Sorting of data in specific format

I have tried to edit my code to the following But dont seem to be the correct way:

public int Compare(object x, object y)
{
    string s1 = (string)x;
    string s2 = (string)y;

    return DateTime.Compare(DateTime.ParseExact(s1.Substri开发者_C百科ng(1), "MMddyyyy", CultureInfo.InvariantCulture),
                            DateTime.ParseExact(s2.Substring(1), "MMddyyyy", CultureInfo.InvariantCulture));
}

protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
{
    IsolatedStorageFile myStore = IsolatedStorageFile.GetUserStoreForApplication();

    if (scheduleListBox.Items.Count == 0)
    {
        try
        {
            //Get all the directories name that start with "a"
            fileNames = myStore.GetDirectoryNames("a*");
            //Sort according to the schedule month
            //Array.Sort(fileNames);
            Array.Sort(new Compare(fileNames));

I have a data in a format of a08102011 in a array list.

Where 08 is the month, 10 is the day, 2011 is the year.

How can it be sorted in the way that?

a08102011

a09112011

---

Sorting an ArrayList with custom string:

Assuming your string format is using fixed width fields (always one character prefix, always two characters for days etc.) you could use a custom IComparer implementation:

public class CustomComparer : IComparer
{
    public int Compare(object x, object y)
    {
        string s1 = (string) x;
        string s2 = (string) y;

        return DateTime.Compare(DateTime.ParseExact(s1.Substring(1), "MMddyyyy", CultureInfo.InvariantCulture), 
                                DateTime.ParseExact(s2.Substring(1), "MMddyyyy", CultureInfo.InvariantCulture));
    }
}

..
ArrayList items = new ArrayList();
items.Add("a08102011");
items.Add("a09112011");

items.Sort(new CustomComparer());

Of course there is no real reason you should have to use an ArrayList in the first place - use a strongly typed collection like List<string> instead - the same concept applies there, just use an IComparer<string> custom implementation.

Update: Strongly typed IComparer

It looks like you really are using a string array, not ArrayList, so use the strongly typed version of the CustomComparer:

public class CustomComparer : IComparer<string>
{
    public int Compare(string  x, string y)
    {
        string s1 = (string) x;
        string s2 = (string) y;

        return DateTime.Compare(DateTime.ParseExact(s1.Substring(1), "MMddyyyy", CultureInfo.InvariantCulture), 
                                DateTime.ParseExact(s2.Substring(1), "MMddyyyy", CultureInfo.InvariantCulture));
    }
}

Then you can sort your array like this:

string[] items = new string[] { "a09112011", "a08102011" };
Array.Sort(items, new CustomComparer());

Finally: The Linq approach

Also, much shorter, you can use Linq instead - which does create a new sorted array though, so it's a little more compute intensive but that should not matter in the overall scheme of things:

string[] items = new string[] { "a09112011", "a08102011" };
items = items.OrderBy(x => DateTime.ParseExact(x.Substring(1), 
                                               "MMddyyyy", 
                                               CultureInfo.InvariantCulture))
             .ToArray();