Why can't do this in c#????

gbianchi · May 3rd, 2009, 08:20 PM

Hi people..

Unless I lost some brain somewhere, I don't understand why I can't do this..

I have an abstract class (say class1) and a child class (childclass).

I'm loading the dll with the childclass by reflection, calling up the correct class, and trying to instanciate it using a cast to class1.

Code:

Class1 class1 = (Class1) Activator.CreateInstance(childclass)

childclass has the correct type that I need to activate.

This code, throw an error that can't convert childclass to class1. Isn't this possible??? Childclass can't be converted to his base class?? or it's because it is an abstract class??? (the one I'm trying to convert it to??)

Old Pedant · May 3rd, 2009, 11:29 PM

I'm going to play with this, but in the meantime...

Why not write a little debugging code?

Code:

Object o = Activator.CreateInstance(childclass);
Reponse.Write( o.ToString() + "<hr>" + o.GetType() ); // or use console output

Old Pedant · May 3rd, 2009, 11:31 PM

Oh, never mind...you said the error is "can't convert childclass to class1", so that means that the CreateInstance *did* properly return a childclass instance, as you would expect.

So if that code fails, then why wouldn't

Code:

childclass c = new childclass( );
Class1 c1 = (Class1) c;

*also* fail??

gbianchi · May 4th, 2009, 08:17 AM

Lol... There is an underlying problem with childclass. The contructor is throwing an exception.. I don't see any reference to it in my side, and c# still build the class (?), but the problem is there. I will try to solve it an come back. Your second idea worked for me to see the error. :)

gbianchi · May 4th, 2009, 10:06 AM

Ok, I think I found out the problem.

The cast is valid if I have the two classes referenced on my solution.

since I'm loading one of them using reflection, the create instance returns a class of type object, that doesn't have inherits info on it. So I believe it can't do the cast because it does not have info on how to cast it.

So I have a new question. Any one know if it is posible to do the cast in any way??? I want to avoid using invoke (because I know what I need to invoke).