public ParallelOffset.Builder()

//Create parrallel features from the selected features

//find the roads layer
var roadsLayer = MapView.Active.Map.FindLayers("Roads").FirstOrDefault();

//instatiate paralleloffset builder and set parameters
var parOffsetBuilder = new ParallelOffset.Builder()
{
  Selection = MapView.Active.Map.GetSelection(),
  Template = roadsLayer.GetTemplate("Freeway"),
  Distance = 200,
  Side = ParallelOffset.SideType.Both,
  Corner = ParallelOffset.CornerType.Mitered,
  Iterations = 1,
  AlignConnected = false,
  CopyToSeparateFeatures = false,
  RemoveSelfIntersectingLoops = true
};

//create editoperation and execute
var parrallelOp = new EditOperation();
parrallelOp.Create(parOffsetBuilder);
parrallelOp.Execute();