Sorting Directory GetFiles

Question

System IO Directory GetFiles   returns a string     What is the default sort order for the returned values   I m assuming by name  but if so how much does the current culture effect it   Can you change it to something like creation date    Update  MSDN points out that the sort order is not guaranteed for  Net 3 5  but the 2 0 version of the page doesn t say anything at all and neither page will help you sort by things like creation or modification time   That information is lost once you have the array  it contains only strings    I could build a comparer that would check for each file it gets  but that means accessing the file system repeatedly when presumably the  GetFiles   method already does this   Seems very inefficient

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The MSDN Documentation states that there is no guarantee of any order on the return values  You have to use the Sort   method

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In  NET 2 0  you ll need to use Array Sort to sort the FileSystemInfos   Additionally  you can use a Comparer delegate to avoid having to declare a class just for the comparison   DirectoryInfo dir   new DirectoryInfo path   FileSystemInfo   files   dir GetFileSystemInfos        sort them by creation time Array Sort lt FileSystemInfo gt  files  delegate FileSystemInfo a  FileSystemInfo b                                                                                return a LastWriteTime CompareTo b LastWriteTime

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You could write a custom IComparer interface to sort by creation date  and then pass it to Array Sort   You probably also want to look at StrCmpLogical  which is what is used to do the sorting Explorer uses  sorting numbers correctly with text

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Just an idea  I like to find an easy way out and try re use already available resources  if I were to sort files I would ve just create a process and make syscal to  DIR  x  Folders SubFolders      s  b  on  and capture the output    With system s DIR command you can sort by     O          List by files in sorted order  sortorder    N  By name  alphabetic        S  By size  smallest first               E  By extension  alphabetic   D  By date time  oldest first               G  Group directories first    -  Prefix to reverse order  The  S switch includes sub folders   I AM NOT SURE IF D   By Date Time is using LastModifiedDate or FileCreateDate  But if the needed sort order is already built-in in the DIR command  I will get that by calling syscall  And it s FAST  I am just the lazy guy     After a little googling I found switch to sort by particular date time -   t     TimeField    Specifies which time field to display or use for sorting  The following list describes each of the values you can use for TimeField    Value Description  c   Creation a   Last access w   Last written

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A more succinct VB Net version  if anyone is interested  Dim filePaths As Linq IOrderedEnumerable Of IO FileInfo        New DirectoryInfo  c  temp   GetFiles         OrderBy Function f As FileInfo  f CreationTime  For Each fi As IO FileInfo In filePaths     Do whatever you wish here Next

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A more succinct VB Net version   is very nice  Thank you   To traverse the list in reverse order  add the reverse method     For Each fi As IO FileInfo In filePaths reverse     Do whatever you wish here Next

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You are correct  the default is my name asc  The only way I have found to change the sort order it to create a datatable from the FileInfo collection   You can then used the DefaultView from the datatable and sort the directory with the  Sort method   This is quite involve and fairly slow but I m hoping someone will post a better solution

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You can implement custom iComparer to do sorting  Read the file info for files and compare as you like    IComparer comparer   new YourCustomComparer    Array Sort System IO Directory GetFiles    comparer     msdn info IComparer interface

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If you want to sort by something like creation date you probably need to use DirectoryInfo GetFiles and then sort the resulting array using a suitable Predicate

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Here s the VB Net solution that I ve used   First make a class to compare dates   Private Class DateComparer     Implements System Collections IComparer      Public Function Compare ByVal info1 As Object  ByVal info2 As Object  As Integer Implements System Collections IComparer Compare         Dim FileInfo1 As System IO FileInfo   DirectCast info1  System IO FileInfo          Dim FileInfo2 As System IO FileInfo   DirectCast info2  System IO FileInfo           Dim Date1 As DateTime   FileInfo1 CreationTime         Dim Date2 As DateTime   FileInfo2 CreationTime          If Date1  gt  Date2 Then Return 1         If Date1  lt  Date2 Then Return -1         Return 0     End Function End Class   Then use the comparer while sorting the array   Dim DirectoryInfo As New System IO DirectoryInfo  C     Dim Files   As System IO FileInfo   DirectoryInfo GetFiles   Dim comparer As IComparer   New DateComparer   Array Sort Files  comparer

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From msdn      The order of the returned file names is not guaranteed  use the Sort   method if a specific sort order is required    The Sort   method is the standard Array Sort    which takes in IComparables  among other overloads   so if you sort by creation date  it will handle localization based on the machine settings

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If you re interested in properties of the files such as CreationTime  then it would make more sense to use System IO DirectoryInfo GetFileSystemInfos     You can then sort these using one of the extension methods in System Linq  e g    DirectoryInfo di   new DirectoryInfo  C       FileSystemInfo   files   di GetFileSystemInfos    var orderedFiles   files OrderBy f   gt  f CreationTime     Edit - sorry  I didn t notice the  NET2 0 tag so ignore the LINQ sorting  The suggestion to use System IO DirectoryInfo GetFileSystemInfos   still holds though

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Dim Files   As String Files   System IO Directory GetFiles  C     Array Sort Files

[.net] Sorting Directory.GetFiles()

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