Can anyone explain to me, at length, how to use IOC containers?

Question

I use dependency injection through parameters and constructors extensively. I understand the principle to this degree and am happy with it. On my large projects, I end up with t

Answer 1

If you have over a hundred of classes implementing a common interface, an IoC won't help very much, you need a factory. That way, you may do the following:

public interface IMyInterface{
    //...
}

public class Factory{

    public static IMyInterface GetObject(string param){
        // param is a parameter that will help the Factory decide what object to return
        // (that is only an example, there may not be any parameter at all)
    }
}

//...
// You do not depend on a particular implementation here
IMyInterface obj = Factory.GetObject("some param");

Inside the factory, you may use an IoC Container to retrieve the objects if you like, but you'll have to register each one of the classes that implement the given interface and associate them to some keys (and use those keys as parameters in GetObject() method).

An IoC is particularly useful when you have to retrieve objects that implement different interfaces:

IMyInteface myObject = Container.GetObject();
IMyOtherInterface myOtherObject Container.GetObject();
ISomeOtherInterface someOtherObject = Container.GetObject();

See? Only one object to get several different type objects and no keys (the intefaces themselves are the keys). If you need an object to get several different object, but all implementing the same interface, an IoC won't help you very much.