public Task<int> SelectAsync( 
   LasPointSelectionFilter selectionFilter,
   SelectionCombinationMethod method
)

{
  // must be on MCT 

  // create the filter
  var filter = new LasPointSelectionFilter();
  // set the filter geometry
  // don't set VisiblePoints, ClassCodes - use the existing layer values
  filter.FilterGeometry = polygon;

  // perform the selection
  var selCount = await lasDatasetLayer.SelectAsync(filter, SelectionCombinationMethod.New);

  // set up a second filter and configure the VisiblePoints, ClassCodes
  // note that the ClassCodes is using only (4,5)
  // whereas the layers setting is (3,4,5)
  var filter2 = new LasPointSelectionFilter();
  filter2.VisiblePoints = true;
  filter2.ClassCodes = new List<int>() { 4, 5 };
  filter2.FilterGeometry = polygon;

  // perform the selection
  selCount = await lasDatasetLayer.SelectAsync(filter2, SelectionCombinationMethod.New);
}

{
  // must be on MCT 

  var clusterFilter = new LasPointClusterSelectionFilter();
  clusterFilter.VisiblePoints = true;
  clusterFilter.ClassCodes = new List<int>();  // empty list means all classification codes
  clusterFilter.FilterGeometry = polygon;

  clusterFilter.SearchRadius = 0.5; // meters
  clusterFilter.MaximumNumberOfPoints = 500;

  var clusterSelCount = await lasDatasetLayer.SelectAsync(clusterFilter, SelectionCombinationMethod.New);
}

{
  // must be on MCT 

  var planeFilter = new LasPointPlaneSelectionFilter();
  planeFilter.VisiblePoints = true;
  planeFilter.ClassCodes = new List<int>();  // empty list means all classification codes
  planeFilter.FilterGeometry = polygon;

  planeFilter.ClusteringDistance = 0.3; // meters
  planeFilter.MaximumDistance = 500;
  planeFilter.PlaneTolerance = 0.152; // meters

  var planeSelCount = await lasDatasetLayer.SelectAsync(planeFilter, SelectionCombinationMethod.New);
}

{
  // must be on MCT 

  var railFilter = new LasPointRailSelectionFilter();
  railFilter.VisiblePoints = true;
  railFilter.ClassCodes = new List<int>();  // empty list means all classification codes
  railFilter.FilterGeometry = polygon;

  // configure a few of the properties and accept defaults for others
  railFilter.SearchRadius = 0.5; // meters
  railFilter.RailThickness = 0.2; // meters
  railFilter.MaximumLength = 225; // meters

  var railSelCount = await lasDatasetLayer.SelectAsync(railFilter, SelectionCombinationMethod.New);
}

{
  // must be on MCT 

  var pipelineFilter = new LasPointPipelineSelectionFilter();

  pipelineFilter.VisiblePoints = true;
  pipelineFilter.ClassCodes = new List<int>();  // empty list means all classification codes
  pipelineFilter.FilterGeometry = polygon;

  // configure a few of the properties and accept defaults for others
  pipelineFilter.ApplyWindCorrection = true;
  pipelineFilter.MinimumLength = 25;  // meters

  var pipelineSelCount = await lasDatasetLayer.SelectAsync(pipelineFilter, SelectionCombinationMethod.New);
}