Is this for a windows app or a web app? It makes a big difference because most people will not allow Office to be installed on a live webserver. The solution posted above requires Office to be installed on the machine that executes the code. It actually instantiates an Excel application (which can really difficult to kill the thread).

Using the OWC toolset is much cleaner in this case. I can post some sample code for doing this. It will take in a dataset and generate a new excel worksheet for each table in the dataset and then stream it to the request object as an attachment. And no COM objects!!!