public sealed class TinDataset : ArcGIS.Core.Data.Dataset, System.IDisposable  

public async Task OpenTinDataset()
{
  try
  {
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() =>
    {
      string path = @"d:\Data\Tin";
      var fileConnection = new FileSystemConnectionPath(new Uri(path), FileSystemDatastoreType.Tin);

      using (FileSystemDatastore dataStore = new FileSystemDatastore(fileConnection))
      {
        // TIN is in a folder at d:\Data\Tin\TinDataset

        string dsName = "TinDataset";

        using (var dataset = dataStore.OpenDataset<ArcGIS.Core.Data.Analyst3D.TinDataset>(dsName))
        {

        }
      }
    });
  }
  catch (GeodatabaseNotFoundOrOpenedException exception)
  {
    // Handle Exception.
  }
}

//Must be on the QueuedTask.Run()

Envelope extent;
SpatialReference sr;
using (var tin = tinLayer.GetTinDataset())
{
  using (var tinDef = tin.GetDefinition())
  {
    extent = tinDef.GetExtent();
    sr = tinDef.GetSpatialReference();
  }
}

using (var terrain = terrainLayer.GetTerrain())
{
  using (var terrainDef = terrain.GetDefinition())
  {
    extent = terrainDef.GetExtent();
    sr = terrainDef.GetSpatialReference();
  }
}

using (var lasDataset = lasDatasetLayer.GetLasDataset())
{
  using (var lasDatasetDef = lasDataset.GetDefinition())
  {
    extent = lasDatasetDef.GetExtent();
    sr = lasDatasetDef.GetSpatialReference();
  }
}

//Must be on the QueuedTask.Run()

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

//Create the layer to the TIN

var tinLayer_ds = LayerFactory.Instance.CreateLayer<TinLayer>(tinCP_ds, map);

//Must be on the QueuedTask.Run()

var tinCP_renderers = new TinLayerCreationParams(tinDataset);
tinCP_renderers.Name = "My TIN layer";
tinCP_renderers.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>();
rendererDict.Add(SurfaceRendererTarget.Points, node_rd);
rendererDict.Add(SurfaceRendererTarget.Surface, face_rd);

// assign the dictionary to the creation params
tinCP_renderers.RendererDefinitions = rendererDict;

// create the layer
var tinLayer_rd = LayerFactory.Instance.CreateLayer<TinLayer>(tinCP_renderers, MapView.Active.Map);