private string Round(FormatNumberTO formatNumberTO)
// ReSharper restore InconsistentNaming
{
string error;
string result;
_functionEvaluator.TryEvaluateFunction(BuildRoundingExpression(formatNumberTO), out result, out error);
if(!string.IsNullOrWhiteSpace(error))
{
throw new InvalidOperationException(error);
}
return result;
}