Q267908: HOWTO: Enumerate the Subkeys of an Open Registry Key
Article: Q267908
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:5.0,6.0
Operating System(s):
Keyword(s): kbAPI kbRegistry kbSDKWin32 kbVBp kbVBp500 kbVBp600 kbGrpDSVB kbDSupport kbCodeSnippet
Last Modified: 11-JAN-2001
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The information in this article applies to:
- Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0
- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0
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SUMMARY
=======
This article provides an example of how to use API functions to programmatically
find keys in the system registry. The sample demonstrates searches of root
subkeys for specified text strings. An option to perform case-sensitive text
searches is presented.
The example uses the RegEnumKeyEx API function to enumerate subkeys of a
specified open registry key. The function retrieves information about one subkey
each time it is called.
MORE INFORMATION
================
The following steps create a project that displays the subkeys of an open
registry key in a list box. You can use search criteria to isolate specific keys
to be returned.
Step-by-Step Example
--------------------
1. Start a new project Standard EXE in Visual Basic. Form1 is created by
default.
2. Set the BorderStyle property of Form1 to 4 - FixedToolWindow.
3. Add the following controls to Form1: three Labels, two ComboBoxs, one
TextBox, two CommandButtons, one CheckBox, and one ListBox.
4. Set the Style property for each ComboBox to 2 - Dropdown List.
5. Add the following code to the General Declarations section of Form1:
Option Explicit
Private Type FILETIME
intLow As Long
intHigh As Long
End Type
Private Declare Function RegOpenKeyEx Lib "advapi32.dll" _
Alias "RegOpenKeyExA" _
(ByVal hKey As Long, _
ByVal lpSubKey As String, _
ByVal ulOptions As Long, _
ByVal samDesired As Long, phkResult As Long) As Long
Private Declare Function RegEnumKeyEx Lib "advapi32.dll" _
Alias "RegEnumKeyExA" _
(ByVal hKey As Long, _
ByVal dwIndex As Long, _
ByVal lpName As String, _
lpcbName As Long, _
ByVal lpReserved As Long, _
ByVal lpClass As String, _
lpcbClass As Long, _
lpftLastWriteTime As FILETIME) As Long
Private Declare Function RegCloseKey Lib "advapi32.dll" _
(ByVal hKey As Long) As Long
Const HKEY_CLASSES_ROOT = &H80000000
Const HKEY_CURRENT_USER = &H80000001
Const HKEY_LOCAL_MACHINE = &H80000002
Const HKEY_USERS = &H80000003
Const ERROR_SUCCESS = 0&
Const SYNCHRONIZE = &H100000
Const STANDARD_RIGHTS_READ = &H20000
Const KEY_QUERY_VALUE = &H1
Const KEY_ENUMERATE_SUB_KEYS = &H8
Const KEY_NOTIFY = &H10
Const KEY_READ = ((STANDARD_RIGHTS_READ Or _
KEY_QUERY_VALUE Or _
KEY_ENUMERATE_SUB_KEYS Or _
KEY_NOTIFY) And _
(Not SYNCHRONIZE))
Dim strBranch As Long
Private Sub Combo1_Click()
' Set the branch to search depending on
' what is selected in the ComboBox
Select Case Combo1.ListIndex
Case 0
strBranch = HKEY_CLASSES_ROOT
Case 1
strBranch = HKEY_CURRENT_USER
Case 2
strBranch = HKEY_LOCAL_MACHINE
Case Else
strBranch = HKEY_USERS
End Select
End Sub
Private Sub Command1_Click()
Dim i As Integer
Dim lngKeyHandle As Long
Dim lngResult As Long
Dim lngCurIdx As Long
Dim strValue As String
Dim lngValueLen As Long
Dim strClass As String
Dim lngClassLen As Long
Dim strResult As String
Dim lngTime As FILETIME
Dim strSearch As String
Dim intSearchLen As Integer
Dim blnMatch As Boolean
i = 0
' Clear the current results
List1.Clear
' Assign the new string to search for
strSearch = Text1.Text
intSearchLen = Len(strSearch)
' Open the Root Branch to search
lngResult = RegOpenKeyEx(strBranch, _
"", _
0&, _
KEY_READ, _
lngKeyHandle)
If lngResult <> ERROR_SUCCESS Then
MsgBox "Cannot open key.", , "Search Registry Keys"
Else
' If the Root branch can be opened, disable
' the buttons and begin the search
Command1.Enabled = False
Command2.Enabled = False
List1.Enabled = False
Form1.MousePointer = 11
lngCurIdx = 0
Do
lngValueLen = 2000
strValue = String(lngValueLen, 0)
lngClassLen = 2000
strClass = String(lngClassLen, 0)
' Enumerate all the sub keys
lngResult = RegEnumKeyEx(lngKeyHandle, _
lngCurIdx, _
ByVal strValue, _
lngValueLen, _
0&, _
ByVal strClass, _
lngClassLen, _
lngTime)
' Increment the index of found keys
lngCurIdx = lngCurIdx + 1
If lngResult = ERROR_SUCCESS Then
' Trim the current key to its actual length
strResult = Left(strValue, lngValueLen)
' Eliminate case if the search is insensitive
blnMatch = False
strValue = strResult
If Check1.Value = 0 Then
strResult = LCase(strResult)
strSearch = LCase(strSearch)
End If
' Compare strings based upon search type
Select Case Combo2.ListIndex
Case 0
' Check if any portion of the search string is found.
