MainWindowViewModel.cs

public class MainWindowViewModel : ViewModelBase
{
    private CancellationToken _cancellationToken;
    private CancellationTokenSource _cancellationTokenSource = new();

    private int _pageIndex = 1;
        
    private ObservableCollection<IWallpaperInfo> _wallpapers = new();
    private string _searchString = "";

    public ObservableCollection<IWallpaperInfo> Wallpapers
    {
        get => _wallpapers;
        private set => this.RaiseAndSetIfChanged(ref _wallpapers, value);
    }
        
    public string SearchString
    {
        get => _searchString;
        set => this.RaiseAndSetIfChanged(ref _searchString, value);
    }
    
    public MainWindowViewModel()
    {
        CloseLastTask();

        this.WhenAnyValue(x => x.SearchString).Subscribe(OnSearchStringChanged);
    }

    public void VisibleChange()
    {
        IsVisible = !IsVisible;
    }

    private void OnSearchStringChanged(string newValue)
    {
        Dispatcher.UIThread.Post(TryLoadWallpapers);
    }

    private async void TryLoadWallpapers()
    {
        CloseLastTask();
        if (!await InternetSession.IsInternetConnection() || _cancellationToken.IsCancellationRequested) return;
        try
        {
            var addedWallpapers =
                await WallpaperPluginService.SelectedPlugin.Search(SearchString, _pageIndex, _cancellationToken).WaitAsync(_cancellationToken);
            _cancellationToken.ThrowIfCancellationRequested();
            Wallpapers = new ObservableCollection<IWallpaperInfo>(addedWallpapers.ToList());
        }
        catch (OperationCanceledException e)
        {
            Console.WriteLine("Close Task");
            // CloseLastTask();
            // TryLoadWallpapers();
        }
    }
    private void CloseLastTask()
    {
        _pageIndex = 1;
        _cancellationTokenSource.Cancel();
        _cancellationTokenSource = new CancellationTokenSource();
        _cancellationToken = _cancellationTokenSource.Token;
    }
}