Fill DataSet from SQL Database

Hello everyone. Now I'm trying to fill a DataSet from a table in a SQL Database.
Normally I can use the SqlDataAdapter, but now I have other problem.
 
The table is composed by 3 columns ID, UserName, Password.
UserName and Password are Encrypted, so I need to do the next thing:
 
Get all items of the table, decrypt all items from UserName column, and later fill the DataSet with that new data.
 
Can you provide to me some ideas?
 
Thanks