partial class Examples
{
  private static List<RhinoObject> m_line_objects = new List<RhinoObject>();

  public static Result DisplayOrder(RhinoDoc doc)
  {
    // make lines thick so draw order can be easily seen
    var dm = DisplayModeDescription.GetDisplayModes().Single(x => x.EnglishName == "Wireframe");
    var original_thikcness = dm.DisplayAttributes.CurveThickness;
    dm.DisplayAttributes.CurveThickness = 10;
    DisplayModeDescription.UpdateDisplayMode(dm);

    AddLine(Point3d.Origin, new Point3d(10,10,0), Color.Red, doc);
    AddLine(new Point3d(10,0,0), new Point3d(0,10,0), Color.Blue, doc);
    AddLine(new Point3d(8,0,0), new Point3d(8,10,0), Color.Green, doc);
    AddLine(new Point3d(0,3,0), new Point3d(10,3,0), Color.Yellow, doc);
    doc.Views.Redraw();
    Pause("draw order: 1st line drawn in front, last line drawn in the back.  Any key to continue ...");

    //all objects have a DisplayOrder of 0 by default so changing it to 1 moves it to the front.  Here we move the 2nd line (blue) to the front
    m_line_objects[1].Attributes.DisplayOrder = 1;
    m_line_objects[1].CommitChanges();
    doc.Views.Redraw();
    Pause("Second (blue) line now in front.  Any key to continue ...");

    for (int i = 0; i < m_line_objects.Count; i++)
    {
      m_line_objects[i].Attributes.DisplayOrder = i;
      m_line_objects[i].CommitChanges();
    }
    doc.Views.Redraw();
    Pause("Reverse order of original lines, i.e., Yellow 1st and Red last.  Any key to continue ...");

    // restore original line thickness
    dm.DisplayAttributes.CurveThickness = original_thikcness;
    DisplayModeDescription.UpdateDisplayMode(dm);

    doc.Views.Redraw();
    return Result.Success;
  }

  private static void Pause(string msg)
  {
    ObjRef obj_ref;
    var rc = RhinoGet.GetOneObject(msg, true, ObjectType.AnyObject, out obj_ref);
  }

  private static void AddLine(Point3d from, Point3d to, Color color, RhinoDoc doc)
  {
    var guid = doc.Objects.AddLine(from, to);
    var obj = doc.Objects.Find(guid);
    m_line_objects.Add(obj);
    obj.Attributes.ObjectColor = color;
    obj.Attributes.ColorSource = ObjectColorSource.ColorFromObject;
    obj.CommitChanges();
  }
}

Partial Friend Class Examples
  Private Shared m_line_objects As New List(Of RhinoObject)()

  Public Shared Function DisplayOrder(ByVal doc As RhinoDoc) As Result
	' make lines thick so draw order can be easily seen
	Dim dm = DisplayModeDescription.GetDisplayModes().Single(Function(x) x.EnglishName = "Wireframe")
	Dim original_thikcness = dm.DisplayAttributes.CurveThickness
	dm.DisplayAttributes.CurveThickness = 10
	DisplayModeDescription.UpdateDisplayMode(dm)

	AddLine(Point3d.Origin, New Point3d(10,10,0), Color.Red, doc)
	AddLine(New Point3d(10,0,0), New Point3d(0,10,0), Color.Blue, doc)
	AddLine(New Point3d(8,0,0), New Point3d(8,10,0), Color.Green, doc)
	AddLine(New Point3d(0,3,0), New Point3d(10,3,0), Color.Yellow, doc)
	doc.Views.Redraw()
	Pause("draw order: 1st line drawn in front, last line drawn in the back.  Any key to continue ...")

	'all objects have a DisplayOrder of 0 by default so changing it to 1 moves it to the front.  Here we move the 2nd line (blue) to the front
	m_line_objects(1).Attributes.DisplayOrder = 1
	m_line_objects(1).CommitChanges()
	doc.Views.Redraw()
	Pause("Second (blue) line now in front.  Any key to continue ...")

