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

{
  //Note: This snippet requires to be run on the MCT (Main CIM Thread)
  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))
    {
      //Do something with the dataset
    }
  }
}

{
  //Note: Needs QueuedTask to run
  {
    using (var tin = tinLayer.GetTinDataset())
    {
      using var tinDef = tin.GetDefinition();
      Envelope extent = tinDef.GetExtent();
      SpatialReference sr = tinDef.GetSpatialReference();
    }

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

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

{
  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);
  }
}