Hashtable Question

Question

I am trying to find a solution on how to do a specific task.. Currently i have many instances of a particular class with its own private Hashtable, this Hashtable is indexed by an integer and a stores a DateTime at each of these indexed integers. I wish to save this Hashtable using a binary formatter, which i have no problem doing. However, currently, i am creating a seperate file for each and every instance of my Hashtable, how could i create a file that stores them all? and then lets me reference them to load them back and restore my Hashtable info to each instance of my class? Many thanks for reading.. Jay