.NET 4.0 Calendar control member SelectedDate is of type "DateTime?" ?

Question

In .NET 4.0 if you create a Calendar and you look at the SelectedDate field it is of type "DateTime?". What's the deal with the ? at the end of the type?

Answer 1

? at the end means it's nullable, as in, the control may not have a SelectedDate at all.

See: http://msdn.microsoft.com/en-us/library/1t3y8s4s.aspx

Answer 2

? at the end means that a value type can also be null.

Answer 3

DateTime? means Nullable<DateTime> that's meaning that this property can hold null. Meanwhile just DateTime - cannot.

See more about Nullable Types on MSDN