How to check an "Object"?

I have a DataLayer in my application. The signature in each function returns either a DataSet, DataTable or Integer. However, in the error handling portion, I capture the exception message but I can't return the exception because it's in a string format. If I change the signature to return "Object", which should cover any return value, how do I check "Object" in the calling routine to see if it's a DataSet/DataTable, Integer or a String?

Thanks,