به صورت زیر اصلاح کردم درست شد!
public static double StringToDouble(string numberString){
double numberDouble;
if(!double.TryParse(numberString, NumberStyles.Number, CultureInfo.CreateSpecificCulture("en-US"), out numberDouble))
{
double.TryParse(numberString, NumberStyles.Number, CultureInfo.CreateSpecificCulture("fa-IR"), out numberDouble);
}
return numberDouble;
}