var persons = new[]
{
new {Id = 1, Name = "Foo"},
new {Id = 2, Name = "Bar"},
new {Id = 3, Name = "Fizz"},
new {Id = 4, Name = "Buzz"}
};
var personsSortedByNameDescending = persons.OrderByDescending(p => p.Name);
Console.WriteLine(string.Join(",", personsSortedByNameDescending.Select(p => p.Id).ToArray()));
//1,3,4,2