public IList<IsosurfaceDefinition> GetIsosurfaces()

{
  var variable = voxelLayer.GetVariableProfiles().First();
  var max = variable.MaxNumberOfIsosurfaces;
  if (max >= variable.GetIsosurfaces().Count)
  {
    //no more surfaces can be created on this variable
  }
}

{
  // Note: call within QueuedTask.Run()
  {
    var variable = voxelLayer.SelectedVariableProfile;

    //Change the color of the first surface for the given profile
    var surface = variable.GetIsosurfaces().FirstOrDefault();
    if (surface != null)
    {
      if (voxelLayer.Visualization != VoxelVisualization.Surface)
        voxelLayer.SetVisualization(VoxelVisualization.Surface);

      //Change the iso surface voxel value
      surface.Value = surface.Value * 0.9;

      //get a random color
      var count = new Random().Next(0, 100);
      var colors = ColorFactory.Instance.GenerateColorsFromColorRamp(
        ((CIMVoxelStretchRenderer)variable.Renderer).ColorRamp, count);

      var idx = new Random().Next(0, count - 1);
      surface.Color = colors[idx];
      //set the custom color flag true to lock the color
      //locking the color prevents it from being changed if the
      //renderer color range or color theme is updated
      surface.IsCustomColor = true;

      //update the surface
      variable.UpdateIsosurface(surface);
    }
  }
}

{
  // Note: call within QueuedTask.Run()
  {
    var variable = voxelLayer.SelectedVariableProfile;

    //delete the last surface
    var last_surface = variable.GetIsosurfaces().LastOrDefault();

    if (last_surface != null)
    {
      variable.DeleteIsosurface(last_surface);
    }

    //delete all the surfaces
    foreach (var surface in variable.GetIsosurfaces())
      variable.DeleteIsosurface(surface);

    //Optional - set visualization back to Volume
    if (variable.GetIsosurfaces().Count() == 0)
    {
      voxelLayer.SetVisualization(VoxelVisualization.Volume);
    }
  }
}