The below HELP File info says not to use the UDL files: Cecil
Do Not Use Universal Data Link Files
It is possible to supply connection information for an OleDbConnection in a Universal Data Link (UDL) file; however you should avoid doing so. UDL files are not encrypted, and expose connection string information in clear text. Because a UDL file is an external file-based resource to your application, it cannot be secured using the .NET Framework.
Storing Connection Strings in Configuration Files
To avoid storing connection strings in your code, you can store them in the web.config file for an ASP.NET application and in the app.config file for a Windows application.
The connection string can be stored in the configuration file in the
element. Connection strings are stored as key/value pairs, where the name can be used to look up the value stored in the connectionString attribute at run time. The following example of a configuration file shows a connection string named DatabaseConnection which references a connection string that connects to a local instance of SQL Server.
