Activator.CreateInstance(string) and Activator.CreateInstance() difference

Question

No, this is not a question about generics.

I have a Factory pattern with several classes with internal constructors (I don\'t want them being instantiated if not thr

Answer 1

besides Activator.CreateInstance(typeof(T), true) to work, T should have default constructor

Answer 2

To get around this, couldnt you just alter your usage as such:

public class GenericFactory<T> where T : MyAbstractType
{
    public static T GetInstance()
    {
        return Activator.CreateInstance(typeof(T), true);
    }
}

Your factory method will still be generic, but the call to the activator will not use the generic overload. But you should still achieve the same results.

Answer 3

If you absolutely require that the constructor be private you can try something like this:

public abstract class GenericFactory<T> where T : MyAbstractType
{
    public static T GetInstance()
    {
        return (T)Activator.CreateInstance(typeof(T), true);
    }
}

Otherwise you're best off adding the new constraint and going that route:

public abstract class GenericFactory<T> where T : MyAbstractType, new()
{
    public static T GetInstance()
    {
        return new T;
    }
}

You're trying to use GenericFactory as a base class for all of your factories rather than writing each from scratch right?