How to sort ArrayList of DateTime objects in descending order?

Question

How do I sort ArrayList of DateTime objects in descending order?

Thank you.

Answer 1

First of all, unless you are stuck with using framework 1.1, you should not be using an ArrayList at all. You should use a strongly typed generic List<DateTime> instead.

For custom sorting there is an overload of the Sort method that takes a comparer. By reversing the regular comparison you get a sort in descending order:

list.Sort(delegate(DateTime x, DateTime y){ return y.CompareTo(x); });

Update:

With lambda expressions in C# 3, the delegate is easier to create:

list.Sort((x, y) => y.CompareTo(x));

Answer 2

As "Guffa" already said, you shouldn't be using ArrayList unless you are in .NET 1.1; here's a simpler List<DateTime> example, though:

List<DateTime> dates = ... // init and fill
dates.Sort();
dates.Reverse();

Your dates are now sorted in descending order.