double? fixedPriceDouble = double.TryParse(fixedPrice, out double converted) ? converted : null;

Converts a String variable of fixedPrice into a double? called fixedPriceDouble.

double? fixedPriceDouble = double.TryParse(fixedPrice, out double converted) ? converted : null;

Converts a String variable of fixedPrice into a double? called fixedPriceDouble.