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Rewrite DirectoryInfo using IShellFolder

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19 Nov 2014LGPL39 min read 172.6K   1.6K   93   52
This article describes how DirectoryInfoEx uses IShellFolder to list special / virtual directories using C#.


DirectoryInfo is a class to represent a folder in disk, it's suitable to list file system entries, but it cannot be used to represent a special folder (e.g. virtual folder that doesn't exist in the disk). You may have to use IShellFolder to enumerate these directories. DirectoryInfoEx is written to support these folders.

The project is a rewrite based on Steven Roebert's C# File Browser's code and article. His code does even more than my project, his article emphasizes on how to take advantage of the shell once you have a complete implementation (e.g. context menu, shell drag and drop, preview handler, etc.), but lacks documentation about how to create one. I rewrite part of his code (the core part) to learn how it works, and this article explains how to do the basic file operations using IShellFolder interface, in C#.

Because of my lack of knowledge, and the nature of DirectoryInfo / FileInfo, the new class is a lot simpler than CShellItem.

How to use

Basically it's the same interface of System.IO.DirectoryInfo, it support x86/x64 Desktop application only (no WinRT support)

You can construct an entry using new DirectoryInfoEx() , support parameters including

  • Path - Disk path (e.g. C:\) or Shell guid path (e.g. Desktop = ::{00021400-0000-0000-C000-000000000046})
  • CSIDL - Used to identified special directories, obsoluted because it's unchangable.
  • Environment.SpecialFolder - .Net enum of CSIDL, obsoluted.
  • KnownFolder - Known Folder Identifiers, changable by software vendors.
  • KnownFolderIds - DirectoryInfoEx enum of KnownFolderIds.

To obtain subitems, DirectoryInfoEx contains GetFileSystemInfos(), GetFileSystemInfosAsync() and EnumerateFileSystemInfos() methods for all file system entries, and Get/EnumerateDirectories/Files(Async) for directories or files only.

FileInfoEx support Open() for open and/or write a FileStreamEx, which is Stream, other helper methods include OpenText(), OpenRead() and AppendText().

For static based operations, there is DirectoryEx and FileEx static classes, and because the change in Path (e.g. Guid), please use PathEx instead.


  • Obtaining PIDL
  • IShellFolder interface
  • IStorage interface
  • IStream interface
  • My DirectoryInfoEx implementation
  • Demo

Obtaining PIDL

Folders and Files in shell namespace can be located by PIDL (ITEMIDLIST), just like folder path (or DisplayName), there are Relative PIDL and Full PIDL, just like relative path (abc.txt) and full path (c:\abc.txt).

To obtain PIDL from a string path, you can use Desktop's IShellFolder.ParseDisplayName() (see below):

ShellAPI.SFGAO pdwAttributes = 0;
DesktopShellFolder.ParseDisplayName(IntPtr.Zero, IntPtr.Zero,
     path, ref pchEaten, out pidlPtr, ref pdwAttributes);
PIDL pidl = new PIDL(pidlPtr, false); 

Obtaining PIDL from CSIDL

For special directories (e.g. virtual ones like DRIVES, or special file system directories like PROFILE), CSIDL enum has a list of them, you can use SHGetSpecialFolderLocation() to obtain its PIDL.

int RetVal = ShellAPI.SHGetSpecialFolderLocation(IntPtr.Zero, csidl, out ptrAddr);
if (ptrAddr != IntPtr.Zero)
  pidl = new PIDL(ptrAddr, false);
  return pidl;

Obtaining PIDL from KnownFolder

Because of new added directories, CSIDL, which is int based, is replaced by IKnownFolder in WindowsVista,

public interface IKnownFolder
    void GetId(...); //Return Guid of KnownFolder, see <a href="">here</a>.
    void GetCategory(...); //Return Fixed, Virtual, Common and PerUser    
    //Get IShellItem which replaced PIDL, 
    //but Current version DirectoryInfoEx (1.0.27) still uses PIDL.
    void GetShellItem(..., Guid interfaceGuid, out object shellItem); 
    //Get PIDL, so this is used instead.
    int GetIDList(...,out IntPtr itemIdentifierListPointer);
    //Get and SetPath
    void GetPath(...); 
    void SetPath(...);
    //Return a definition structure with more information of that KnownFolder.
    void GetFolderDefinition(...);

