NHibernate possible bug in IQuery.List()

Emad Alashi — Sun, 21 Sep 2008 22:09:15 +0000

recently, we had to clean the database from all the testing data, when an error similar to the following appeared:

The value “” is not of type “System.Nullable`1[System.DateTime]” and cannot be used in this generic collection

The code I executed was:

            IQuery query = DbManager.MySession.CreateQuery(“select max(dateObject.EndDate) from DateDomain dateObject”);
            IList<DateTime?> list = query.List<DateTime?>();

When I debugged NHibernate code, I reached to the following AddAll() method in the ArrayHelper class:

  152 // NH-specific
  153         public static void AddAll(IList to, IList from)
  154         {
  155             foreach (object obj in from)
  156             {
  157                 to.Add(obj);
  158             }
  159         }

You can find the explanation of the error here.
Which brings us to the interesting question: why the implementation of IList Add method doesn’t consider the “nullability” of the T object? and why the parameter is of type IList ?!

Am I missing something? should I report it as a bug?

Emad Alashi's Blog » NHibernate IQuery bug IList

NHibernate possible bug in IQuery.List()