You can use Type.GetGenericArguments
to solve this
ClassOfKb kb=new ClassOfKb();
kb.KbData = new List<Data>();
string nameOfData = Type.GetType(kb.KbData.ToString()).GetGenericArguments().Single().Name;
OUTPUT : nameOfData = Data
kb.KbProduct = new List<Product>();
string nameOfProduct = Type.GetType(kb.KbProduct.ToString()).GetGenericArguments().Single().Name;
OUTPUT : nameOfProduct = Product