private static Expression <Func <Patient, bool> > AgeExpression(ushort?yearOfBirth)
{
return(patient => !yearOfBirth.HasValue ||
(patient.YearOfBirth.HasValue &&
AgeGroupMatcher.IsMatching(AgeCalculator.From(yearOfBirth.Value),
AgeCalculator.From(patient.YearOfBirth.Value))));
}