public bool HasValueChanged( 
   int index
)

// Attach an event handler to receive notifications when a row in the selected
// table is changed. The subscription targets the first <see cref="ArcGIS.Desktop.Mapping.FeatureLayer"/> found in
// the active map. Use this method to monitor and respond to edits made to table records within the current map
// context.
Table thisTable = MapView.Active.Map.GetLayersAsFlattenedList().OfType<FeatureLayer>().FirstOrDefault().GetTable();
RowChangedEvent.Subscribe(rowChangedEventArgs =>
  {
    // set the current row changed guid when you execute the Row.Store method
    // used for re-entry checking
    Guid _currentRowChangedGuid = new();
    // RowEvent callbacks are always called on the QueuedTask so there is no need 
    // to wrap your code within a QueuedTask.Run lambda.

    var row = rowChangedEventArgs.Row;

    // check for re-entry  (only if row.Store is called)
    if (_currentRowChangedGuid == rowChangedEventArgs.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
          rowChangedEventArgs.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 = rowChangedEventArgs.Guid;
      row.Store();
      _currentRowChangedGuid = Guid.Empty;
    }
  }, thisTable);