Question

I’m trying to get datetime value but here is issue with nullable datetype. How to fix that?

Public Function GetDate(ByVal kodg As Integer) As DateTime
    Dim g = From dt In db.xDates _
            Join f In db.xGrafiks On dt.КодД Equals f.DateKod _
            Where f.Kod = kodg
            Select New Date?(dt.Дата) ???
    Return g ???
End Function

Answer 1

g will be a IQueryable(Date?), which is a collection, so you first have to check if there is a value. You can do this by using FirstOrDefault() (if there can be multiple results or none), or SingleOrDefault (if there shouldn’t be multiple resulst).

Then you get one Date? back. You can then use the HasValue property to check if the Date? has a value, if that’s true just return it. If not you should return another Date from your function (maybe DateTime.MinValue ?).

Or you could change the return value of your function to be a Date? and the just return the nullable date from your query.