public sealed class LasDatasetDefinition : ArcGIS.Core.Data.Definition, System.IDisposable  

{
  //Note: Use QueuedTask.Run to run on the MCT
  string path = @"d:\Data\LASDataset";
  var fileConnection = new FileSystemConnectionPath(new Uri(path), FileSystemDatastoreType.LasDataset);

  using (FileSystemDatastore dataStore = new FileSystemDatastore(fileConnection))
  {
    string name = "utrecht_tile.lasd";      // can specify with or without the .lasd extension

    using (var dataset = dataStore.GetDefinition<ArcGIS.Core.Data.Analyst3D.LasDatasetDefinition>(name))
    {
      //Use 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();
    }
  }
}