IKnownFolderManager can convert IKnownFolder from path, pidl, csidl and vice versa:

public interface IKnownFolderManager
    void FolderIdFromCsidl(int Csidl, out Guid knownFolderID);
    void FolderIdToCsidl(Guid id, out int Csidl);         
    void GetFolderIds(out IntPtr folders, out UInt32 count);
    void GetFolder(Guid id, IKnownFolder knownFolder);
    void GetFolderByName(string canonicalName, out IKnownFolder knowFolder);
    void FindFolderFromPath(string path,KnownFolderFindMode mode, out IKnownFolder knownFolder);
    void FindFolderFromIDList(IntPtr pidl, out IKnownFolder knownFolder); 

DirectoryInfoEx is pidl based, so if constructed with IKnownFolder or KnownFolderIds, it uses IKnownFolder.GetIDList() method to obtain the PIDL as id of the entry.

KnownFolderIds is a manually prepared enum with all 200 KnownFolders found on this page (up to Windows 8.1), in result, you can initialize DirectoryInfoEx using this way:

string[] txtFiles = new DirectoryInfoEx(KnownFolderIds.DocumentsLibrary)
    .EnumerateFiles("*.txt", SearchOption.TopDirectoryOnly)
    .Select(fi => fi.FullName)


Obtaining IShellFolder Interface

Desktop is the root of all shell namespace folder, you can use SHGetDesktopFolder() to obtain the IShellFolder interface for Desktop.

IntPtr ptrShellFolder = IntPtr.Zero;

if (ShellAPI.SHGetDesktopFolder(out ptrShellFolder) == ShellAPI.S_OK)
  iShellFolder = (IShellFolder)Marshal.GetTypedObjectForIUnknown(ptrShellFolder,

As for other directories (including non-file directory, e.g. MyComputer), you can use BindToObject().

if (Parent.ShellFolder.BindToObject(pidl.Ptr, IntPtr.Zero,
   ref ShellAPI.IID_IShellFolder, out ptrShellFolder) == ShellAPI.S_OK)

iShellFolder = (IShellFolder)Marshal.GetTypedObjectForIUnknown(ptrShellFolder,

IShellFolder Interface

This contains methods to manage the folder, e.g.:

  • Obtain a list of subitems (sub-folders / sub-files), e.g.
    static ShellAPI.SHCONTF folderflag = ShellAPI.SHCONTF.FOLDERS |
     /* Specify to include folders only */
    if (iShellFolder.EnumObjects(IntPtr.Zero, folderflag, out ptrEnum)
        == ShellAPI.S_OK) //return the pointer of IEnumIDList
       IEnumIDList IEnum = (IEnumIDList)Marshal.GetTypedObjectForIUnknown(ptrEnum,
       IntPtr pidlSubItem;
       int celtFetched;
       while (IEnum.Next(1, out pidlSubItem, out celtFetched) == ShellAPI.S_OK
         && celtFetched == 1)
           dirList.Add(new PIDL(pidlSubItem, false));
    /*  Add PIDL of each subdirectory to dirList, noted that in normal case you
     *  should release pidlSubItem but Steven Roebert's PIDL class is a IDisposable
     *  class which will dispose it for you.
     *  Also noted that the pidl is relative instead of full.
     *  Use GetDisplayNameOf() (see below) to get it's name. */
       if (IEnum != null) //Release resource
  • Convert PIDL back to readable path using GetDisplayNameOf():
    IntPtr ptrStr = Marshal.AllocCoTaskMem(ShellAPI.MAX_PATH * 2 + 4);
    Marshal.WriteInt32(ptrStr, 0, 0);
    StringBuilder buf = new StringBuilder(ShellAPI.MAX_PATH);
      /*  uflags is a SHGNO enum that allow you to get different folder names,
       *  e.g. "My Documents"(SHGNO.NORMAL) folder is named as
       *       "Documents"(SHGNO.FORPARSING) in file system.
       *  StrRetToBuf() convert STRRET structure to
       *  buffer usable by StringBuilder */
    if (iShellFolder.GetDisplayNameOf(pidl, uFlags, ptrStr) == ShellAPI.S_OK)
        ShellAPI.StrRetToBuf(ptrStr, pidl, buf, ShellAPI.MAX_PATH);
      if (ptrStr != IntPtr.Zero)
      ptrStr = IntPtr.Zero;
  • Retrieve IShellFolder / IStorage interface for a subfolder:

