ExpTreeLib is a Class Library which provides much of the functionality of Windows Explorer. It is typically used to implement File/Directory utilities and
Document Management applications.
The library's central class is
CShItem which is an API based superset of the .NET
It also contains a User Control,
ExpTree, which is an Explorer-like TreeView of the
folders of the Windows Shell.
ExpTree supports system context menus, drag from and drop on, and normal Shell-like navigation. The
library provides dynamic notification of all changes
to the contents of the Shell namespace (the
FileSystem plus), classes to support
drag & drop to/from various
controls, and several utility functions that are useful in their own right. Included in the download package are
example forms that illustrate the
use of the library to build a full Windows Explorer-like application. The demo forms may be easily modified and/or extracted from to meet the needs of your application. Also
included is a demo form that uses the library without an
ListView and works with files displayed in a
This article only gives a summary of ExpTreeLib and the demo project. To keep the article to a reasonable length and to provide a better reference source, I
provide a Help File (ExpTreeLib.chm) as a separate download. In addition to the usual Help content, the Help File contains guidance on how to use the
and demo forms in your own applications and details on how the library and demo
forms work. The first step in using the library should be
downloading and browsing through the Help File! For a better understanding of the
library, you may also browse
through the original CodeProject article.
You may also download the demo package to see the library in action without actually downloading the
source or Help.
Simply displaying the structure and content of folders is not enough for a useful application. The real question is what the
application can do with the displayed items. Out of the box, the main demo forms (
(a C# version of
provide the key functionality of Windows Explorer, but in a form that is easily modified to suit the needs of
ExpTree and the main demo forms support the following
- Automatic update of the TreeView or ListView when any change is made by any process to the
displayed folders or their content.
- Dropping a file/folder onto ExpTree and/or the ListView. This feature supports normal Windows Control-Key modifiers
and right button drag menu to instruct the receiving control to copy or
move the file(s)/folders(s) to the target
folder. The drag source may be itself or any application (including Windows Explorer)
that provides at least
DataFormatted information. One useful
class of such applications is Windows email clients (Outlook, Outlook Express,
Thunderbird, Windows Live Mail, etc.)
- Dragging file(s)/folder(s) from the ExpTree or the ListView. Normal Windows
Control-key and right button drag operations are supported. The drop
be itself or any window (including Windows Explorer) that accepts at least
- Right-click on a file/folder to display the same ContextMenu that Windows
Explorer would display on right-click. File/folder rename
- Edit of the first column of the ListView to rename a file/folder -- if and only if the first
the file/folder name.
- Column-click sorting (with Sort Glyph) of the ListView columns when displayed in
- Selected item(s) delete in response to the Delete key or Context Menu.
- Double-click on a file to "Open" it.
- Substantial optimization of both the library and demo forms relative to earlier
Downloadable Zip packages for ExpTreeLib
- Source code -- The full source as a Visual Studio 2008 Solution with four
Projects including a C# complete project implementing
C#. The VS2008 Solution should upgrade without errors to a VS2010 Solution. This
ExpTreeLib - the library.
ExpTree_Demo -- Three demo/example forms demonstrating how to use
- Documentation - The documentation set for the library and examples organized as
a website. This material is also included in the Help File download as part of
the .chm file.
frmThread implemented in C# to illustrate how a C# developer can
ExpTreeLib, including the
Set as Startup Project to run this project.
- Demo -- Just the executable and its' required .dll file for a quick look.
- Help File -- A .chm file including substantial additional documentation of the
demo/example forms and how to use them to build your own applications.
Version 1.0 of this library was initially
published on CodeProject in 2004. It provided a static view of the Shell
namespace in a TreeView. Through multiple revisions it
advanced to a still static but refreshable view and came to also support a (mostly correct) form of
drag & drop, finally
arriving at Version 2.11 as the
original CodeProject article now describes and provides as downloads. The last update to that version was
posted as Version 2.12 in 2012. The drag & drop facility available in that version is also published in a now
That article may be of interest to those who prefer to use Version 2.12 instead of Version 3.0 which is covered here.
In order to correctly implement Drag & Drop, it was necessary to substantially rewrite the
to add several supporting classes. The rewrite of
CShItem included a
mechanism that provides notification of any changes to the folders of interest to the application. This allows
any other controls to be notified of changes and to update the GUI. This change
transformed ExpTreeLib from a static view of the Shell namespace to a
Dynamic view. I made other enhancements, most notably System Context
Menus, to the library,
ExpTree, and to a demo form.
