Bounding Box XYZ Transform Property

public Transform Transform { get; set; }

private void RotateBoundingBox(View3D view3d)
{
    if (!view3d.IsSectionBoxActive)
    {
        TaskDialog.Show("Revit","The section box for View3D isn't active.");
        return;
    }
    BoundingBoxXYZ box = view3d.GetSectionBox();

    // Create a rotation transform to apply to the section box 
    XYZ origin = new XYZ(0, 0, 0);
    XYZ axis = new XYZ(0, 0, 1);

    // Rotate 30 degrees
    Transform rotate = Transform.CreateRotationAtPoint(axis, Math.PI/6.0, origin);

    // Transform the View3D's section box with the rotation transform
    box.Transform = box.Transform.Multiply(rotate);

    // Set the section box back to the view (requires an open transaction)
    view3d.SetSectionBox(box);
}