public sealed class TinTriangle : TinElement, System.IDisposable  

{
  using (ArcGIS.Core.Data.Analyst3D.TinNode nodeFromIndex = tinDataset.GetNodeByIndex(23))
  {
    //Do something with the node
  }

  using (ArcGIS.Core.Data.Analyst3D.TinEdge edgeFromIndex = tinDataset.GetEdgeByIndex(45))
  {
    //Do something with the edge
  }
  using (ArcGIS.Core.Data.Analyst3D.TinTriangle triangleFromIndex = tinDataset.GetTriangleByIndex(22))
  {
    //Do something with the triangle
  }
}

{
  // search all triangles that intersect the data extent
  using (ArcGIS.Core.Data.Analyst3D.TinTriangleCursor triangleSearchCursor = tinDataset.SearchTriangles(null))
  {
    while (triangleCursor.MoveNext())
    {
      using (ArcGIS.Core.Data.Analyst3D.TinTriangle triangleCurrent = triangleCursor.Current)
      {

      }
    }
  }

  // search within an extent
  ArcGIS.Core.Data.Analyst3D.TinTriangleFilter triangleFilter = new ArcGIS.Core.Data.Analyst3D.TinTriangleFilter();
  triangleFilter.FilterEnvelope = envelope;
  using (ArcGIS.Core.Data.Analyst3D.TinTriangleCursor triangleSearchCursor = tinDataset.SearchTriangles(triangleFilter))
  {
    while (triangleCursor.MoveNext())
    {
      using (ArcGIS.Core.Data.Analyst3D.TinTriangle triangleCurrent = triangleCursor.Current)
      {

      }
    }
  }

  // search all "inside" triangles
  triangleFilter = new ArcGIS.Core.Data.Analyst3D.TinTriangleFilter();
  triangleFilter.FilterType = ArcGIS.Core.Data.Analyst3D.TinFilterType.InsideDataArea;
  using (ArcGIS.Core.Data.Analyst3D.TinTriangleCursor triangleSearchCursor = tinDataset.SearchTriangles(triangleFilter))
  {
    while (triangleCursor.MoveNext())
    {
      using (ArcGIS.Core.Data.Analyst3D.TinTriangle triangleCurrent = triangleCursor.Current)
      {

      }
    }
  }
}

{
  // nodes, edges of the triangle
  var triNnodes = triangle.Nodes;
  var triEdges = triangle.Edges;

  // triangle geometry
  polygon = triangle.ToPolygon();
  // triangle length
  var triLength = triangle.Length;
  // triangle area 
  var triArea = triangle.Area;
  // is the triangle "inside"
  var isInsideTriangle = triangle.IsInsideDataArea;

  // triangle aspect and slope  (radians)
  var aspect = triangle.Aspect;
  var slope = triangle.Slope;

  // get centroid
  var centroid = triangle.GetCentroid();

  // get normal
  var normal = triangle.GetNormal();

  // get adjacent triangles
  var adjTriangles = triangle.GetAdjacentTriangles();

  // get area of triangle that falls between the z values
  double minZ = 1.0;
  double maxZ = 3.0;
  IReadOnlyList<Coordinate3D> coords = triangle.GetPointsBetweenZs(minZ, maxZ);
}

{
  // Note: Needs QueuedTask to run
  {
    // search all "inside" nodes
    using (ArcGIS.Core.Data.Analyst3D.TinNodeCursor nodeCursor = tinLayer.SearchNodes(null))
    {
      while (nodeCursor.MoveNext())
      {
        using ArcGIS.Core.Data.Analyst3D.TinNode node = nodeCursor.Current;
        //Use the node
      }
    }

    // search "inside" nodes with an extent
    ArcGIS.Core.Data.Analyst3D.TinNodeFilter nodeFilter = new ArcGIS.Core.Data.Analyst3D.TinNodeFilter();
    nodeFilter.FilterEnvelope = envelope;
    using (ArcGIS.Core.Data.Analyst3D.TinNodeCursor nodeCursor = tinLayer.SearchNodes(nodeFilter))
    {
      while (nodeCursor.MoveNext())
      {
        using ArcGIS.Core.Data.Analyst3D.TinNode node = nodeCursor.Current;
        //use the node
      }
    }

    // search for super nodes only
    var supernodeFilter = new ArcGIS.Core.Data.Analyst3D.TinNodeFilter();
    supernodeFilter.FilterEnvelope = tinLayer.GetTinDataset().GetSuperNodeExtent();
    supernodeFilter.DataElementsOnly = false;
    supernodeFilter.SuperNode = true;
    using (ArcGIS.Core.Data.Analyst3D.TinNodeCursor nodeCursor = tinLayer.SearchNodes(nodeFilter))
    {
      while (nodeCursor.MoveNext())
      {
        using ArcGIS.Core.Data.Analyst3D.TinNode node = nodeCursor.Current;
        //Use the node
      }
    }

    // search all edges within an extent
    //    this could include outside or edges attached to super nodes depending upon the extent
    ArcGIS.Core.Data.Analyst3D.TinEdgeFilter edgeFilterAll = new ArcGIS.Core.Data.Analyst3D.TinEdgeFilter();
    edgeFilterAll.FilterEnvelope = envelope;
    edgeFilterAll.DataElementsOnly = false;
    using (ArcGIS.Core.Data.Analyst3D.TinEdgeCursor edgeCursor = tinLayer.SearchEdges(edgeFilterAll))
    {
      while (edgeCursor.MoveNext())
      {
        using ArcGIS.Core.Data.Analyst3D.TinEdge edge = edgeCursor.Current;
        //Use the edge
      }
    }

    // search for hard edges in the TIN
    var edgeFilter = new ArcGIS.Core.Data.Analyst3D.TinEdgeFilter();
    edgeFilter.FilterByEdgeType = true;
    edgeFilter.EdgeType = ArcGIS.Core.Data.Analyst3D.TinEdgeType.HardEdge;
    using (ArcGIS.Core.Data.Analyst3D.TinEdgeCursor edgeCursor = tinLayer.SearchEdges(edgeFilter))
    {
      while (edgeCursor.MoveNext())
      {
        using ArcGIS.Core.Data.Analyst3D.TinEdge edge = edgeCursor.Current;
        //Use the edge
      }
    }

    // search for "inside" triangles in an extent
    ArcGIS.Core.Data.Analyst3D.TinTriangleFilter triangleFilter = new ArcGIS.Core.Data.Analyst3D.TinTriangleFilter();
    triangleFilter.FilterEnvelope = envelope;
    triangleFilter.DataElementsOnly = true;
    using (ArcGIS.Core.Data.Analyst3D.TinTriangleCursor triangleCursor = tinLayer.SearchTriangles(triangleFilter))
    {
      while (triangleCursor.MoveNext())
      {
        using ArcGIS.Core.Data.Analyst3D.TinTriangle triangle = triangleCursor.Current;
        //use the triangle
      }
    }
  }
}