Now what you are trying to do is create an object of a class which does not exist on the PC and so it should not be done the way you are doing it. The way it should be done is as follows.
Create your own wrapper dll for FoxItReader.dll and I would call it MyFoxItReader.dll which does all the needed object initialization and variable declaration.
Then in your app you do the checking if you have the needed DLL extension
If yes then you load your own dll ( MyFoxItReader.dll )
I hope you got what I meant.