This work's result was Version 2.14, also known in the forum as the "Unpublished Version".
Version 2.14 has been distributed to a number of people who contacted me
through the forum of the original article. Both 2.11 and version 2.14 have proven
popular and are still discussed in the forums of the original article and in
direct email to me.
The most recent update to Version 2.14 was sent to the distribution list on
A few 3rd party Shell Extensions caused errors in the library. Version 3.02 has enhanced error handling to deal with those errors. Specifically, when a Shell Extension requires a 3rd party .dll and that .dll fails to load, previous versions would not handle that error correctly. This has been fixed.
Corrected a memory leak. Also corrects problems that seemed to be introduced by Visual Studio 2012.
Thanks to Jens Madsen,
SystemImageListManager now will deal with XL Icons with overlays.
Version 3.01 is primarily a bug fix release. It also includes an additional Project with an instrumented version of frmThread.vb and two other Forms that may be of mild interest to a developer who wishes to dig into ExpTreeLib. Release Notes for 3.01 are in the Documentation Project included in the Source download.
Version 3.00 of this package adds optimization of both the ExpTreeLib library
and the demo forms. Much of this optimization is not needed when
the user's application is running on a Windows XP system. However, it is very
important when the application is running on later (Vista/Win7) systems and
accessing large server based folders. Version 3.00 also adds a Help File (.chm),
new and corrected comments, and a collection of additional documentation in
the form of HTML pages, including additional information about how to modify
or extract from the demo forms for use in your own projects. The
documentation of the demo project is also included in the Help File available as a
Summary of changes relative to Version 2.12
More detail is available in the Version 2.14 and Version 3.00 Release Notes found in the Help File. To summarize, Version 3.00 improves
on Version 2.12 by providing:
- Dynamic Change Notification of all changes to the Shell namespace that are of
interest to the application that are made by all
processes on the system.
- A much more robust handling of Drops onto
ExpTree and properly coded ListViews
or other Controls. See the demo forms and the documentation for how to properly
code ListViews and other Controls.
- Drags from ExpTree and properly coded ListViews.
- Windows System Context Menus in ExpTree and properly coded ListViews. See demo
forms for how to properly code ListView System Context Menus.
- All changes needed to compensate for differences between various versions of Windows
- Win7, Vista, XP.
- Significant improvements in GUI responsiveness for applications running on Windows7
and Vista systems and accessing Remote Folders. XP was always fast enough.
- New demo forms which incorporate changes to improve
responsiveness and to be easier to modify and/or extract from for use in applications.
- A C# version of the most complex demo form to illustrate how to use
- Very significant improvements to the Documentation of both
and the demo forms. This includes provision of a Help File and corresponding improvements
in the XML comments within the code.
- Use of Win7/Vista Themes for
Using ExpTreeLib and the demo forms
There are a number of approaches to take to integrate
ExpTreeLib into your own application.
- Start from scratch using the documentation and worked examples to use some or all of
functionality. Note that it is not necessary to use any Windows Forms components. A Console app might
- or Start with a copy of one of the demo project's forms, adding your application's
Controls and code. See the topic "Building an App" in the Help File.
- or Copy the
ExpTree and/or the ListView Controls and code from one of the demo forms to your own
form(s). See the topic "Deriving from a Demo Form" in the Help File.
Building a Form to use ExpTreeLib
The first article gives an overview on how to use the
ExpTree Control in your application. Also see the topic
"Deriving from a Demo Form" in the Help File.
To summarize using
frmThread as a model:
- Add a reference to the
ExpTreeLib DLL to your project.
- Add the
ExpTree control to the Visual Studio Toolbox.
- Add an ExpTree control to your form.
- Add the appropriate
using in C#) statements to your form. See the
demo forms for usage.
- Add an Event Handler to handle the ExpTree1.ExpTreeNodeSelected Event to receive
notification of Node Selections:
Private Sub AfterNodeSelect(ByVal pathName As String, ByVal CSI As CShItem) _
- If using
SystemImageListManager to provide file and folder icons
for a ListView, add the code found in either
demo form in the
#Region "Form Load/VisibleChanged lv1 HandleCreated" region.
