public bool HasValueChanged( 
   int index
)

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

private Guid _currentRowChangedGuid = Guid.Empty;
protected void OnRowChangedEvent(RowChangedEventArgs args)
{
  // RowEvent callbacks are always called on the QueuedTask so there is no need 
  // to wrap your code within a QueuedTask.Run lambda.

  var row = args.Row;

  // check for re-entry  (only if row.Store is called)
  if (_currentRowChangedGuid == args.Guid)
    return;

  var fldIdx = row.FindField("POLICE_DISTRICT");
  if (fldIdx != -1)
  {
    //Validate any change to �police district�
    //   cancel the edit if validation on the field fails
    if (row.HasValueChanged(fldIdx))
    {
      // cancel edit with invalid district (5)
      var value = row["POLICE_DISTRICT"].ToString();
      if (value == "5")
      {
        //Cancel edits with invalid �police district� values
        args.CancelEdit($"Police district {row["POLICE_DISTRICT"]} is invalid");
      }
    }

    // update the description field
    row["Description"] = "Row Changed";

    //  this update with cause another OnRowChanged event to occur
    //  keep track of the row guid to avoid recursion
    _currentRowChangedGuid = args.Guid;
    row.Store();
    _currentRowChangedGuid = Guid.Empty;
  }
}