url encode a tripleDES encrypted string

I am using TripleDES to encrypt some querystring parameters. However, I have found that tripleDES includes some characters ("/" for instance) that mess up the querystring. I tried using Server.URLEncode to encode the encrypted string and then UrlDecode before Decrypting, however URLEncode doesn't seem to encode slashes. I can, of course, do a simple replace, however I am concerned that I don't know all the potential problematic characters that might appear in a TripleDES encrypted string. Is there some built in funciton that can be used to ensure a string is URLEncoded for querystring puposes, including slashes?
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