    Using SHBindToParent() :

    IntPtr pidlLast = IntPtr.Zero;
    retVal = ShellAPI.SHBindToParent(dir.PIDLRel.Ptr, ShellAPI.IID_IStorage,
      out storagePtr, ref pidlLast); 

    Or BindToStorage():

    retVal = dir.Parent.ShellFolder.BindToStorage(
                        dir.PIDLRel.Ptr, IntPtr.Zero, ref ShellAPI.IID_IStorage,
                        out storagePtr);
    /* Beside IID_IStorage interface, there is IID_IStream and
       IID_IPropertySetStorage as well. */
    if ((retVal == ShellAPI.S_OK))
      IStorage storage = (IStorage)Marshal.GetTypedObjectForIUnknown(storagePtr,
      /* Your work here, free the pointer and interface when done. */

IStorage Interface

This contains methods for creation or to manage items / subitems in the folder, e.g.

  • Rename, move or copy files, using PIDL as parameter. e.g.
    SrcStorage.MoveElementTo(SourceFileName, DestStorage,
       DestFilename, ShellAPI.STGMOVE.MOVE) != ShellAPI.S_OK) 
  • Delete files:
  • Read / Write files contents:
    /* FileStreamEx class is a customized IDisposable Stream class,
     * which uses IStream interface of a file. */
    FileStreamEx stream = new FileStreamEx(path, mode, access);
    StreamReader sr = new StreamReader(stream);

IStream Interface

This allows you to read / write data to stream objects.

  • To obtain the IStream interface, use OpenStream() (Read/Write) or CreateStream() (Create New):
    if (parentStorage.OpenStream(filename, IntPtr.Zero, grfmode, 0,
      out streamPtr) == ShellAPI.S_OK)
        stream = (IStream)Marshal.GetTypedObjectForIUnknown(streamPtr,
  • IStream contains methods like seek(), read(), write().
  • If the stream object is released, it is considered closed.

All interface objects should be released when done.

My DirectoryInfoEx Implementation

Image 1

The implementation is simpler than CShellItem, however, as FileSystemInfoEx's PIDL is exposed (via PIDLRel and PIDL property), you can implement custom operation (e.g. Extract Icon, Context Menu) externally. IShellFolder and IStorage (generate on demand) are also exposed in DirectoryInfoEx, they are automatically destroyed when disposed, do not free them yourself.

Both DirectoryInfoEx and FileInfoEx are inherited from FileSystemInfoEx, they are used as enumeration (listing) subitems, DirectoryInfoEx contains GetFiles() and GetDirectories() method for this purpose. To modify a file, use FileEx class for managing files (DirectoryEx is not implemented yet, use System.IO.Directory at this time), and FileStreamEx class for read/write files.

DirectoryInfoEx (and FileInfoEx)'s constructor accept a Path or PIDL. A number of special directories are defined in DirectoryInfoEx, including DesktopDirectory, MyComputerDirectory, CurrentUserDirectory, SharedDirectory and NetworkDirectory. For other special directories, you can obtain its PIDL by calling DirectoryInfoEx.CSIDLtoPIDL().

And a Demo

Image 2

This demo is a simple WPF application that lists the subdirectories below desktop. The Icons are obtained using SHGetFileInfo(), which takes a full PIDL parameter.

1.0.27 - This demo is removed, at this time, please check the FileExplorer instead.


