http://arcanecode.com/2007/03/21/encoding-strings-to-base64-in-c/ static public string EncodeTo64(string toEncode) { byte[] toEncodeAsBytes = System.Text.ASCIIEncoding.ASCII.GetBytes(toEncode); string returnValue = System.Convert.ToBase64String(toEncodeAsBytes); return returnValue; } Note two things, first I am using ASCII encoding, which should cover most folks. Just in case though, System.Text..