public class TerrainLayerCreationParams : LayerCreationParams 

{
  // Note: Needs QueuedTask to run
  {
    string terrainPath = @"d:\Data\Terrain\filegdb_Containing_A_Terrain.gdb\FeatureDataset\Terrain_name";
    var terrainURI = new Uri(terrainPath);

    var terrainCP = new TerrainLayerCreationParams(terrainURI);
    terrainCP.Name = "My Terrain Layer";
    terrainCP.IsVisible = false;
    // Note: Needs QueuedTask to run
    {
      //Create the layer to the terrain
      terrainLayer = LayerFactory.Instance.CreateLayer<TerrainLayer>(terrainCP, map);
    }
  }
}

{
  var terrainCP_ds = new TerrainLayerCreationParams(terrain);
  terrainCP_ds.Name = "My Terrain Layer";
  terrainCP_ds.IsVisible = true;

  //Create the layer to the terrain
  // Note: Needs QueuedTask to run
  {
    var terrainLayer_ds = LayerFactory.Instance.CreateLayer<TerrainLayer>(terrainCP_ds, map);
  }
}

{
  var terrainCP_renderers = new TerrainLayerCreationParams(terrain);
  terrainCP_renderers.Name = "My LAS Layer";
  terrainCP_renderers.IsVisible = true;

  // define the edge type renderer - use defaults
  var edgeRD = new TinBreaklineRendererDefinition();

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

  // define the dirty area renderer - use defaults
  var dirtyAreaRD = new TerrainDirtyAreaRendererDefinition();

  // add renderers to dictionary
  var t_dict = new Dictionary<SurfaceRendererTarget, TinRendererDefinition>();
  t_dict.Add(SurfaceRendererTarget.Edges, edgeRD);
  t_dict.Add(SurfaceRendererTarget.Surface, faceRD);
  t_dict.Add(SurfaceRendererTarget.DirtyArea, dirtyAreaRD);

  // assign dictionary to creation params
  terrainCP_renderers.RendererDefinitions = t_dict;
  // Note: Needs QueuedTask to run
  {
    //Create the layer to the terrain
    var terrainLayer_rd = LayerFactory.Instance.CreateLayer<TerrainLayer>(terrainCP_renderers, map);
  }
}