Maybe my brain is not working properly and i cant see the forest because of the trees ...

Currently I have a class called CheckManager which searches the current assembly for a certain type called UserControlBaseCheck which is declared in a separate library. (this works fine)

I do have a variable AllChecks of type SortedDictionary<IBaseCheck, UserControlBaseCheck> (and a custom IComparer class which know's how to sort IBaseCheck).

This variable AllChecks is used to populate a Stack. The stack is then worked through by a User, once it is depleted, it get's filled again with new instances of all classes inside the AllChecks variable. And the whole game starts again.

Currently i solved it this way:

//declaration of my container with all checks
private static SortedDictionary<IBaseCheck, UserControlBaseCheck> AllChecks =
        new SortedDictionary<IBaseCheck, UserControlBaseCheck>(new Comparer());

// this is how i call the method to find all classes which inherit from the type
FindDerivedTypes(Assembly.GetExecutingAssembly(), typeof(UserControlBaseCheck));

//this is the definition... it seems to me bit odd that I have to use the Activator 
//and create an instance and cast it to the interface just to do 
//what i want to do... 
//is there any other / easier / better way of doing so?
public static IList<IBaseCheck> FindDerivedTypes(Assembly assembly,Type baseType)
{
      //FYI: until the '.Select' I get a list of type List<System.Type>
      List<IBaseCheck> o = assembly.GetTypes()
        .Where(t => t != baseType && baseType.IsAssignableFrom(t))
        .Select(type => Activator.CreateInstance(type) as IBaseCheck)
        .ToList();

      return o;
}

i find it odd that I have to create first an instance of the type just to use/convert it to an interface. Why can't i just do: .Select(x=> x as IBaseCheck) I mean i have already a list with object of type List<System.Type> and it seems to me bit overkill what i am doing just to get my list of type IBaseCheck (List<IBaseCheck>)