public sealed class ScaleBar : MapSurround, ArcGIS.Desktop.Mapping.IElement, System.ComponentModel.INotifyPropertyChanged, System.IComparable, System.IDisposable, System.IEquatable<Element>  

//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);
});

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

//Build geometry
Coordinate2D ll = new Coordinate2D(5.0, 6);
Coordinate2D ur = new Coordinate2D(6.0, 7);
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(
             "Alternating Scale Bar 1")[0];
//ScaleBarStyleItem sbStyleItm = stylePrjItm.SearchScaleBars(
//                                   "Double Alternating Scale Bar 1")[0];
//ScaleBarStyleItem sbStyleItm = stylePrjItm.SearchScaleBars(
//                                    "Hollow Scale Bar 1")[0];

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

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

//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;

//Update a map surround.

//Perform on the worker thread
QueuedTask.Run(() =>
{
  // Reference and load the layout associated with the layout item
  Layout layout = layoutItem.GetLayout();
  if (layout != null)
  {
    // Reference a scale bar element by name
    MapSurround scaleBar = layout.FindElement("MyScaleBar") as MapSurround;

    // Reference a map frame element by name
    MapFrame mf = layout.FindElement("MyMapFrame") as MapFrame;

    if ((scaleBar != null) && (mf != null))
      //Set the scale bar to the newly referenced map frame
      scaleBar.SetMapFrame(mf);
  }
});