Create trigger to encrypt column and fetch it to code behind and than decrypt it in c#

I have following table .
Table Name - ConnectionTable Id pk user int connectionString nvarchar so when user insert data manually(there is no UI to insert data in this table so admin user insert data manually) in this table ,column "connectionString" should be encrypted.
And i fetch this column in my c# code (at server side) at that time i want to decrypt it.