Sort directory path alphabetically - vb.net

Question

Below code is used for sorting Directories in vb.net.
Dim a As New List(Of String)
a.Add("a\b\c")
a.Add("a\b\c\d")
a.Add("a\b\c d")
a.Add("a\b\c d\e")
a.Add("a\b\c\d\f")
a.Sort(Function(x, Y) (x).CompareTo((Y)))
result:
a\b\c
a\b\c d
a\b\c d\e
a\b\c\d
a\b\c\d\f
In the result list directories with space is placed before "\".
There are more than 1500000 sub-directories and files
it takes around 50 seconds to sort(default method)
all other methods we tried is taking at least 400 seconds.
how to sort directory path alphabetically?
Is there any built in method to consider Backslash before space ?

Answer 1

You need to break the path up into individual folder names and compare each of them in turn until you find a difference. If there is no difference then you use the length to differentiate, i.e. higher-level folder comes first.
a.Sort(Function(x, y)
Dim xFolderNames As New List(Of String)
Dim yFolderNames As New List(Of String)
'Split first path into folder names.
Do Until String.IsNullOrEmpty(x)
xFolderNames.Insert(0, Path.GetFileName(x))
x = Path.GetDirectoryName(x)
Loop
'Split second path into folder names.
Do Until String.IsNullOrEmpty(y)
yFolderNames.Insert(0, Path.GetFileName(y))
y = Path.GetDirectoryName(y)
Loop
Dim result = 0
'Compare up to as many folders as are in the shortest path.
For i = 0 To Math.Min(xFolderNames.Count, yFolderNames.Count) - 1
result = xFolderNames(i).CompareTo(yFolderNames(i))
If result <> 0 Then
'A difference has been found.
Exit For
End If
Next
If result = 0 Then
'No difference was found so put the shortest path first.
result = xFolderNames.Count.CompareTo(yFolderNames.Count)
End If
Return result
End Function)
For good measure, here's a class that encapsulates that functionality:
Imports System.Collections.ObjectModel
Imports System.IO
Public Class FileSystemPath
Implements IComparable, IComparable(Of FileSystemPath)
Public ReadOnly Property FullPath As String
Public ReadOnly Property PartialPaths As ReadOnlyCollection(Of String)
Public Sub New(fileOrFolderPath As String)
FullPath = fileOrFolderPath
Dim partialPaths As New List(Of String)
Do Until String.IsNullOrEmpty(fileOrFolderPath)
partialPaths.Insert(0, Path.GetFileName(fileOrFolderPath))
fileOrFolderPath = Path.GetDirectoryName(fileOrFolderPath)
Loop
Me.PartialPaths = New ReadOnlyCollection(Of String)(partialPaths)
End Sub
Public Function CompareTo(obj As Object) As Integer Implements IComparable.CompareTo
Return CompareTo(DirectCast(obj, FileSystemPath))
End Function
Public Function CompareTo(other As FileSystemPath) As Integer Implements IComparable(Of FileSystemPath).CompareTo
Dim result = 0
'Compare up to as many folders as are in the shortest path.
For i = 0 To Math.Min(PartialPaths.Count, other.PartialPaths.Count) - 1
result = PartialPaths(i).CompareTo(other.PartialPaths(i))
If result <> 0 Then
'A difference has been found.
Exit For
End If
Next
If result = 0 Then
'No difference was found so put the shortest path first.
result = PartialPaths.Count.CompareTo(other.PartialPaths.Count)
End If
Return result
End Function
Public Overrides Function ToString() As String
Return FullPath
End Function
End Class
It can be used with barely a change to your code:
Dim a As New List(Of FileSystemPath)
a.Add(New FileSystemPath("a\b\c"))
a.Add(New FileSystemPath("a\b\c\d"))
a.Add(New FileSystemPath("a\b\c d"))
a.Add(New FileSystemPath("a\b\c d\e"))
a.Add(New FileSystemPath("a\b\c\d\f"))
a.Sort()
Console.WriteLine(String.Join(Environment.NewLine, a))
Console.ReadLine()