- If using a ListView to display Files/Folders in a manner similar to the demo forms, and if you wish to support
drag & drop from/to that ListView, add the appropriate Declarations as found in either of the demo forms to
declare and initialize instances of
You must also set the
ListView.Tag to be the
CShItem passed in as CSI in the
AfterNodeSelect handler whose declaration is shown above. This is needed to
properly handle drops onto a ListView that currently has no Items.
- To support Dynamic Updating of your ListView:
- Add the code found in the
Dynamic Update Handler Region of either demo form to your code.
- Add an
AddHandler statement to your
AddHandler CShItemUpdate, AddressOf UpdateInvoke
- Declare a FormClosing Event Handler to Remove that Handler:
Private Sub frmThread_FormClosing(ByVal sender As Object, _
ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
RemoveHandler CShItemUpdate, AddressOf UpdateInvoke
- For completeness sake, also remove the handler in the
Dispose routine of your
- See the demo forms, the Help file, and the other included documentation for additional code elements
needed to support your application's use of
The demo forms
There are several demo forms in the ExpTree_Demo Project. To see a particular form in action, modify the Module modMain in that
project by uncommenting the
Application.Run(someform) statement and ensuring that all others are commented out.
frmThreadCS, set its' project to be the Startup Project in Visual Studio.
These forms will do normal file manipulation as is posible in Windows Explorer.
However, they primarily exist to provide worked examples
of how to use
CShItem, and the related classes.
This form is a fully working start point for any form which requires an ExpTree and ListView with enough room left for
application specific controls.
frmTemplate includes all optimizations that do not
require use of a
BackgroundWorker. Because of that omission, it is much simpler
to understand and to work with. For applications that will be working with small
to medium Local Folders,
frmTemplate will give fully acceptable performance. It
is not recommended for applications that will be working with Remote Folders.
- Use of the
ExpTreeNodeSelected Event Handler.
- Use of
ClvDropWrapper to support Drags From and Drops onto the
- Handling of dynamic update Events from CShItemUpdate Events.
- Full Context Menus in the ListView.
- Use of
LVColSorter for Sorting on
- Use of
MakeLviItem as a custom
ListViewItem builder which builds
ListViewItems which include the properties useful for
- Use of
ListViewSortGlyph.SetSortIcon to set the Sort Glyph on the Sort Column.
SortLVItems for how to perform a Refresh of the
ListView in response to a Refresh command from the Context Menu.
ListViewItem editing (first
- Proper handling of the Delete Key.
- Shows how to handle a
DoubleClick on a
frmThread is a fully working start point for any form which requires an ExpTree and ListView and is likely to access large and/or
remote Folders, requiring a multi-threaded approach to improve GUI responsiveness. As with
frmTemplate, it has
enough room left for application specific controls.
- All features included in
- Use of a
BackgroundWorker Thread to populate a
ListView with information
that may take excessive time to gather.
frmThread - C# version
Included in the Source download is a separate C# Project whose only form is
frmThread implemented in C#. Aside from the implementation language, it is identical to the
VB.Net version. In the full Solution, set the Project "CS" to be the Startup
Project to run this form.
This form illustrates how to use
ControlDropWrapper to handle Drag To/Drop On events for a DataBound
It is a relatively bare bones form and should only be used to aid understanding of use of
The definitive explanation of how
ExpTreeLib and the demo forms work is the Source code. A full explanation of the details would take
at least as many lines of text as there are lines of code - probably much more.
The definitive reference to the classes is the Help file.
The Help file documents all important public classes and their methods, events, and properties.
Appropriate comments are also displayed
by Visual Studio's Intellisense mechanism. The Help file also includes substantial supplemental documentation.
The supplemental documentation is also available as a Project in the Source
download. That Project - named "Documentation" contains all the supplemental
documentation in the form of a "web site" like collection of HTML
pages which can be
viewed in your favorite Browser. Simply open the file
Documentation\Exp_Index.htm and follow the links. The first article in this
series contains valuable information, especially when supplemented by the
Release Notes for Version 2.14 and Version 3.00 which are found in the Help file
and the Documentation Project. You may also ask a question in the Forum for this
How it Works - Key Concepts
Rather than make this article too long, here is a summary of some key points. The concepts to take away are in Bold.
The Help file has much more detail.
The CShItem Class
CShItem class is the primary class of ExpTreeLib. Each instance of
wraps a collection of information about a
ShellNamespace Item. Shell Namespace
Items include both FileSystem Items and non-FileSystem Items. Windows
Explorer (WinExp) is the visible representation of the Shell namespace. An
CShItem is the equivalent of one of the Items (file or folder) as
displayed by WinExp.
