当我改变一个部分时，我如何让我的大脑重新合成?

I am trying to get MEF to recompose all the parts that it knows about when I update an instance that is exported. Essentially I want to have MEF update all my parts that import a connection string configuration value when it is changed. Everything looks good up to the point where I want to change the instance. If I try to ComposeParts with the value updated it seems to add a second part instance into the container, and then my imports are updated, but to null.I am trying to get MEF to recompose all the par