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Using .Net how do I use the Sort method to sort an Array in reverse i.e. Z to A?

Answer 1

+3 A:

You need to pass a IComparer object or Comparison delegate to the Sort function.

Here is a sample code from C# 2.0

   Array.Sort(array,delegate(string a, string b)
    {
        return b.CompareTo(a);
    });

EDIT: missed the array bit.

Michał Piaskowski 2008-10-30 23:04:14

Why not simply return b.CompareTo(a)?

Chris Marasti-Georg 2008-10-30 23:09:54

Yeah, that's better.

Michał Piaskowski 2008-10-30 23:14:01

There are actually two important differences here:1) What should happen to null strings? Often when reversing comparisons you *don't* want to reverse what happens to nulls. Just a thought. 2) Returning -a.CompareTo(b) (i.e. pre-edit) causes problems if int.MinValue is returned by a.CompareTo(b).

Jon Skeet 2008-10-31 07:16:40

I'm pretty sure most string sorting algorithms, like this one, would throw NullReferenceExceptions if there is a null value in the list. However, the point you bring up in #1 remains for empty strings.

Chris Marasti-Georg 2008-10-31 11:28:03

Answer 2

+11 A:

Provide an appropriate element comparer. What C# version do you use? 3 lets you do this:

Array.Sort(myarray, (a, b) => b.CompareTo(a));

Konrad Rudolph 2008-10-30 23:05:14

Answer 3

+1 A:

if you use a different comparitor that is the reverse of the standard that would do it.

Alternatively sort it normally and then reverse it...

Omar Kooheji 2008-10-30 23:07:56

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Using .Net how do I use the Sort method to sort an Array in reverse i.e. Z to A?

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