public void RunInBackground()
        {
            if (_cancellationTokenSource == null)
            {
                _cancellationTokenSource = new CancellationTokenSource();
            }

            AsyncTaskDispose();
            _asyncTask = new CustomAsyncTask(this, _cancellationTokenSource.Token);
            _asyncTask.Execute(DocumentTaskType);
        }
 private void AsyncTaskDispose()
 {
     _asyncTask?.Dispose();
     _asyncTask = null;
 }