Question

I have the following code example:

    List<int> list = new List<int>();

    list.Add(1);
    list.Add(2);
    list.Add(3);
    list.Add(4);
    list.Add(5);
    list.Add(6);
    list.Add(7);

  list.OrderByDescending(n=>n).Reverse();

But when I use this:

list.OrderByDescending(n=>n).Reverse();

I don’t get wanted result.

If instead of the above statement, I use this one:

list.Reverse();

I get the wanted result.

Any idea why I don’t get wanted result using the first statement ?

I believe I am missing something in understanding the extensions.

Thank you in advance.

Answer 1

Edit: So the problem seems to be that you think that the Enumerable extensions would change the original collection. No they do not. Actually they return something new you need to asign to a variable:

IEnumerable<int> ordered = list.OrderByDescending(n => n);
foreach(int i in ordered)
    Console.WriteLine(i);

---

OrderByDescending orders descending(highest first) which is what you obviously want. So i don’t understand why you reverse it afterwards.

So this should give you the expected result:

var ordered = list.OrderByDescending(n=> n);

This returns an “arbitrary” order:

list.Reverse()

since it just reverses the order you have added the ints. If you have added them in an ordered way you don’t need to order at all.

In general: use OrderBy or OrderByDescending if you want to order a sequence and Reverse if you want to invert the sequence what is not necessarily an order (it is at least confusing).