How can I have a class derived from a class known at runtime implementing an interface known at compilation

Question

I think I'd be easier to just write down my pseudo-class declaration.

Basically, I want something like

public class DatabaseControlsDAL<T> : T, IDatabaseControlsDAL where T : IBaseDAL
{
   public int myMethod()
   {
      return somePublicPropertyInTheIBaseDALInterface;
   }
}

But it won't work :(

Any help welcome !

does your class have a `T` or a list of `T` somewhere in it? — Sam I am says Reinstate Monica, Feb 18 '14 at 22:04
Nope. `T : IBaseDAL` only provides a couple of helper function meant to be overriden in a test environment. — Literal, Feb 18 '14 at 22:05
why do you need to do this? if T is an IBaseDAL, why not just pin that? — devshorts, Feb 18 '14 at 22:06
Well actually the T value is known through dependency injection, but I'd like to have my DAL classes inherit from it, instead of instanciating it. — Literal, Feb 18 '14 at 22:07
Considering the title of your question only, yes. What you are looking for is called "dependency injection" or "inversion of control". There are a lot of libraries that do this. — Larry, Feb 18 '14 at 22:14
It sounds like you need to use "composition" rather than "inheritance". Try going down that path. — Enigmativity, Feb 18 '14 at 22:44
You'd need something like this http://stackoverflow.com/questions/2659728/creating-c-sharp-classes-at-runtime — Benjamin Berry, Feb 18 '14 at 23:53

score 0 · Answer 1 · answered Feb 18 '14 at 22:09

Generics aren't a run-time feature, thus giving a generic argument won't be a run-time issue.

In the other hand, how would a class inherit what will be only known at run-time? Think C# is a strongly-typed language.

If B inherits A, but A is "unknown", then, until run-time, B won't be of type A. This defeats both the point of inheritance and polymorphism.

Conclusion: if you don't provide a background in order to let us define a better solution (well, an existing solution!), you'll get this answer: you can't achieve what you're looking for in C#.

How can I have a class derived from a class known at runtime implementing an interface known at compilation

1 Answers1