public void SetDisplayFilter( 
   LasPointDisplayFilterType filtertype
)

{
  // Note: Needs QueuedTask to run
  {
    // get the current display filter
    LasPointDisplayFilter ptFilter = lasDatasetLayer.GetDisplayFilter();
    // display only ground points
    lasDatasetLayer.SetDisplayFilter(LasPointDisplayFilterType.Ground);

    // display first return points
    lasDatasetLayer.SetDisplayFilter(LasPointDisplayFilterType.FirstReturnPoints);

    // set display filter to a set of classification codes
    List<int> classifications = new List<int>() { 4, 5, 7, 10 };
    lasDatasetLayer.SetDisplayFilter(classifications);

    // set display filter to a set of returns
    List<ArcGIS.Core.Data.Analyst3D.LasReturnType> returns = new List<ArcGIS.Core.Data.Analyst3D.LasReturnType>()
        { ArcGIS.Core.Data.Analyst3D.LasReturnType.ReturnFirstOfMany};
    lasDatasetLayer.SetDisplayFilter(returns);

    // set up a display filter
    var newDisplayFilter = new LasPointDisplayFilter();
    newDisplayFilter.Returns = new List<ArcGIS.Core.Data.Analyst3D.LasReturnType>()
        { ArcGIS.Core.Data.Analyst3D.LasReturnType.ReturnFirstOfMany, ArcGIS.Core.Data.Analyst3D.LasReturnType.ReturnLastOfMany};
    newDisplayFilter.ClassCodes = new List<int>() { 2, 4 };
    newDisplayFilter.KeyPoints = true;
    newDisplayFilter.WithheldPoints = false;
    newDisplayFilter.SyntheticPoints = false;
    newDisplayFilter.NotFlagged = false;
    lasDatasetLayer.SetDisplayFilter(returns);
  }
}