Help with encoding and decoding SMPP PDU packets

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C#

C#4.0

I am currently working on a project that requires me to create a gateway for sending SMS's to an SMSC. I know that in order to send messages to the SMSC, the messages have to be PDU format, like for instance the submit_sm PDU. I would just like to know if there is any good links out there showing me how to generate an SMPP PDU in code, like for instance an class that handles the process of Encoding and decoding PDU? any help would greatly be appreciated.