public bool HasFilter( 
   string filterID
)

{
  // Note: call within QueuedTask.Run()
  {
    //Note: Use HasFilter to check if a given filter id exists in the layer
    if (bsl.HasFilter(filter.ID))
      bsl.SetActiveFilter(filter.ID);
    var activeFilter = bsl.GetActiveFilter();

    //Clear the active filter
    bsl.ClearActiveFilter();
  }
}

{
  // Note: call within QueuedTask.Run()
  {
    //Note: Use HasFilter to check if a given filter id exists in the layer
    if (bsl.HasFilter(filter.ID))
      bsl.RemoveFilter(filter.ID);
    //Or remove all filters
    bsl.RemoveAllFilters();
  }
}