public class SectionDefinition 

var surfaces = MapView.Active.GetSelectedIsosurfaces();
//set selected w/ MapView.Active.SelectVoxelIsosurface(isoSurface)
var slices = MapView.Active.GetSelectedSlices();
//set selected w/ MapView.Active.SelectVoxelSlice(slice)
var sections = MapView.Active.GetSelectedSections();
//set selected w/ MapView.Active.SelectVoxelSection(section)
var locked_sections = MapView.Active.GetSelectedLockedSections();
//set selected w/ MapView.Active.SelectVoxelLockedSection(locked_section)

//var voxelLayer = ... ;
//Must be on the QueuedTask.Run()

//At 2.x -
//var section = voxelLayer.GetSections().FirstOrDefault();
//var section2 = voxelLayer.GetSections().First(sec => sec.Id == my_section_id);

//Use the SelectedVariableProfile to get the sections currently in the TOC
//via its associated volume
var volume = voxelLayer.SelectedVariableProfile.Volume;

var section = volume.GetSections().FirstOrDefault();
var section2 = volume.GetSections().First(sec => sec.ID == my_section_id);

//var voxelLayer = ... ;
//Must be on the QueuedTask.Run()

if (voxelLayer.Visualization != VoxelVisualization.Surface)
    voxelLayer.SetVisualization(VoxelVisualization.Surface);
voxelLayer.SetSectionContainerExpanded(true);
voxelLayer.SetSectionContainerVisibility(true);

//At 2.x - var sections = voxelLayer.GetSections();

//Use the SelectedVariableProfile to get the sections currently in the TOC
//via its associated volume
var volume = voxelLayer.SelectedVariableProfile.Volume;
var sections = volume.GetSections();

//var voxelLayer = ... ;
//Must be on the QueuedTask.Run()

var section = MapView.Active?.GetSelectedSections()?.FirstOrDefault();
if (section != null)
{

}

//var voxelLayer = ... ;
//Must be on the QueuedTask.Run()

VoxelLayer voxelLayer = null;
var section = MapView.Active?.GetSelectedSections()?.FirstOrDefault();
if (section != null)
{
    voxelLayer = section.Layer;
    //TODO - use the layer
}