Question

I have a WPF client that retrieves data using a DateTime from a WCF service.

When I put my computer on Rome time (+1) I see some strange behaviour with my results.

My WCF Method

        public IEnumerable<BookingType> BookingsForFollowingDayReport(DateTime date) {

        el = new ErrorLogging();
        el.CreateLog(db, new Entities.ErrorType() { DateLogged = DateTime.Now, Type = "DTE", Message = "Report Date: " + date.ToString() });

        var a = (from b in db.GetTable<BookingType>()
                 where b.TourStartDateTime >= date.Date && b.TourStartDateTime <= date.AddDays(1).Date
                 orderby b.TourStartDateTime
                 select b);

        if (a.Count() > 0) {
            el.CreateLog(db, new Entities.ErrorType() { DateLogged = DateTime.Now, Type = "DTE", Message = "Report Date: " + a.FirstOrDefault().TourStartDateTime });
        }

        return a;
    }

The service is online on some web server somewhere and now I call it from my WPF client. Note the logging I have inside my method.

My Calling Code

    public static async Task<Bookings> GetBookingsReport(DateTime forWhen) {
        Bookings bookings = new Bookings();
        if (MyNetwork.IsOnline) {
            var bookingTypes = new ReportsServiceClient.BookingType[0];

                //forWhen = new DateTime(2013, 01, 10);
                bookingTypes = await ReportsServiceClient.BookingsForFollowingDayReportAsync(forWhen);


            bookings.TourBookings = (from b in bookingTypes
                                     where b.RecordType == "H"
                                     select new Booking(b)).ToList();

        }
        return bookings;
    }

Now for the strangities…

I call the ‘calling code’ from a XAML code behind using a DatePicker‘s value like so: await DataManager.GetBookingsReport(datePicked.SelectedDate.Value); and I’ll
debug through the code to the point where BookingsForFollowingDayReportAsync is called.

The variable forWhen is actually the 10/01/2013, great! ..accept my logging code in WCF service says 09/01/2013 is sent through. So then I uncomment the line where I set forWhen manually – just to test – and it works, the logger says 10/01/2013.

I’ve tested this over a few days now and it always has a problem with tomorrows date, if I pick three days away (past or future) in my DatePicker for example the correct date is logged.

If I set my timezone back to UK GMT time, this bug does not happen at all as well.

I’ve got an idea it might be something to do with the date picker since setting forWhen manually removes the problem, but how can this be happening?

Edit 1
I’ve managed to solve the problem for now, by setting forWhen manually, using forWhens Values like so (as nonsensical as it looks):

forWhen = new DateTime(forWhen.Year, forWhen.Month, forWhen.Day);

I’m perplexed by the problem and the solution I’ve found to it… Any explanations?

Answer 1

By default, WCF serializes and deserializes DateTime objects based on the local time zone. This means the DateTime from the client gets decremented on the server by one hour when it is deserialized in your case. Apparently your time portion is 0 (midnight), so that would explain yesterday’s date.

One of the solutions is to explicitly set DateTime.Kind to DateTimeKind.Unspecified before you pass the DateTime variable to the service like so:

DateTime forWhenSvcArg = DateTime.SpecifyKind(forWhen, DateTimeKind.Unspecified);

That’s what you get when you set forWhen by means of calling the constructor also.