Xamarin.Forms CollectionView Infinity Scroll freezed after sometime

Question

I made a scrolling app with CollectionView with ItemSource=Photos and after sometime scrolling the app got freezed. This is my ViewModel counstructor code with all elements:

        public MainPageViewModel()
        {
            CounterData = 20;
            StandartCounter = 20;
            LoadPhotosCommand = new Command(execute: async () => await ExecuteGetAllPhotos());
            LoadRefreshCommand = new Command(execute: async () => await ExecuteRefreshGetAllPhotos());
            LoadNewPhotosCommand = new Command(execute: async () => await ExecuteGetNewPhotos());
            LoadSelectedPhotoCommand = new Command(execute: async () => await ExecuteGetDetailsSelectedPhoto());
            Photos = new ObservableCollection<Photo>();
            PhotosAll = new ObservableCollection<Photo>();
            PhotosModel = new PhotosModel();
            SelectedPhoto = new Photo();
        }

This is my logic in the ViewModel, and this function get all photos from the API - store them in the PhotosAll list and add 20 elements to Photos list which is ItemSource of the collectionView:

        async Task ExecuteGetAllPhotos()
        {
            if (IsBusy)
                return;      
            try
            {
                IsBusy = true;
                Photos.Clear();
                PhotosAll.Clear();
                PhotosModel = await InstagramCloneDataStore.GetAllPhotos();
                if (PhotosModel != null)
                {
                    foreach (var photo in PhotosModel.Photos)
                    {

                        PhotosAll.Add(photo);
                    }

                    foreach (var el in PhotosAll.Skip(0).Take(StandartCounter))
                    {
                        Photos.Add(el);
                    }
                    CounterData = StandartCounter;
                }
            }
            catch (Exception ex)
            {
                Debug.WriteLine(ex);
                var msg = ex.Message;
            }
            finally
            {
                IsBusy = false;
            }
        }

This is the function from the RemainingItemsThresholdReachedCommand and the logic is when user reach scrolling 20 items read new 20 items and add them to Photos list.

         async Task ExecuteGetNewPhotos()
        {
            if (IsBusy)
                return;
            try
            {
                IsBusy = true;
                await Task.Delay(100);
                foreach (var el in PhotosAll.Skip(CounterData).Take(StandartCounter))
                {
                    Photos.Add(el);
                }
                CounterData += StandartCounter;
            }
            catch (Exception ex)
            {
                Debug.WriteLine(ex);
                var msg = ex.Message;
            }
            finally
            {
                IsBusy = false;
            }
        }

First started to scrolling verywell but after sometime the application got freezed. Does anyone have the same problem? Or have some solution for this?

UPDATE It looks like Photos list look bigger the loading new items getting slow

Answer 1

After hours of reviewing my code i learn 2 things:

1. RemainingItemsThreshold="{Binding CounterData}" -> CounteData is static value and can't be changed.
2. I implemented one value for skip or u can use CounterData or i use StandartCounter, and one value for count the current element position in the big List i caled RailCounter. In every turn u read from PhotosAll.Skip(RailCounter).Take(StandartCounter) and RailCounter += StandartCounter; The problem was CounterData must be static!