public bool HasFilter( 
   string filterID
)

//Must be called on the MCT
//Note: Use HasFilter to check if a given filter id exists in the layer
//var bsl = ...;
if (bsl.HasFilter(filter1.ID))
  bsl.SetActiveFilter(filter1.ID);
var activeFilter = bsl.GetActiveFilter();

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

//var bsl = ...;
//Note: Use HasFilter to check if a given filter id exists in the layer
//Must be called on the MCT
if (bsl.HasFilter(filter1.ID))
  bsl.RemoveFilter(filter1.ID);
//Or remove all filters
bsl.RemoveAllFilters();