  • Need to allocate time to implement IShellItem to replace ItemIDList (PIDL)



  • 08-23-09 version 0.2
    • Demo updated.
  • 11-01-09 version 0.3
    • Demo no longer load Network contents, edit the converter to disable this change.
    • DirectoryEx (static class) added.
    • PIDL class is now IDisposable and free automatically now. Also added new - internal classes ShellFolder and Storage which do the same.
    • Performance improved, no longer construct from desktop directory. (see above)
    • DirectoryInfoEx and FileInfoEx is now serializable.
  • 11-01-09 Version 0.4
    • Fixed Cache not working.
  • 11-04-09 Version 0.5
    • DirectoryInfoEx/FileInfoEx works even if the path specified is not exists (Exists == false, you have to call Create() or Refresh() before using it).
    • Refresh(), Create(), MoveTo(), Delete(), CreateSubdirectory() Open() and related instance method added.
    • Constructor support Environment path (e.g. %temp%)
    • Test project.
  • 11-07-09 Version 0.6
    • Context menu support (ContextMenuWrapper)
    • Demo updated (Context menu)
    • FileSystemWatcherEx class added.
    • Fixed FileInfoEx created by EnumFiles()(which used by GetFiles() and GetFileSystemInfos()) return incorrect Parent directory.
  • 11-08-09 Version 0.7
    • Fixed Root of all FileInfoEx equals to c:\Users\{User}\Desktop instead of a GUID.
    • Demo updated (Context menu multiselected)
  • 11-16-09 Version 0.8
    • Fixed unable Rename item in same directory.
    • Fixed ContextMenuWrapper dont return OnHover message on popup.
    • Added QueryMenuItemsEventArgs.Command, return properly for user query items.
    • Demo updated (added statusbar)
  • 12-06-09 Version 0.9
    • Fixed minor typo in DirectoryInfoEx.EmuFiles (if (iShellFolder != null))
    • Fixed DirectoryEx.Copy does not Copy directory recursively. (it currently copies an empty folder)
    • Fixed DIrectoryEx.Move (and perhaps FileEx as well) does not work correctly.
    • Fixed Wrong Operator (new) in DirectoryInfoEx.Delete(), should be override.
  • 01-04-10 Version 0.10
    • Fixed FileSystemInfoEx.getParentIShellFolder() method generate ArgumentException when pidl of items directly in Desktop directory, caused by _desktopShellFolder.BindToObject({Desktop's PIDL},...);
    • Fixed FileSystemInfoEx.Delete() return NotImplementException when get called.
    • Fixed DirectoryEx/FileEx.Exists does not check if it's directory / file.
    • Fixed FileSystemInfoEx.refresh() method does not update attribute.
    • Implemented IClonable interface in FileSystemInfoEx, DirectoryInfoEx and FileInfoEx classes.
    • Added BeforeInvoke event to ContextMenuWrapper class.
    • Added Run behavior when double click in filelist.
    • Added FileSystemWatcherEx.Filter.
  • 01-20-10 Version 0.11
    • Added: DirectoryTree in the demo; now properly refreshes when changed. (Implemented an ObservableCollection in the GetDirectoriesConverterEx class using the FileSystemWatcherEx class.)
    • Added: ContextMenuWrapper.OnQueryMenuItems.QueryContextMenu2 / QueryContextMenu3 property.
    • Added: ContextMenuWrapper.OnBeforePopup event.
    • Added: ContextMenuWrapper.OnQueryMenuItems event; now supports multilevel menu (e.g.: @"Tools\Add").
    • Added: ContextMenuWrapper.OnQueryMenuItems event; now supports GrayedItems / HiddenItems.
  • 02-15-10 Version 0.12
    • Fixed: Fullname of User/Shared directory under desktop is now its GUID instead of its file path.
    • Fixed: PIDL, PIDLRel, ShellFolder, Storage properties generated on demand to avoid x-thread issues.
    • Added: PathEx class to deal with PIDL related paths.
  • 03-14-10 Version 0.13
    • Fixed: FileSystemWaterEx ignoring remove directory event.
    • Fixed: Removed IDisposable in PIDL as it is causing an AccessViolationException, user has to free by calling the Free() method.
  • 03-16-10 Version 0.14
    • Fixed: FileSystemInfoEx now stores a copy of PIDL/Rel, will return copy of it when properties are called (to avoid AccessViolation).
    • Fixed: FileSystemInfoEx records the PIDL when constructed, as some paths are not parseable (e.g., EntireNetwork).
