Is it possible to instantiate a parameterized Generic

Yes it is possible, but firstly you should remove the new() constraint on the method signature.

1. Create the abstract class.

    public abstract class AbstractOU
    {
        public AbstractOU(int id, DateTime dt)
        {

        }

    }

2. Create the derived class:

    public class OU : AbstractOU
    {
        public OU (int a, DateTime b) : base(a,b){}
    }

3. Create your method which looks like this:

        private T GetOU() where T:AbstractOU
        {
            //return new T(100, DateTime.Now);
            //Type type = Type.GetType(T);
            T ret = (T) Activator.CreateInstance(typeof(T), new object[] { 100, DateTime.Now });
            return ret;
        }

If you add the new() constraint on the method signature above, the c# compiler would require a parameterized default constructor on the class definition when you call the method by :

AbstractOU a = GetOU();

Hope this helps!