Autofac注册多个接口层次结构，多个具体类

Question

i don't seem to find an answer for my kind of problem. So, let's say have an interface

public interface IBase {        
void MethodBase();    
}

and a class implementing this, BaseClass not abstract). Now i must have another class that should implement the base interface but also to add new methods (extending the default behaviour), so i'm making my second interface like this

public interface IChild : IBase {        
void MethodChild();    
}

and a class that implements this one, say ChildClass.

All good for now. Now the problem with IoC and Autofac. I want, on application start up, to conditionally register as IBase (because the project allready uses IBase in other parts) the first or the second concrete class.

The question is, in a consuming class, in its constructor, should i have a parameter of type IBase and in one of its methods should i do

(baseTypeParam as IChild)

and use one of the new methods added by IChild interface? Because if the constructor parameter is of type IChild and as i said, i register IBase with ChildClass then everything fails because, obviously, there is no IChild registered.

Or i am missing something about how to extend (design pattern?) the base interface with new methods, that the BaseClass should not implement.

Answer 1

You can't cast a parent to a child as you don't know that the implementation you are referencing by IBase actually implements IChild methods. If your class requires methods defined in IChild, it should ask for IChild.

A cleaner solution would to have two implementations of IBase, and not have IChild inherit from IBase. Then you can register which ever implementation of IBase you want depending on your start up parameter, have have a separate class implement IChild.

public interface IBase {        
void DoSomething();    
}

public class Base1 : IBase{
public void DoSomething() { \\do something } 
}

public class Base2 : IBase{
public void DoSomething() { \\do something } 
}

public interface IChild{
void DoSomethingElse();
}

public class Child1{
public void DoSomethingElse() { \\do something else }
}

public class IDoSomething{
public IDoSomething(IBase base){}
}

public class IDoMoreThings{
public IDoMoreThings(IBase base, IChild child){}
}

I understand that it might have made sense for IChild to inherit from IBase but without more context I can't really say.

Hope I understood you question correctly.