Sorting an array of folder names like Windows Explorer (Numerically and Alphabetically) - VB.NET

Question

I'm killing myself and dehydrating trying to get this array to sort.

I have an array containing directories generated by;

Dim Folders() As String = Directory.GetDirectories(RootPath)

I need them to be sorted so they appear like in Windows Explorer in win7 / Vista. -- numerically and alphabetically by folder names.

The folder names contain both letters and numbers, sometimes letters only or numbers only.

The simple Array.Sort(Folders) results in

C:\inetpub\wwwroot\rootpath\1
C:\inetpub\wwwroot\rootpath\10
C:\inetpub\wwwroot\rootpath\100
C:\inetpub\wwwroot\rootpath\1004
C:\inetpub\wwwroot\rootpath\101
C:\inetpub\wwwroot\rootpath\11
C:\inetpub\wwwroot\rootpath\12
C:\inetpub\wwwroot\rootpath\2
C:\inetpub\wwwroot\rootpath\3
C:\inetpub\wwwroot\rootpath\4
C:\inetpub\wwwroot\rootpath\5
C:\inetpub\wwwroot\rootpath\6
C:\inetpub\wwwroot\rootpath\7
C:\inetpub\wwwroot\rootpath\8
C:\inetpub\wwwroot\rootpath\87skjnd
C:\inetpub\wwwroot\rootpath\89sdf93kmw3
C:\inetpub\wwwroot\rootpath\9
C:\inetpub\wwwroot\rootpath\ad
C:\inetpub\wwwroot\rootpath\bin
C:\inetpub\wwwroot\rootpath\dark
C:\inetpub\wwwroot\rootpath\erk
C:\inetpub\wwwroot\rootpath\jkh23978yoaslkd3
C:\inetpub\wwwroot\rootpath\lk2309as
C:\inetpub\wwwroot\rootpath\work
C:\inetpub\wwwroot\rootpath\zone

What I want to have (and what Windows Explorer displays) is ...

C:\inetpub\wwwroot\rootpath\1
C:\inetpub\wwwroot\rootpath\2
C:\inetpub\wwwroot\rootpath\3
C:\inetpub\wwwroot\rootpath\4
C:\inetpub\wwwroot\rootpath\5
C:\inetpub\wwwroot\rootpath\6
C:\inetpub\wwwroot\rootpath\7
C:\inetpub\wwwroot\rootpath\8
C:\inetpub\wwwroot\rootpath\9
C:\inetpub\wwwroot\rootpath\10
C:\inetpub\wwwroot\rootpath\11
C:\inetpub\wwwroot\rootpath\12
C:\inetpub\wwwroot\rootpath\87skjnd
C:\inetpub\wwwroot\rootpath\89sdf93kmw3
C:\inetpub\wwwroot\rootpath\100
C:\inetpub\wwwroot\rootpath\101
C:\inetpub\wwwroot\rootpath\1004
C:\inetpub\wwwroot\rootpath\ad
C:\inetpub\wwwroot\rootpath\bin
C:\inetpub\wwwroot\rootpath\dark
C:\inetpub\wwwroot\rootpath\erk
C:\inetpub\wwwroot\rootpath\jkh23978yoaslkd3
C:\inetpub\wwwroot\rootpath\lk2309as
C:\inetpub\wwwroot\rootpath\work
C:\inetpub\wwwroot\rootpath\zone

I googled and found out that a class needs to be written that uses IComparable to sort the elements. Being a super newbie... I really don't know how it can be done. Most examples I looked at had multi-dimensional arrays and keys :S ...

would be even nicer if the sorting could be applied to an array of filenames (instead of folder names) or an array containing both folders and files ... in which case the sorted folders appear at the top and sorted files below ... is this even possible?

Any help will be greatly appreciated... :D thanks.

Answer 1

You would need to implement an IComparer, as opposed to creating a class that implements IComparable. The difference is that an IComparer has the necessary "knowledge" to compare two objects whereas IComparable is implemented by a class that knows how to compare itself against something else.

And the way Windows Explorer sorts filenames is using a function called StrCmpLogicalW. You can use this function in your own IComparer to get the same sort behavior as Windows Explorer. This function treats numeric parts of strings as numbers so that 9 sorts before 10.

public class MyComparer : IComparer<string> {

    [DllImport("shlwapi.dll", CharSet=CharSet.Unicode, ExactSpelling=true)]
    static extern int StrCmpLogicalW(String x, String y);

    public int Compare(string x, string y) {
        return StrCmpLogicalW(x, y);
    }

}

Array.Sort(unsortedNames, new MyComparer());

And since I just noticed the question is tagged VB... Forgive my rusty VB!

Public Class MyComparer
    Implements IComparer(Of String)

    Declare Unicode Function StrCmpLogicalW Lib "shlwapi.dll" ( _
        ByVal s1 As String, _
        ByVal s2 As String) As Int32

    Public Function Compare(Byval x as String, Byval y as String) As Integer _
        Implements System.Collections.Generic.IComparer(Of String).Compare

        Return StrCmpLogicalW(x, y)

    End Function

End Class