public sealed class TinLayer : SurfaceLayer, ArcGIS.Desktop.Core.IMetadataInfo, IMetadataSource, System.ComponentModel.INotifyPropertyChanged  

{
  // find the first TIN layer
  tinLayer = MapView.Active.Map.GetLayersAsFlattenedList().OfType<TinLayer>().FirstOrDefault();

  // find the first Terrain layer
  terrainLayer = MapView.Active.Map.GetLayersAsFlattenedList().OfType<TerrainLayer>().FirstOrDefault();

  // find the first LAS dataset layer
  lasDatasetLayer = MapView.Active.Map.GetLayersAsFlattenedList().OfType<LasDatasetLayer>().FirstOrDefault();

  // find the first surface layer
  surfaceLayer = MapView.Active.Map.GetLayersAsFlattenedList().OfType<SurfaceLayer>().FirstOrDefault();
}

{
  string tinPath = @"d:\Data\Tin\TinDataset";
  var tinURI = new Uri(tinPath);

  var tinCP = new TinLayerCreationParams(tinURI);
  tinCP.Name = "My TIN Layer";
  tinCP.IsVisible = false;
  // Note: Needs QueuedTask to run
  {
    //Create the layer to the TIN
    tinLayer = LayerFactory.Instance.CreateLayer<TinLayer>(tinCP, map);
  }
}

{
  var tinCP_ds = new TinLayerCreationParams(tinDataset);
  tinCP_ds.Name = "My TIN Layer";
  tinCP_ds.IsVisible = false;

  //Create the layer to the TIN
  // Note: Needs QueuedTask to run
  {
    var tinLayer_ds = LayerFactory.Instance.CreateLayer<TinLayer>(tinCP_ds, map);
  }
}

{
  var tinCP_renderers = new TinLayerCreationParams(tinDataset)
  {
    Name = "My TIN layer",
    IsVisible = true
  };

  // define the node renderer - use defaults
  var node_rd = new TinNodeRendererDefinition();

  // define the face/surface renderer
  var face_rd = new TinFaceClassBreaksRendererDefinition();
  face_rd.ClassificationMethod = ClassificationMethod.NaturalBreaks;
  // accept default color ramp, breakCount

  // set up the renderer dictionary
  var rendererDict = new Dictionary<SurfaceRendererTarget, TinRendererDefinition>
{
  { SurfaceRendererTarget.Points, node_rd },
  { SurfaceRendererTarget.Surface, face_rd }
};

  // assign the dictionary to the creation params
  tinCP_renderers.RendererDefinitions = rendererDict;
  // Note: Needs QueuedTask to run
  {
    // create the layer
    var tinLayer_rd = LayerFactory.Instance.CreateLayer<TinLayer>(tinCP_renderers, MapView.Active.Map);
  }
}

{
  // applies to TIN layers only
  var nodeRendererDef = new TinNodeRendererDefinition();
  nodeRendererDef.Description = "Nodes";
  nodeRendererDef.Label = "Nodes";
  nodeRendererDef.SymbolTemplate = nodeSymbol.MakeSymbolReference();

  // Note: Needs QueuedTask to run
  {
    if (tinLayer.CanCreateRenderer(nodeRendererDef))
    {
      CIMTinRenderer renderer = tinLayer.CreateRenderer(nodeRendererDef);
      if (tinLayer.CanSetRenderer(renderer, SurfaceRendererTarget.Points))
        tinLayer.SetRenderer(renderer, SurfaceRendererTarget.Points);
    }
  }
}