Populating ObservableCollection for CollectionView using MainThread in .NET MAUI app

I thought I understood when to use the MainThread in a .NET MAUI app but maybe not fully so I’d appreciate some pointers on this. In one particular page, I’m getting the following error message:

Objective-C exception thrown. Name: NSInternalInconsistencyException
Reason: Modifications to the layout engine must not be performed from
a background thread after it has been accessed from the main thread.

In my page, I have a CollectionView:

<CollectionView
   ItemsSource="{Binding Feed}"
   RemainingItemsThreshold="0"
   RemainingItemsThresholdReachedCommand="{Binding GetMoreFeedItemsCommand}"
   IsVisible="{Binding IsFeedVisible}">
   ... Omitted for brevity
<CollectionView>

And here’s my view model code:

private int LastFeedId { get; set; }
private DateTime LastDataFetchTimeStamp { get; set; }

public ObservableCollection<FeedItem> Feed { get; } = new();

[RelayCommand]
async Task GetMoreFeedItems()
{
   if(LastDataFetchTimeStamp.AddSeconds(30) >= DateTime.UtcNow)
      return;

   IsBusy = true;

   // Fetch new data
   await GetFeedDataAsync();

   IsBusy = false;
}

private async Task GetFeedDataAsync()
{
   var data = await MyService.GetFeedDataAsync(LastFeedId);

   LastDataFetchTimeStamp = DateTime.UtcNow;

   if(data != null && data.Count > 0)
   {
      LastFeedId = data.Max(x => Id);
      foreach(var item in data)
         Feed.Add(item);
   }

   IsFeedVisible = true;
}

internal async Task InitAsync()
{
   // InitAsync() gets called OnAppearing()
   if(LastDataFetchTimeStamp.AddSeconds(30) < DateTime.UtcNow)
      await GetFeedDataAsync();
}

The part that I want to understand is that when I call an async function, it gets handled in a background thread. So calling GetFeedDataAsync() method should be handled by a background thread.

With that said, I need to populate my ObservableCollection<FeedItem> which provides the data to the CollectionView.

Do I need to handle the foreach loop that adds data to the ObservableCollection in MainThread like:

...
MainThread.BeginInvokeOnMainThread(() =>
{
   foreach(var item in data)
      Feed.Add(item);
});
...

In other pages with a similar situation, I actually add data to an ObservableCollection without invoking the MainThread and I get no errors.

However on this page, I am getting the error mentioned above. I wonder if that’s because the GetFeedDataAsync() gets called both in the very beginning when the page appears and also to fetch more items after the user reaches the bottom of his feed.

The interesting verbiage in the error message is:

… after it has been accessed from the main thread

I’m trying to understand why I don’t get errors on other pages where the data fetch method gets called only once as opposed to this page that produces this error.

Should I always use MainThread for my foreach loops that add to data to ObservableCollections that provide data to CollectionViews?