The following returns
Type of conditional expression cannot be determined because there is no implicit conversion between 'double' and '<null>'
aNullableDouble = (double.TryParse(aString, out aDouble)?aDouble:null)
The reason why I can't just use aNullableBool instead of the roundtrip with aDouble is because aNullableDouble is a property of a generated EntityFramework class which cannot be used as an out par.