The string from the web service is "599.00". If I Convert.ToDecimal(theString) I still get 599.00,00 when displayed in the datagrid output.
If the string from the web service always uses a dot as decimal separator, convert using the InvariantCulture, which has a .
as DecimalSeparator
:
decimal amount = Convert.ToDecimal("559.00", CultureInfo.InvariantCulture);