    • Added: Allows folder list so Non-FileAncestor directories (e.g., recycle-bin) are listed.
  • 03-18-10 Version 0.15
    • Fixed: ShellFolder/PIDL not freed in a couple locations.
    • (Please note that PIDL/ShellFolder/Store are no longer stored in the FileSystemInfoEx => must be freed by the user.)
  • 03-19-10 Version 0.16
    • Added: IShellFolder2 interface and ShellFolder2 class.
    • Added: ExtraPropertiesProvider which can list the extra file properties / list columns available (e.g., ExtraPropertiesProvider.GetProperty(file, ref ImageSummaryInformation.BitDepth);).
    • Fixed: getRelPIDL() cannot return the correct value in the File/DirInfoEx construct with string. (Attempt to return a freed up pointer.)
    • Fixed: ShellFolder not freed in two spots.
  • 04-26-2010 Version 0.17
    • Added this operator in DirectoryInfoEx.
    • Added DefaultItem and DefaultCommand in BeforePopup
    • Added WorkSpawner, which can spawn ListWork, CopyWork, MoveWork and DeleteWork to perform responsive threaded operations.
    • Fixed some XP system cannot create shared directories. (by cwharmon)
    • Removed DirectoryInfoEx file/directory list caching (_cachedFileList) as it slow down if too many files (and the old EnumDirs/EnumFiles implementation).
    • Added DirectoryInfoEx/DirectoryEx.EnumerateFiles/EnumerateDirectories/EnumerateFileSystemInfos() methods which work similar as the one in .Net4 (CancelDelegate is added to make it cancelable.)
    • Added FileEx.ReadLines/ReadAllLines() methods.
    • Added IOTools.CopyFile() method which support cancel.
    • Added FileSystemInfoEx.FromString() method.
  • 05-25-2010 Version 0.18
    • WPF File Explorer User Control (DirectoryTree and FileList) now available.
    • Fixed DirectoryInfoEx.EnumerateDirectories return files when listing network directories.
    • Added ExComparer class, which enable sorting an array of FileSystemInfoEx entries.
    • Fixed DriveInfoEx return incorrect TotalSize. DriveInfoEx constructor now accept full drive name ("C" and "C:\" both accepted now)
    • (REMOVED) Added a check for NonEnumerated items so DirectoryInfoEx.EnumerateDirectories wont return some system directories (e.g. C:\MSOCache)
    • Added IOTools.GetRelativePath. Documented IOTools's static methods.
    • Added IOTools.ShellFolderToCSIDL() and CSIDLToShellFolder() static methods.
    • Added constructor of DirectoryInfoEx which support Environment.ShellFolder.
    • Fixed DirectoryInfoEx.EnumerateFiles ignore SearchPattern.
    • Fixed Context menu disappear in some case. (By cwharmon)
    • Updated DirectoryInfoEx/FileInfoEx listing code to improve speed.
    • Added Progress Dialog for all Work, WorkBase.IsProgressDialogEnabled and ProgressDialog.
  • 07-17-2010 Version 0.19
    • Added FileTypeInfoProvider
    • Fixed ArgumentException when getting storage of C:\{User}\Desktop.
  • 08-22-2010 Version 0.20
    • Fixed ShellProgressDialog still running after closed.
    • Added LinkSummaryInformation in ExtraPropertiesProvider.
  • 11-04-2010 Version 0.21
    • Small update to CustomMenuStructure class.
    • Fixed FileSystemInfoEx.getRelativePIDL() and getParentPIDL() that return relPIDL that is not a clone, which will crash if attempted to Free. (e.g. in DirectoryEx.Exists())
  • 03-01-2011 Version 0.22
    • Added ImageExtractor, which uses IExtractImage to generate thumbnails.
    • Added PreviewHelper and PreviewControl, which is a IPreviewHandler.
    • Fix illegal PIDL for Directory under directory
  • 12-16-2013 Version 0.24
    • Change access to FileSystemInfoEx.PIDL/PidlRel to extension methods (RequestPIDL/RelPIDL)
    • Fixed a memory leak when listing.
  • 12-24-2013 Version 0.25
    • Fixed OpenWithInfo.GetExecutablePath()
  • 11-10-2014 Version 1.0.26
    • Fixed two crashes related to x64 mode.
    • Added DirectoryInfoEx.ShellFolderType (Environment.SpecialFolder).
  • 11-19-2014 Version 1.0.27
    • Added DirectoryInfoEx.GetFileSystemInfosAsync(), GetDirectoriesAsync() and GetFilesAsync() async methods.
    • Added KnownFolder support (See MSDN)


