private void ShowAllTransactions <AdminMethod>(string nula, string nulb, string nulc)
 {
     try
     {
         List <Transaction> transactions = Stregsystem.GetTransactions(null, 0);
         UI.DisplayTransactions(transactions);
     }
     catch (ArgumentNullException)
     {
         UI.DisplayProducts(Stregsystem.ActiveProducts);
     }
     catch (Exception e)
     {
         UI.DisplayGeneralError(e.Message);
     }
 }