public Nullable<double> Value {get; set;}

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

//Visualization must be surface
if (voxelLayer.Visualization != VoxelVisualization.Surface)
    voxelLayer.SetVisualization(VoxelVisualization.Surface);

//Get the variable profile on which to create the iso surface
var variable = voxelLayer.SelectedVariableProfile;

// o Visualization must be Surface
// o Variable profile must be continuous
// o Variable MaxNumberofIsoSurfaces must not have been reached...
if (variable.CanCreateIsosurface)
{
    //Note: calling create if variable.CanCreateIsosurface == false
    //will trigger an InvalidOperationException

    //Specify a voxel value for the iso surface
    //At 2.x - 
    //var min = variable.GetVariableStatistics().MinimumValue;
    //var max = variable.GetVariableStatistics().MaximumValue;

    var min = variable.Statistics.MinimumValue;
    var max = variable.Statistics.MaximumValue;
    var mid = (max + min) / 2;

    //color range (i.e. values that are being rendered)
    var renderer = variable.Renderer as CIMVoxelStretchRenderer;
    var color_min = renderer.ColorRangeMin;
    var color_max = renderer.ColorRangeMax;

    //keep the surface within the current color range (or it
    //won't render)
    if (mid < color_min)
    {
        mid = renderer.ColorRangeMin;
    }
    else if (mid > color_max)
    {
        mid = renderer.ColorRangeMax;
    }

    //Create the iso surface
    var suffix = Math.Truncate(mid * 100) / 100;
    variable.CreateIsosurface(new IsosurfaceDefinition()
    {
        Name = $"Surface {suffix}",
        Value = mid,
        IsVisible = true
    });
}

//var voxelLayer = ... ;
//Must be on the 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);
}