partial class Examples
{
  public static Result DuplicateObject(RhinoDoc doc)
  {
    ObjRef obj_ref;
    var rc = RhinoGet.GetOneObject("Select object to duplicate", false, ObjectType.AnyObject, out obj_ref);
    if (rc != Result.Success)
      return rc;
    var rhino_object = obj_ref.Object();

    var geometry_base = rhino_object.DuplicateGeometry();
    if (geometry_base != null)
      if (doc.Objects.Add(geometry_base) != Guid.Empty)
        doc.Views.Redraw();

    return Result.Success;
  }
}

from System import *
from Rhino import *
from Rhino.Commands import *
from Rhino.DocObjects import *
from Rhino.Input import *
from scriptcontext import doc

def RunCommand():

    rc, obj_ref = RhinoGet.GetOneObject("Select object to duplicate", False, ObjectType.AnyObject)
    if rc != Result.Success:
        return rc
    rhino_object = obj_ref.Object()

    geometry_base = rhino_object.DuplicateGeometry()
    if geometry_base != None:
        if doc.Objects.Add(geometry_base) != Guid.Empty:
            doc.Views.Redraw()

    return Result.Success

if __name__ == "__main__":
    RunCommand()