IoC解决非引用依赖性

interface IFoo { }
class FooA : IFoo { }
class FooB : IFoo { }

//not a builder. generates based on conditions
interface IFooEmitter<TFoo> 
{
    TFoo EmitFoo(); 
} 

abstract class FooEmitterBase<TFoo> : IFooEmitter<TFoo> { }

class FooAEmitter : FooEmitterBase<FooA> { }

[RequiresEmitter(typeof(FooAEmitter))]
class FooBEmitter : FooEmitterBase<FooB> { }

var b = FooEmitterManager.CreateAndStore<FooBEmitter>(); 

//continued from above
var a = FooEmitterManager.CreateAndStore<FooAEmitter>();
Debug.Assert(a == b); // true