This article, along with any associated source code and files, is licensed under The GNU Lesser General Public License (LGPLv3)

Written By
Hong Kong Hong Kong

Comments and Discussions

QuestionHow to get a PIDL from a path like "c:\temp\image.jpg"? Pin
Jakob Farian Krarup11-Nov-22 8:58
Jakob Farian Krarup11-Nov-22 8:58 
QuestionThrowExceptionForHR Pin
Member 930529318-Sep-12 3:02
Member 930529318-Sep-12 3:02 
GeneralCrashes on win7 Pin
Xmen Real 18-Jul-12 19:08
professional Xmen Real 18-Jul-12 19:08 
GeneralRe: Crashes on win7 Pin
Leung Yat Chun19-Jul-12 20:24
Leung Yat Chun19-Jul-12 20:24 
GeneralRe: Crashes on win7 Pin
Xmen Real 20-Jul-12 0:03
professional Xmen Real 20-Jul-12 0:03 
GeneralRe: Crashes on win7 Pin
Xmen Real 20-Jul-12 14:44
professional Xmen Real 20-Jul-12 14:44 
GeneralRe: Crashes on win7 Pin
Leung Yat Chun22-Jul-12 20:55
Leung Yat Chun22-Jul-12 20:55 
GeneralRe: Crashes on win7 Pin
Xmen Real 6-Jan-16 17:37
professional Xmen Real 6-Jan-16 17:37 
GeneralVersion 18 : ArgumentException Fix Pin
Leung Yat Chun9-Jun-10 8:45
Leung Yat Chun9-Jun-10 8:45 
GeneralVersion 17 Notes Pin
cwharmon29-Apr-10 3:25
cwharmon29-Apr-10 3:25 
GeneralRe: Version 17 Notes Pin
Leung Yat Chun29-Apr-10 5:30
Leung Yat Chun29-Apr-10 5:30 
GeneralRe: Version 17 Notes Pin
cwharmon29-Apr-10 7:34
cwharmon29-Apr-10 7:34 
GeneralRe: Version 17 Notes Pin
Leung Yat Chun29-Apr-10 8:45
Leung Yat Chun29-Apr-10 8:45 
GeneralRe: Version 17 Notes Pin
cwharmon29-Apr-10 9:08
cwharmon29-Apr-10 9:08 
GeneralRe: Version 17 Notes - Performance Issue Pin
cwharmon21-May-10 11:23
cwharmon21-May-10 11:23 
GeneralRe: Version 17 Notes - Performance Issue Pin
Leung Yat Chun21-May-10 19:21
Leung Yat Chun21-May-10 19:21 
GeneralRe: Version 17 Notes - Performance Issue Pin
cwharmon25-May-10 4:18
cwharmon25-May-10 4:18 
NewsVersion 0.17 update log Pin
Leung Yat Chun26-Apr-10 7:03
Leung Yat Chun26-Apr-10 7:03 
GeneralRe: Version 0.18 update log Pin
Leung Yat Chun24-May-10 8:08
Leung Yat Chun24-May-10 8:08 
GeneralContext Menu: Default Action Pin
cwharmon26-Mar-10 4:23
cwharmon26-Mar-10 4:23 
GeneralRe: Context Menu: Default Action Pin
Leung Yat Chun26-Mar-10 5:45
Leung Yat Chun26-Mar-10 5:45 
GeneralRe: Context Menu: Default Action Pin
cwharmon29-Mar-10 4:52
cwharmon29-Mar-10 4:52 
GeneralRe: Context Menu: Default Action [modified] Pin
Leung Yat Chun29-Mar-10 5:36
Leung Yat Chun29-Mar-10 5:36 
GeneralRe: Context Menu: Disappears Pin
cwharmon18-May-10 13:01
cwharmon18-May-10 13:01 
GeneralRe: Context Menu: Disappears Pin
Leung Yat Chun19-May-10 3:16
Leung Yat Chun19-May-10 3:16 

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