public TinEditor( 
   TinDataset tinDataset
)

{
  TinEditor tinEditorFromDataset = new TinEditor(tinDataset);
  bool isInEditMode = tinEditorFromDataset.IsInEditMode;  // isInEditMode = true
}

{
  string tinPath = "C:\\Tin"; //original TIN path
  // Create an instance of TinEditor from an existing TinDataset
  tinEditor = new TinEditor(tinDataset);
  int numNodes = tinDataset.GetNodeCount();  // numNodes = 10
  tinEditor.AddPointZ(pointZ, 7);

  // Calling SaveEdits modifies the existing TIN
  tinEditor.SaveEdits();
  numNodes = tinDataset.GetNodeCount();  // numNodes = 11

  // Adding twenty points
  tinEditor.AddMassPoints(points, 10, 112.5);

  // Calling SaveAs creates a new TIN on disk, and 
  // the tin editor points to the new TIN.
  string tinPath2 = "C:\\Tin2";
  tinEditor.SaveAs(tinPath2, true);

  tinEditor.StopEditing(true);
  var connection = new FileSystemConnectionPath(new Uri(Path.GetDirectoryName(tinPath2)), FileSystemDatastoreType.Tin);
  using (FileSystemDatastore dataStore = new FileSystemDatastore(connection))
  {
    // See https://github.com/esri/arcgis-pro-sdk/wiki/ProConcepts-3D-Analyst-Data#working-with-tin-data
    TinDataset tinDataset2 = dataStore.OpenDataset<ArcGIS.Core.Data.Analyst3D.TinDataset>(Path.GetFileName(tinPath2));
    numNodes = tinDataset2.GetNodeCount(); // numNodes = 31
  }

  // The edits still show up in the original TIN while it is in memory, but if you open it
  // again you will see that it only has the edits that were saved before SaveAs was called.
  numNodes = tinDataset.GetNodeCount(); // numNodes = 31
  var connection2 = new FileSystemConnectionPath(new Uri(Path.GetDirectoryName(tinPath)), FileSystemDatastoreType.Tin);
  using (FileSystemDatastore dataStore = new FileSystemDatastore(connection))
  {
    // See https://github.com/esri/arcgis-pro-sdk/wiki/ProConcepts-3D-Analyst-Data#working-with-tin-data
    tinDataset = dataStore.OpenDataset<ArcGIS.Core.Data.Analyst3D.TinDataset>(Path.GetFileName(tinPath));
    numNodes = tinDataset.GetNodeCount(); // numNodes = 11
  }
}