Sep 02, 2012 10:11 PM|Decker Dong - MSFT|LINK
I get something like DateTime UserCreated cannot be null.
Of course it cannot be null——as I said, DateTime and any struct type cannot be assigned or compared with null.
But if you insist doing so, please use Nullable<DateTime> instead of DateTime.
All in all, you should create the instance of the class to set the default value.