public double ClusteringDistance {get; set;}

// must be on MCT 

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

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

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