Google is your friend: Be nice and visit him often. He can answer questions a lot more quickly than posting them here...
A very quick search gave over a million hits:
Encrypt and Decrypt Data using in symmetric[
^]
As expected, MSDN is high on the list:
Encrypting and Decrypting Data[
^]
In future, please try to do at least basic research yourself, and not waste your time or ours.
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