Up until now there has been a problem to filter on type in Linq

The problem can be shown with this model:

If you want to find SomeSubClass that has a Class2 with a specific name :

var foo2 = (from v in EcoLinqExtender.PSQuery<Class2>(EcoSpace) 
     where (v.Class1.Attribute1 == "5" && v.Name == "5A") 
         select v.Class1)

But now you also get Class1’s that are not of SomeSubClass. And that is a problem in certain situations.

In Ocl2Ps we would have done:

Class2.allInstances->select(a|((a.Class1.Attribute1 = '5') and (a.Name = '5A'))).Class1->FilterOnType(SomeSubClass)

Until now MDriven Linq2Sql logic did not understand the Linq counterpart of FilterOnType – which is OfType<class>().

But now it does:

var foo2 = (from v in EcoLinqExtender.PSQuery<Class2>(EcoSpace) 
       where (v.Class1.Attribute1 == "5" && v.Name == "5A") 
           select v.Class1).OfType<SomeSubClass>()

With this is place the database takes care of all the filtering for us and returns the SomeSubClasses that has any Class2 with the correct criteria.