setting datetime to null

Question

I have two DateTime variables first period and second period and with each period i have a date range between two date for each period. My issue is that i usually set my dates to null withn i load the page but for these dates i cannot set them to null which i would like rather than setting a specific date.

DateTime firstPeriodBeginDate = DateTime.Today.AddMonths(-3);
DateTime secondPeriodBeginDate = DateTime.Today.AddMonths(-2);

I would like it set to null so that it will equal to the values selected from the date picker by the user when used to render results.

Solution 1

DateTime is a non-nullable value type, so cannot be null.

You can use a Nullable<DateTime> for such a thing:

DateTime? firstPeriodBeginDate = DateTime.Today.AddMonths(-3);
DateTime? secondPeriodBeginDate = null;

Solution 2

The DateTime structure cant be null.

But you can use a nullable DateTime

DateTime? dateTime;
dateTime = null;

and check for null

if (dateTime.HasValue)

More information: C# Nullable DateTime

hope this helps

Comments

[Jon Skeet]

It's probably worth editing the first part to "DateTime is a non-nullable value type, so cannot be null." After all, Nullable<DateTime> is a value type, too...

[Masriyah]

I tried this but my issue in my repository and services i am using a daterange and i am not sure of how to set that to null. I tried setting my date times to null but then i get errors when i build saying i cannot convert date range to null.

[Oded]

@Amina - Well, how can there be a range between dates if one of the dates is null?

[Masriyah]

when setting to DateTime.MinDate does that defult to the min value and pass it as a value to render results? I mean if my min value would be 1/1/0001 and it will render results based on that date and then will it change to whatever i choose from the date picker? Thanks

[Masriyah]

first date = 01/20/2010 - 02/20/2010 second date = 02/20/2010 - 03/20/2010 for each of the dates i have a date range which could be a week, month, quarterly, or yearly and then i use a date time.

[dknaack]

Sorry, not really clear what you mean. Could you explain it please. thank you

[Masriyah]

Get(DateRange firstPeriodDateRange, DateRange secondPeriodDateRange, int? officeId) { return DataContext.Report_ResultsData(firstPeriodDateRange.DateStar‌​t, firstPeriodDateRange.DateEnd, secondPeriodDateRange.DateStart, secondPeriodDateRange.DateEnd, officeId).AsQueryable(); }

[Oded]

@Amina - I don't understand. Perhaps post a new question, referencing this one.

[Bengie]

To go along with this: DateTime is a struct(value), so it can't be null. You have to box the struct into an object, which adds overhead any time you access it, but it'll do your job of being null. Another way is to have a default value that one can treat as null, like DateTime.Min, since one would have to check for null before comparing anyway.