public CIMElement GetDefinition()

//Modify an element's CIM properties.

//Perform on the worker thread
await QueuedTask.Run(() =>
{
  CIMElement CIMElm = element.GetDefinition();

  //Modify a CIM value

  element.SetDefinition(CIMElm);
});

//Modify an existing tableframe using CIM properties.

//Reference the active layout
Layout layout = LayoutView.Active.Layout;

//Perform on the worker thread
await QueuedTask.Run(() =>
{
  //Reference table frame
  TableFrame TF = layout.FindElement("Table Frame") as TableFrame;

  //Modify CIM properties
  CIMTableFrame cimTF = TF.GetDefinition() as CIMTableFrame;
  cimTF.Alternate1RowBackgroundCount = 1;
  cimTF.Alternate2RowBackgroundCount = 1;

  //Apply the changes
  TF.SetDefinition(cimTF);
});

//Set the CIM halo properties of a north arrow.

//Reference the first selected element (assumption is it is a north arrow)
Element northArrow = LayoutView.Active.GetSelectedElements().First();

//Perform on the worker thread
QueuedTask.Run(() =>
{
  //Get definition of north arrow...
  var cim = northArrow.GetDefinition() as CIMMarkerNorthArrow;
  
  //this halo symbol is 50% transparent, no outline (i.e. 0 width)
  //First construct a polygon symbol to use in the Halo
  //Polygon symbol will need a fill and a stroke
  var polyFill = SymbolFactory.Instance.ConstructSolidFill(ColorFactory.Instance.CreateRGBColor(0, 0, 0, 50));
  var polyStroke = SymbolFactory.Instance.ConstructStroke(ColorFactory.Instance.BlackRGB, 0);
  var haloPoly = SymbolFactory.Instance.ConstructPolygonSymbol(polyFill, polyStroke);
  
  //Set the north arrow defintion of HaloSymbol and HaloSize 
  ((CIMPointSymbol)cim.PointSymbol.Symbol).HaloSymbol = haloPoly;
  ((CIMPointSymbol)cim.PointSymbol.Symbol).HaloSize = 3;//size of the halo
    
  //Apply the CIM changes back to the element
  northArrow.SetDefinition(cim);
});

//Apply a background color to the map frame element using the CIM.

//Perform on the worker thread
QueuedTask.Run(() =>
{
  //Get the layout
  var myLayout = Project.Current.GetItems<LayoutProjectItem>()?.First().GetLayout();
  if (myLayout == null) return;

  //Get the map frame in the layout
  MapFrame mapFrame = myLayout.FindElement("New Map Frame") as MapFrame;
  if (mapFrame == null)
  {
    //TODO Handle null mapframe
    return;
  }

  //Get the map frame's definition in order to modify the background.
  var mapFrameDefn = mapFrame.GetDefinition() as CIMMapFrame;

  //Construct the polygon symbol to use to create a background
  var polySymbol = SymbolFactory.Instance.ConstructPolygonSymbol(
                 ColorFactory.Instance.BlueRGB, SimpleFillStyle.Solid);

  //Set the background
  mapFrameDefn.GraphicFrame.BackgroundSymbol =
                                   polySymbol.MakeSymbolReference();

  //Set the map frame definition
  mapFrame.SetDefinition(mapFrameDefn);
});

// The Locked property is displayed in the TOC as a lock symbol next
// to each element.  If locked the element can't be selected in the layout
// using the graphic selection tools.

//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 an element by name
    Element element = layout.FindElement("MyElement");
    if (element != null)
    {
      // Modify the Locked property via the CIM
      CIMElement CIMElement = element.GetDefinition() as CIMElement;
      CIMElement.Locked = true;
      element.SetDefinition(CIMElement);
    }
  }
});