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 through the factory).

My problem is that CreateInstance fails with a ‘No parameterless constructor defined for this object’ error unless I pass ‘true’ on the non-public parameter.

Example

// Fails Activator.CreateInstance(type);  // Works Activator.CreateInstance(type, true); 

I wanted to make the factory generic to make it a little simpler, like this:

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

However, I was unable to find how to pass that ‘true’ parameter for it to accept non-public constructors (internal).

Did I miss something or it isn’t possible?

Answer 1

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.