public Envelope GetSuperNodeExtent()

{
  var superNodeExtent = tinDataset.GetSuperNodeExtent();
}

{
  // 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
      }
    }
  }
}