SelectRandom.cs

//Apply selector to a random subset of source of size count and return the results
public static class ExtensionHelpers {
    public static IEnumerable<TOut> SelectRandom<TSource, TOut>(this IEnumerable<TSource> source,
                                                                Func<TSource, TOut> selector,
                                                                int count) {
        var rand = new Random((int) (DateTime.Now.Ticks % int.MaxValue));
        for (var i = 0; i < count; i++)
            yield return selector(source.ElementAt(rand.Next(source.Count())));
    }
}

//Basic examples
var randomNames = listOfPeople.SelectRandom(person => person.Name, 10);
var randomData = listOfIds.SelectRandom(id => data.GetDataForId(id), 20);