HOWTO: Enumerate the Values of a Registry Key

• Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, version 5.0

SUMMARY

The RegEnumValue API function allows you to enumerate the values of a registry key. Program settings are commonly stored in the registry. Enumerating through a registry key enables you to read the registry settings of a program so that you can restore the settings the next time you start the program.

This article shows you how to use the RegEnumValue function to enumerate the values of a registry key.

MORE INFORMATION

The following is the Visual Basic declaration statement for RegEnumValue:

   Private Declare Function RegEnumValue Lib "advapi32.dll" _
                   Alias "RegEnumValueA" _
                   (ByVal hKey As Long, _
                   ByVal dwIndex As Long, _
                   ByVal lpValueName As String, _
                   lpcbValueName As Long, _
                   ByVal lpReserved As Long, _
                   lpType As Long, _
                   lpData As Any, _
                   lpcbData As Long) As Long

   ARTICLE-ID: Q173009
   TITLE     : PRB: Runtime Error 87 Using RegEnumValue Function

Step-by-Step Example

1. Start a new Standard EXE project in Visual Basic. Form1 is created by default.

2. Add a CommandButton and a ListBox Control to Form1. Because many of the entries are lengthy, you should ListBox extend your across the full width of the form.

3. Copy the following code to the Code window of Form1:

         Option Explicit
   

         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 RegEnumValue Lib "advapi32.dll" _
             Alias "RegEnumValueA" _
             (ByVal hKey As Long, _
             ByVal dwIndex As Long, _
             ByVal lpValueName As String, _
             lpcbValueName As Long, _
             ByVal lpReserved As Long, _
             lpType As Long, _
             lpData As Any, _
             lpcbData As Long) 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 STANDARD_RIGHTS_WRITE = &H20000
         Const STANDARD_RIGHTS_EXECUTE = &H20000
         Const STANDARD_RIGHTS_REQUIRED = &HF0000
         Const STANDARD_RIGHTS_ALL = &H1F0000
         Const KEY_QUERY_VALUE = &H1
         Const KEY_SET_VALUE = &H2
         Const KEY_CREATE_SUB_KEY = &H4
         Const KEY_ENUMERATE_SUB_KEYS = &H8
         Const KEY_NOTIFY = &H10
         Const KEY_CREATE_LINK = &H20
         Const KEY_READ = ((STANDARD_RIGHTS_READ Or _
                           KEY_QUERY_VALUE Or _
                           KEY_ENUMERATE_SUB_KEYS Or _
                           KEY_NOTIFY) And _
                           (Not SYNCHRONIZE))
   
         Const REG_DWORD = 4
         Const REG_BINARY = 3
         Const REG_SZ = 1
         Private Sub Command1_Click()
            Dim lngKeyHandle As Long
            Dim lngResult As Long
            Dim lngCurIdx As Long
            Dim strValue As String
            Dim lngValueLen As Long
            Dim lngData As Long
            Dim lngDataLen As Long
            Dim strResult As String
   
            lngResult = RegOpenKeyEx(HKEY_LOCAL_MACHINE, _
                    "SOFTWARE\Microsoft\Windows\CurrentVersion\SharedDlls", _
                     0&, _
                     KEY_READ, _
                     lngKeyHandle)
   
            If lngResult <> ERROR_SUCCESS Then
                MsgBox "Cannot open key"
                Exit Sub
            End If
   
            lngCurIdx = 0
            Do
               lngValueLen = 2000
               strValue = String(lngValueLen, 0)
               lngDataLen = 2000
   
               lngResult = RegEnumValue(lngKeyHandle, _
                                        lngCurIdx, _
                                        ByVal strValue, _
                                        lngValueLen, _
                                        0&, _
                                        REG_DWORD, _
                                        ByVal lngData, _
                                        lngDataLen)
               lngCurIdx = lngCurIdx + 1
   
            If lngResult = ERROR_SUCCESS Then
               strResult = lngCurIdx & ": " & Left(strValue, lngValueLen)
               List1.AddItem strResult
            End If
   
            Loop While lngResult = ERROR_SUCCESS
            Call RegCloseKey(lngKeyHandle)
         End Sub
   
   

4. On the Run menu, click Start or press the F5 key to start the program. Click the CommandButton. All the values for the registry key HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\SharedDlls are displayed in the list box.

REFERENCES

For additional information about using Visual Basic to manipulate registry settings, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q172274
   TITLE     : INFO: Using the Registry API to Save and Retrieve Settings