CShItem uses the Windows API to obtain and to obtain
information about those Items. Every major method or property of ExpTreeLib
involves or requires a
CShItem. In the demo forms, every
ListViewItem has a
CShItem in its
.Tag property. In
every Row in the
DataGridView is DataBound to a
CShItem class maintains a shared tree structure that contains
CShItem instances that are Items of Interest to the application. Given an
CShItem called "
CSI" that represents a folder in the Shell namespace,
the application can obtain
CShItems representing the contents of that
CSI.Files properties or by calling the
methods. Once the application
has obtained a
CShItem via one of these properties or methods, it is considered
an Item of Interest to the application until it is explicitly released
CSI.ClearItems method. To conserve memory, an Application should
always explictly release unneeded file CShItems. See the Version 2.14
Release Notes for details.
Each Item of Interest is represented by exactly one
is stored in the internal tree in exactly the same position that the
corresponding Shell NameSpace Item is located in the Shell namespace. When a
change is made to the Shell namespace,
CShItem is notified by a Windows Message
of that change. If the change affects one or more Item of Interest in
the internal Tree, an Event is Raised to notify the application of that change.
The application can then make corresponding changes to the GUI and do whatever
else the application needs to do to reflect that change. See the demo
forms for examples of how the application may handle Notification Events.
There is no Publicly Accessible CShItem Constructor (Sub New).
are obtained using the .Directories or .Files Properties. In rare cases the
application may need to obtain a
CShItem corresponding to a file system path. In
those cases, use the
CShItem.GetCShItem(Path) method or one of its
This is normally only done to change the
RootItem property of
ExpTree so as to
root the TreeView in a folder that is specific to the Application.
Drag and Drop
Drags from and Drops onto
ExpTree or any properly configured ListView behaves
dragging from or dropping onto Windows Explorer items.
A properly configured
ListView will contain
ListViewItems which all have a
CShItem in their .Tag Properties. Drops onto any other type of
Control (eg a
DataGridView) is possible if the Control is associated with a single folder. In the case of other application specific Controls, Drops are accomplished by associating the
Control with a New instance of a
class. Drags from an application specific
ListView or TreeView are accomplished by associating the
a new instance of the
Just like Windows Explorer, successful Drag and Drop operations will result in
the Dragged Files and/or Folders being Copied or Moved to another folder.
Right Button Drops will display the same menu of choices as displayed by Windows
Explorer for the same operation. Since any successful Drop will result in a
change to the underlying Shell namespace,
CShItem will be notified of the change
and will Raise one or more
CShItemUpdate events thus notifying the application
of the change.
Solving Responsiveness Issues
Writing a CodeProject article about Version 2.14 of ExpTreeLib had been on my To
Do list for years. However, I had never gotten around to it. Recently, users of
both 2.11 and 2.14 reported performance/responsiveness issues. The common thread
was that everything was fine until they started using Windows 7 clients to
access large Folders on a Server. The same applications had no problems
accessing those same Folders when running XP on the client. I investigated. The
investigation and the results of that investigation are covered in depth in the
supplemental Documentation and are summarized below. The results led to a number
of large and small optimizations of both ExpTreeLib and the demo forms. Note
- the tested operations against copies of the Test Folders on the Local machine take between
15 and 1200
milliseconds using either unoptimized or optimized code. Operations on normally
sized Local Folders are effectively instantaneous. Optimization produces
noticeable improvements only when operating against Remote Folders.
My test environment consisted of a Win7 client accessing two different folders on a
slow, small, WHS system running Server 2003. One folder contained 3,000 files of
various types. The other folder contained 2,000 empty sub-Folders.
Optimization came in three phases, each with its own culprits and solutions:
- Optimization of code in the demo form itself. This major changes were:
These changes made an improvement, but, were not enough to create an acceptable user experience
on the Test Folders.
- Elimination of use of
GetAttr function. This included changing the definition of a
CShItem property, and adding a new one.
