public ScaleBarStyleItem ScaleBarStyleItem {get; set;}

//Create a scale bar for a specific map frame and assign a scale bar style item.

//Construct on the worker thread
await QueuedTask.Run(() =>
{
  //Reference a North Arrow in a style
  StyleProjectItem stylePrjItm = Project.Current.GetItems<StyleProjectItem>().FirstOrDefault(item => item.Name == "ArcGIS 2D");
  ScaleBarStyleItem sbStyleItm = stylePrjItm.SearchScaleBars("Double Alternating Scale Bar 1")[0];

  //Build geometry
  Coordinate2D center = new Coordinate2D(7, 8);

  //Reference MF, create north arrow and add to layout 
  MapFrame mf = layout.FindElement("New Map Frame") as MapFrame;
  if (mf == null)
  {
    ArcGIS.Desktop.Framework.Dialogs.MessageBox.Show("Map frame not found", "WARNING");
    return;
  }

  //At 2.x -
  //ScaleBar sbElm = LayoutElementFactory.Instance.CreateScaleBar(layout, center, mf, sbStyleItm);
  //sbElm.SetName("New Scale Bar");
  //sbElm.SetWidth(2);
  //sbElm.SetX(6);
  //sbElm.SetY(7.5); 

  var sbInfo = new ScaleBarInfo()
  {
    MapFrameName = mf.Name,
    ScaleBarStyleItem = sbStyleItm
  };
  var sbElm = ElementFactory.Instance.CreateMapSurroundElement(
                                      layout, center.ToMapPoint(), sbInfo, "New Scale Bar") as ScaleBar;
  sbElm.SetWidth(2);
  sbElm.SetX(6);
  sbElm.SetY(7.5);
});

//Create a scale bar using a style.

//Search for a style project item by name
StyleProjectItem arcgis_2dStyle = Project.Current.GetItems<StyleProjectItem>()
                            .First(si => si.Name == "ArcGIS 2D");

//Construct on the worker thread
await QueuedTask.Run(() =>
{
  //Reference the specific scale bar by name 
  ScaleBarStyleItem scaleBarItem = arcgis_2dStyle.SearchScaleBars(
                     "Double Alternating Scale Bar").FirstOrDefault();

  //Reference the map frame and define the location
  MapFrame myMapFrame = layout.FindElement("Map Frame") as MapFrame;
  Coordinate2D coord2D = new Coordinate2D(10.0, 7.0);

  //Construct the scale bar
  //At 2.x - LayoutElementFactory.Instance.CreateScaleBar(
  //             layout, coord2D, myMapFrame, scaleBarItem);
  var sbarInfo = new ScaleBarInfo()
  {
    MapFrameName = myMapFrame.Name,
    ScaleBarStyleItem = scaleBarItem
  };
  ElementFactory.Instance.CreateMapSurroundElement(
          layout, coord2D.ToMapPoint(), sbarInfo);
});

//Must be on QueuedTask.Run(() => { ...

//Build geometry
Coordinate2D ll = new Coordinate2D(5.0, 8);
Coordinate2D ur = new Coordinate2D(6.0, 9);
Envelope sbEnv = EnvelopeBuilderEx.CreateEnvelope(ll, ur);

//Reference a Scale Bar in a style
StyleProjectItem stylePrjItm = Project.Current.GetItems<StyleProjectItem>()
                             .FirstOrDefault(item => item.Name == "ArcGIS 2D");
ScaleBarStyleItem sbStyleItm = stylePrjItm.SearchScaleBars(
                              "Scale Line 1")[0];
//ScaleBarStyleItem sbStyleItm = stylePrjItm.SearchScaleBars(
//                                           "Stepped Scale Line")[0];
//ScaleBarStyleItem sbStyleItm = stylePrjItm.SearchScaleBars(
//                                            "Scale Line 2")[0];

//Create Scale Bar
ScaleBarInfo sbInfo = new ScaleBarInfo()
{
  MapFrameName = mapFrame.Name,
  ScaleBarStyleItem = sbStyleItm
};

var sbElm = ElementFactory.Instance.CreateMapSurroundElement(
                  layout, sbEnv, sbInfo, "ScaleBar Line") as ScaleBar;