If InStr(strResult, strSearch) Then blnMatch = True
Case 1
' Check if an exact match is found.
If strResult = strSearch Then blnMatch = True
Case 2
' Check if the search string matches the
' left portion of the key string.
If Left(strResult, intSearchLen) = strSearch Then blnMatch = True
Case Else
' Check if the search string matches the
' right portion of the key string.
If Right(strResult, intSearchLen) = strSearch Then blnMatch = True
End Select
' Populate the list with keys that match
' the search criteria
If blnMatch Then
i = i + 1
List1.AddItem strValue
End If
End If
' Keep looking for more keys
Loop While lngResult = ERROR_SUCCESS
' Close the Root Branch
lngResult = RegCloseKey(lngKeyHandle)
' Enable the buttons
Form1.MousePointer = 0
List1.Enabled = True
Command1.Enabled = True
Command2.Enabled = True
' Display the total matches
MsgBox "Total matches:" & Str(i), , "Search Registry Keys"
End If
End Sub
Private Sub Command2_Click()
Unload Me
End Sub
Private Sub Form_Load()
' Set up the Form interface
Form1.Caption = "Search Registry Keys"
Form1.Move 0, 0, 6960, 4230
Label1.Caption = "Search Branch:"
Label1.Move 240, 240, 1215, 255
Label2.Caption = "Search Mode:"
Label2.Move 240, 720, 1215, 255
Label3.Caption = "Find What:"
Label3.Move 240, 1200, 1215, 255
Combo1.Move 1680, 240, 2535
Combo1.AddItem "HKEY_CLASSES_ROOT"
Combo1.AddItem "HKEY_CURRENT_USER"
Combo1.AddItem "HKEY_LOCAL_MACHINE"
Combo1.AddItem "HKEY_USERS"
Combo1.ListIndex = 0
Combo1.TabIndex = 0
Combo2.Move 1680, 720, 2535
Combo2.AddItem "Portion"
Combo2.AddItem "All"
Combo2.AddItem "Left"
Combo2.AddItem "Right"
Combo2.ListIndex = 0
Combo2.TabIndex = 1
Text1.Move 1680, 1200, 2535, 350
Text1.Text = ""
Text1.TabIndex = 2
Command1.Caption = "Find Keys"
Command1.Move 4560, 240, 1935, 375
Command1.TabIndex = 3
Command1.Default = True
Command2.Caption = "Close"
Command2.Move 4560, 720, 1935, 375
Command2.TabIndex = 4
Check1.Caption = "Match Case"
Check1.Move 4680, 1320, 1275, 255
Check1.TabIndex = 5
List1.Move 240, 1920, 6255, 1620
List1.TabIndex = 6
End Sub
6. Run the project and execute a search. Note that Keys that match the search
criteria are displayed in the ListBox.
REFERENCES
==========
For more information the Registry API functions, please search on the following
topics in either the Win32 Programmer's Reference or the Microsoft Developer
Network (MSDN) Library CD-ROM:
- RegCloseKey
- RegEnumKeyEx
- RegOpenKeyEx
For additional information, click the article number below to view the article in
the Microsoft Knowledge Base:
Q145679 HOWTO: Use the Registry API to Save and Retrieve Setting
Additional query words: win32 winapi
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Keywords : kbAPI kbRegistry kbSDKWin32 kbVBp kbVBp500 kbVBp600 kbGrpDSVB kbDSupport kbCodeSnippet
Technology : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500 kbVBA600 kbVB500 kbVB600
Version : WINDOWS:5.0,6.0
Issue type : kbhowto
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