public static IList<NorthArrowStyleItem> SearchNorthArrows( 
   StyleProjectItem styleProjectItem,
   string searchString
)

{
  //Create a north arrow using a style.

  //Search for a style project item by name
  StyleProjectItem arcgis2dStyles = Project.Current.GetItems<StyleProjectItem>()
                    .First(si => si.Name == "ArcGIS 2D");

  //Construct on the worker thread

  NorthArrowStyleItem naStyleItem = arcgis2dStyles.SearchNorthArrows(
                "ArcGIS North 13").FirstOrDefault();

  //Reference the map frame and define the location
  MapFrame newFrame = layout.FindElement("New Map Frame") as MapFrame;
  Coordinate2D nArrow = new Coordinate2D(6, 2.5);

  //Construct the north arrow

  var naInfo = new NorthArrowInfo()
  {
    MapFrameName = newFrame.Name,
    NorthArrowStyleItem = naStyleItem
  };
  var newNorthArrow = ElementFactory.Instance.CreateMapSurroundElement(
                          layout, nArrow.ToMapPoint(), naInfo);
}

{
  //Note: Must be on QueuedTask.Run

  //Build geometry
  Coordinate2D center = new Coordinate2D(7, 5.5);

  //Reference a North Arrow in a style
  StyleProjectItem stylePrjItm = Project.Current.GetItems<StyleProjectItem>()
                                 .FirstOrDefault(item => item.Name == "ArcGIS 2D");
  NorthArrowStyleItem naStyleItm = stylePrjItm.SearchNorthArrows(
                                         "ArcGIS North 10")[0];

  //Reference MF, create north arrow and add to layout 

  var mf = layout.FindElement("Map Frame") as MapFrame;
  var narrow_info = new NorthArrowInfo()
  {
    MapFrameName = mf.Name,
    NorthArrowStyleItem = naStyleItm
  };
  var arrowElm = (NorthArrow)ElementFactory.Instance.CreateMapSurroundElement(
    layout, center.ToMapPoint(), narrow_info) as NorthArrow;
  arrowElm.SetName("New North Arrow");
  arrowElm.SetHeight(1.75);
  arrowElm.SetX(7);
  arrowElm.SetY(6);
}

{
    //Search for north arrows
    //Note: styleProjectItem was created above in the variable initialization section
    //Note: Needs QueuedTask to run
    styleProjectItem.SearchNorthArrows("searchString");
}