- Simply using
AddRange instead of multiple
Adds to fill the
CShItem properties (Length and the Creation, LastWrite, LastAccess
dates) are obtained using
DirectoryInfo classes. I have long been aware
that these classes are not optimal, especially when accessing Remote
Files/Folders. I added a class to define the Windows API
FindNextFile (FFF/FNF) methods. Unfortunately, the benefits of
using FFF/FNF only occur when all Items are retrieved in one pass using the
SafeFindHandle returned by the initial call to
is a large improvement over
DirectoryInfo, using it from the GUI Thread
still caused serious delays in GUI responsiveness on the Test Folders. The design and usage of
CShItem makes it complex to incorporate the use of FFF/FNF in a separate Thread
CShItem. I instead created
frmThread to use FFF/FNF from a
gather the required information for the contents of large Folders.
The Windows handling of the
HasSubFolders attribute changed sometime after XP
The earlier version would always return True for a remote folder. The current
definition queries the remote folder to obtain a accurate value. Acquiring
HasSubFolders went from an operation which would take no detectable time to one
that was very costly.
CShItem would routinely get the value of that attribute
for every folder
CShItem created. This one change to the API accounts for the
majority of the performance differences between
ExpTreeLib on XP versus
ExpTreeLib on later systems.
CShItem to only retrieve
HasSubFolders when the application explicitly asked for it and also changed
CShItem to revert to the XP usage of always returning True for Remote Folders.
ExpTree does explicitly use
HasSubFolders to determine if a
should be Expandable. The effect of the optimization is that
representing Remote Folders will always be Expandable, even if the folder is
empty. This is corrected on an attempt to Expand the
Made changes to the
ExpTree Control to eliminate redundant and time consuming
code. Eliminated the use of the .NET method
behaves very inefficiently when adding a node to the
The results of the Optimizations are given below. F1 is a remote folder
containing 3,000 files of various types. F2 is a remote folder containing 2,000
sub-Folders. All times are in seconds:
Original GUI Freeze*||
Optimized GUI Freeze*||
Optimized Total Time**|
Display Contents of F1 in ListView||
Direct Access to sub-folder of F2||
Expand folder F2 node in Exptree||
* Time before the GUI becomes responsive to user action.
** Time to fully complete the information gathering.
Your mileage may vary! I am interested in hearing about any significant differences and the circumstances that may have contributed
to those differences. Compare to the time it takes to do the same operation via Windows Explorer. Note:
referencing a remote folder on a unavailable machine will always encounter network timeout delays.
- Calum McLellan made significant contributions that improved this control. Calum's
Explorer ComboBox and ListView in VB.NET
extends this library with both
ListView classes. The ContextMenu portion of my library and Demos are
derived from Calum's work. Calum uses an early version of
in his project. It lacks all optimization and some Vista/Win7 modifications.
- My original version of
ExpTreeLib contained a class for accessing System image lists. Some important
fragments of that class survive in
SystemImageListManager. My original
was simply a translation from C# to VB.NET of some of Steve McMahon's System image
list class which may be found here. Steve's class has substantial additional capabilities
for drawing icons and attaching them to other types of controls.
- Steven Roebert's article describes a C# package
that was, in part, inspired by my original article. His work formed the basis of my fixes to the original Drag & Drop and
change notification. His code has not been updated or supported since 2006 and seems, from the Forum, to have significant
problems with Vista/Win7 and 64-bit OSes.
- Eric Woodruff's Sandcastle HelpFileBuilder is a terrific tool for building Help
- I have also been helped by contributors to the Forums of my previous articles
and by other open source code and discussions found in CodeProject and elsewhere
on the Internet.
- 01/09/2014 -- Version 3.02 Fix for non-compliant 3rd party Shell Extensions, memory leak, and minor enhancements including XL Icons with overlays.
- 11/14/2012 -- Version 3.01 Bug fixes, and minor enhancements.
- 07/16/2012 -- Version 3.00. Initial submission to CodeProject of this, the third, article.
- 04/20/2012 -- Version 2.12. Update of Downloads and first article - includes all optimization fixes that can be implemented in version 2.11.
Also includes the rollup of all 2.11 bug fixes.
- 12/26/2010 -- Last update to 2.14 sent to mailing list.
- 12/12/2006 -- (approximate date) Version 2.14, (the "unpublished version") sent to those who requested it.
- 03/12/2006 -- Version 2.11. Updated to both articles to support VS2005.
- 09/16/2005 -- Version 2.1. Update to source and demo to make equal to same files in second article.
- 09/16/2005 -- Publication of second
article in this series.
- 08/23/2005 -- Version 2 release - Update to part
1 of this article series, source, and demo. Adds a form of Drag & Drop.
- 10/11/2004 -- Initial version of first article and ExpTreeLib - Version 1.0