System.DateTime? vs System.DateTime

Question

I was writing to some code where I needed to read the date value from a Calendar control in my page (Ajax toolkit: calendar extender).

The code below:

Answer 1

DateTime? is the same as Nullable That is: an instance of DateTime? can contain 'NULL', whereas an instance of DateTime does not. (This is true for all value - types since .NET 2.0. A Value type cannot contain NULL , but, as from .NET 2.0, nullable value types are supported via the Nullable construct (or the ? shorthand).

You can get the value of DateTime? and put it in DateTime by doing this:

DateTime? someNullableDate;
DateTime myDate;

if( someNullableDate.HasValue )
   myDate = someNullableDate.Value;

Another, conciser way to get the value of a Nullable, is by using the null-coalescing operator:

DateTime myDate = someNullableDate?? default(DateTime);