.net 3.5: To read connectionstring from app.config?

In the config:

<add name="ConnectionName" connectionString="Data Source=xxxx\yyyy;Initial Catalog=MyDB;User ID=userName;Password=pwd" />

In C# code:

    using System.Configuration;

...

    string connectionString = ConfigurationManager.ConnectionStrings["ConnectionName"].ToString();

Better still would be to define a function and use it in the code everywhere:

public string getConnectionStringMyDB()
        {
            return ConfigurationManager.ConnectionStrings["ConnectionName"].ToString();
        }