Lists and search

AddRange and ReplaceRange raise one CollectionChanged Reset. Do not Add in a loop for mid or large lists (MVVME011). Large lists must also virtualize in CollectionView. After a page is visible, prefer Add / Insert over ReplaceRange on Android BindableLayout — SnapshotCollection + BindableLayout is MVVME012. CollectionBind.AsyncFetch is the RemainingItemsThreshold path when the fetch is async.

var items = new ObservableRangeCollection<Product>();
items.AddRange(page);
items.ReplaceRange(next);

PagedCollection<T> / DelegatePagedCollection<T> own load-more, refresh, and retry — not a live chat inbox. SnapshotCollection<T> loads once in InitializeAsync; later LoadAsync calls are no-ops unless force is true. After appear, mutate with AddLocal / Insert. CollectionBind.AsyncFetch is the blessed RemainingItemsThreshold path when the fetch is async. Do not pair DelegatePagedCollection with CollectionView RemainingItemsThreshold when the fetch is sync (MVVME013). SearchQuery.Text binds to Entry or MvvmSearch; filter from CommittedText after debounce. Android SearchBar is not required.

public sealed class InboxViewModel : ViewModel
{
    public SnapshotCollection<Conversation> Inbox { get; }
    public SearchQuery Search { get; } = new();

    public InboxViewModel(IInbox catalog)
    {
        Inbox = new SnapshotCollection<Conversation>(
            ct => catalog.ListAsync(Search.CommittedText, ct));
    }

    protected override Task InitializeAsync(CancellationToken cancellationToken) =>
        Inbox.LoadAsync(cancellationToken: cancellationToken);
}

// catalog paging (not a live inbox)
await Products.RefreshAsync(ct);
await Products.LoadMoreAsync(ct);