to boot.
Food for thought ...