Here is the correct code:
//DataRow dr = ((DataTable)gridControlT.DataSource).Rows[e.RowHandle];
DataRow dr = ((GridView)sender).GetDataRow(e.RowHandle);
Row handle gets the handle(not the index) of the row that contains the processed cell. Row handles define the order in which rows are displayed within a View. This order takes into account any sorting and filtering settings applied to the View.
Related help-article : Identifying Rows and Cards