	For i As Integer = 0 To m_line_objects.Count - 1
	  m_line_objects(i).Attributes.DisplayOrder = i
	  m_line_objects(i).CommitChanges()
	Next i
	doc.Views.Redraw()
	Pause("Reverse order of original lines, i.e., Yellow 1st and Red last.  Any key to continue ...")

	' restore original line thickness
	dm.DisplayAttributes.CurveThickness = original_thikcness
	DisplayModeDescription.UpdateDisplayMode(dm)

	doc.Views.Redraw()
	Return Result.Success
  End Function

  Private Shared Sub Pause(ByVal msg As String)
	Dim obj_ref As ObjRef = Nothing
	Dim rc = RhinoGet.GetOneObject(msg, True, ObjectType.AnyObject, obj_ref)
  End Sub

  Private Shared Sub AddLine(ByVal [from] As Point3d, ByVal [to] As Point3d, ByVal color As Color, ByVal doc As RhinoDoc)
	Dim guid = doc.Objects.AddLine([from], [to])
	Dim obj = doc.Objects.Find(guid)
	m_line_objects.Add(obj)
	obj.Attributes.ObjectColor = color
	obj.Attributes.ColorSource = ObjectColorSource.ColorFromObject
	obj.CommitChanges()
  End Sub
End Class

from System.Collections.Generic import *
from System.Drawing import *
from Rhino import *
from Rhino.Commands import *
from Rhino.Display import *
from Rhino.Geometry import *
from Rhino.Input import *
from Rhino.DocObjects import *
from scriptcontext import doc

m_line_objects = []

def RunCommand():
    # make lines thick so draw order can be easily seen
    wfdm = [dm for dm in DisplayModeDescription.GetDisplayModes() if dm.EnglishName == "Wireframe"][0]
    original_thikcness = wfdm.DisplayAttributes.CurveThickness
    wfdm.DisplayAttributes.CurveThickness = 10
    DisplayModeDescription.UpdateDisplayMode(wfdm)

    AddLine(Point3d.Origin, Point3d(10,10,0), Color.Red, doc)
    AddLine(Point3d(10,0,0), Point3d(0,10,0), Color.Blue, doc)
    AddLine(Point3d(8,0,0), Point3d(8,10,0), Color.Green, doc)
    AddLine(Point3d(0,3,0), Point3d(10,3,0), Color.Yellow, doc)
    doc.Views.Redraw()
    Pause("draw order: 1st line drawn in front, last line drawn in the back.  Any key to continue ...")

    #all objects have a DisplayOrder of 0 by default so changing it to 1 moves it to the front.  Here we move the 2nd line (blue) to the front
    m_line_objects[1].Attributes.DisplayOrder = 1
    m_line_objects[1].CommitChanges()
    doc.Views.Redraw()
    Pause("Second (blue) line now in front.  Any key to continue ...")

    for i in range(1, m_line_objects.Count):
        m_line_objects[i].Attributes.DisplayOrder = i
        m_line_objects[i].CommitChanges()

    doc.Views.Redraw()
    Pause("Reverse order of original lines, i.e., Yellow 1st and Red last.  Any key to continue ...")

    # restore original line thickness
    wfdm.DisplayAttributes.CurveThickness = original_thikcness
    DisplayModeDescription.UpdateDisplayMode(wfdm)

    doc.Views.Redraw()
    return Result.Success

def Pause(msg):
    rc, obj_ref = RhinoGet.GetOneObject(msg, True, ObjectType.AnyObject)

def AddLine(from_pt, to_pt, color, doc):
    guid = doc.Objects.AddLine(from_pt, to_pt)
    obj = doc.Objects.Find(guid)
    m_line_objects.Add(obj)
    obj.Attributes.ObjectColor = color
    obj.Attributes.ColorSource = ObjectColorSource.ColorFromObject
    obj.CommitChanges()

if __name__ == "__main__":
    RunCommand()