Aes a = new Aes(the key size, the seed key);
a.Cipher(plainText, cipherText);
which would be the content to be encrypted and the user supplied password. The arguments for the constructor are explained in the article but I haven't gone that deep yet...
The issue I see with your examples is that the developer would be able to use the keys to decrypt the data as the developer would have created them. In my solution it is vital that the developer would be able to decrypt the data. The data should only be decrypted by the end user it belongs to.
Thanks,
Rit