Find TotalDays between two Datetime? variables

Question

   DateTime? arrival = (DateTime?)(t.ArrivalDate.Value);
   DateTime? departure = (DateTime?)(t.DepartureDate);

Okay i know both of them are nullable and .TotalDays does not work on nullable object. So kindly tell me how am i supposed to find days difference between these two objects.

Note: Both objects contains Date(s) i.e. are not null

Answer 1

Since there's no meaningful value to their difference if any of them is null, you only need to concern yourself with the case where they're not:

DateTime? arrival = (DateTime?)(t.ArrivalDate.Value);
DateTime? departure = (DateTime?)(t.DepartureDate);
double? totalDays = arrival.HasValue && departure.HasValue 
   ? (double?)(departure - arrival).GetValueOrDefault().TotalDays
   : null;

The subtraction should work because of implicit casting to DateTime.