public void Modify( 
   Row row,
   string fieldName,
   object value
)

private void HookChangedEvent()
{
  // subscribe to the RowChangedEvent
  Table table = MapView.Active.Map.GetLayersAsFlattenedList().OfType<FeatureLayer>().FirstOrDefault().GetTable();
  RowChangedEvent.Subscribe(MyRowChangedEvent, table);
}

private void MyRowChangedEvent(RowChangedEventArgs args)
{
  // RowEvent callbacks are always called on the QueuedTask so there is no need 
  // to wrap your code within a QueuedTask.Run lambda.

  //example of modifying a field on a row that has been created
  var parentEditOp = args.Operation;

  // avoid recursion
  if (_lastEdit != args.Guid)
  {
    //update field on change
    parentEditOp.Modify(args.Row, "ZONING", "New");

    _lastEdit = args.Guid;
  }
}

//See "Change Annotation Text Graphic" for an alternative if TEXTSTRING is missing from the schema
await QueuedTask.Run(() =>
{
    //annoLayer is ~your~ Annotation layer...

    // use the inspector methodology
    var insp = new Inspector();
    insp.Load(annoLayer, oid);

    // make sure TextString attribute exists.
    //It is not guaranteed to be in the schema
    ArcGIS.Desktop.Editing.Attributes.Attribute att = insp.FirstOrDefault(a => a.FieldName == "TEXTSTRING");
    if (att != null)
    {
        insp["TEXTSTRING"] = "Hello World";

        //create and execute the edit operation
        EditOperation op = new EditOperation();
        op.Name = "Update annotation";
        op.Modify(insp);

        //OR using a Dictionary - again TEXTSTRING has to exist in the schema
        //Dictionary<string, object> newAtts = new Dictionary<string, object>();
        //newAtts.Add("TEXTSTRING", "hello world");
        //op.Modify(annoLayer, oid, newAtts);

        op.Execute();
    }
});

//must support editing!
var featSceneLayer = MapView.Active.Map.GetLayersAsFlattenedList()
                   .OfType<FeatureSceneLayer>().FirstOrDefault();
if (!featSceneLayer.HasAssociatedFeatureService || 
    !featSceneLayer.IsEditable)
  return;

var ok = await QueuedTask.Run(() =>
{
  var editOp = new EditOperation()
  {
    Name = "Edit FeatureSceneLayer Attributes",
    SelectModifiedFeatures = true
  };
  //make an inspector
  var inspector = new Inspector();
  //get the attributes for the specified oid
  inspector.Load(featSceneLayer, oid);
  inspector["PermitNotes"] = "test";//modify
  editOp.Modify(inspector);
  return editOp.Execute();//synchronous flavor
});