VB6: Writing to registry

Question

I have to edit an old legacy VB6 application so that it can edit the registry to write the following:

reg add "HKCU\Software\Microsoft\Print\UnifiedPrintDialog" /v "PreferLegacyPrintDialog" /d 1 /t REG_DWORD /f

How can I emulate the above command in VB6?

I read a few posts using the registry = CreateObject("WScript.shell") methodology but it doesn't seem clear to me and I really don't want to mess around with the registry without knowing what I'm doing. Otherwise, could I just run the command through a ShellExecute or something similar?

Any assistance would be appreciated. Thanks!

Answer 1

You can use the Windows API to accomplish what you need. Here's some general purpose code to read and write to the Registry:

Option Explicit

Private Sub Read_Click()
   Text1.Text = ReadRegistry(HKEY_CURRENT_USER, "Software\Microsoft\Print\UnifiedPrintDialog", "PreferLegacyPrintDialog", ValDWord, "1")
End Sub

Private Sub Write_Click()
   WriteRegistry HKEY_CURRENT_USER, "Software\Microsoft\Print\UnifiedPrintDialog", "PreferLegacyPrintDialog", ValDWord, Text1.Text
End Sub

In a Module place the following code:

Option Explicit

Public Const HKEY_CLASSES_ROOT = &H80000000
Public Const HKEY_CURRENT_USER = &H80000001
Public Const HKEY_LOCAL_MACHINE = &H80000002
Public Const HKEY_USERS = &H80000003
Public Const HKEY_PERFORMANCE_DATA = &H80000004

Public Const REG_SZ = 1
Public Const REG_DWORD = 4

Public Enum InTypes
   ValNull = 0
   ValString = 1
   ValXString = 2
   ValBinary = 3
   ValDWord = 4
   ValLink = 6
   ValMultiString = 7
   ValResList = 8
End Enum

Private Const ERROR_SUCCESS = 0&

Private Declare Function RegCloseKey Lib "advapi32.dll" (ByVal hKey As Long) As Long
Private Declare Function RegCreateKey Lib "advapi32.dll" Alias "RegCreateKeyA" (ByVal hKey As Long, ByVal lpSubKey As String, phkResult As Long) As Long
Private Declare Function RegOpenKey Lib "advapi32.dll" Alias "RegOpenKeyA" (ByVal hKey As Long, ByVal lpSubKey As String, phkResult As Long) As Long
Private Declare Function RegQueryValueEx Lib "advapi32.dll" Alias "RegQueryValueExA" (ByVal hKey As Long, ByVal lpValueName As String, ByVal lpReserved As Long, lpType As Long, lpData As Any, lpcbData As Long) As Long
Private Declare Function RegSetValueEx Lib "advapi32.dll" Alias "RegSetValueExA" (ByVal hKey As Long, ByVal lpValueName As String, ByVal Reserved As Long, ByVal dwType As Long, lpData As Any, ByVal cbData As Long) As Long

Public Function ReadRegistry(ByVal Group As Long, ByVal Section As String, ByVal Key As String, ByVal ValType As InTypes, Optional Default As Variant) As Variant
   If ValType = ValString Then
      ReadRegistry = ReadString(Group, Section, Key)
      If ReadRegistry = "" Then ReadRegistry = Default
   ElseIf ValType = ValDWord Then
      ReadRegistry = ReadDword(Group, Section, Key)
      If ReadRegistry = 0 Then ReadRegistry = Default
   End If
End Function

Public Sub WriteRegistry(ByVal Group As Long, ByVal Section As String, ByVal Key As String, ByVal ValType As InTypes, ByVal Value As Variant)
   If ValType = ValString Then
      WriteString Group, Section, Key, CStr(Value)
   ElseIf ValType = ValDWord Then
      WriteDword Group, Section, Key, CLng(Value)
   End If
End Sub

Private Function ReadString(hKey As Long, strPath As String, strValue As String) As String
   Dim keyhand As Long
   Dim lResult As Long
   Dim strBuf As String
   Dim lDataBufSize As Long
   Dim intZeroPos As Integer
   Dim lValueType As Long
   Dim r As Long
   
   r = RegOpenKey(hKey, strPath, keyhand)
   lResult = RegQueryValueEx(keyhand, strValue, 0&, lValueType, ByVal 0&, lDataBufSize)
   strBuf = String(lDataBufSize, " ")
   lResult = RegQueryValueEx(keyhand, strValue, 0&, 0&, ByVal strBuf, lDataBufSize)
    
   If lResult = ERROR_SUCCESS Then
      intZeroPos = InStr(strBuf, Chr$(0))
        
      If intZeroPos > 0 Then
         ReadString = Left$(strBuf, intZeroPos - 1)
      Else
         ReadString = strBuf
      End If
   End If
End Function

Private Sub WriteString(hKey As Long, strPath As String, strValue As String, strdata As String)
   Dim keyhand As Long
   Dim r As Long
     
   r = RegCreateKey(hKey, strPath, keyhand)
   r = RegSetValueEx(keyhand, strValue, 0, REG_SZ, ByVal strdata, Len(strdata))
   r = RegCloseKey(keyhand)
End Sub

Private Function ReadDword(ByVal hKey As Long, ByVal strPath As String, ByVal strValueName As String) As Long
   Dim lResult As Long
   Dim lValueType As Long
   Dim lBuf As Long
   Dim lDataBufSize As Long
   Dim r As Long
   Dim keyhand As Long
   
   r = RegOpenKey(hKey, strPath, keyhand)
   
   lDataBufSize = 4
       
   lResult = RegQueryValueEx(keyhand, strValueName, 0&, lValueType, lBuf, lDataBufSize)
   
   If lResult = ERROR_SUCCESS Then
      If lValueType = REG_DWORD Then ReadDword = lBuf
   End If
   
   r = RegCloseKey(keyhand)
End Function

Private Sub WriteDword(ByVal hKey As Long, ByVal strPath As String, ByVal strValueName As String, ByVal lData As Long)
   Dim keyhand As Long
   Dim r As Long
     
   r = RegCreateKey(hKey, strPath, keyhand)
   r = RegSetValueEx(keyhand, strValueName, 0&, REG_DWORD, lData, 4)
   r = RegCloseKey(keyhand)
End Function

Answer 2

For "proper" registry access/read/write in VB6, you would need to implement the appropriate Win32 API methods. Here's a wrapper class for that. But for your simple need, the WScript.Shell approach should it (from the Windows Scripting Host helpfile):

RegWrite supports strType as REG_SZ, REG_EXPAND_SZ, REG_DWORD, and REG_BINARY. If another data type is passed as strType, RegWrite returns E_INVALIDARG.

RegWrite automatically converts anyValue to a string when strType is REG_SZ or REG_EXPAND_SZ. If strType is REG_DWORD, anyValue is converted to an integer. If strType is REG_BINARY, anyValue must be an integer.

Example
The following example writes a value and key entry into the registry:

Set WshShell = WScript.CreateObject("WScript.Shell")
WshShell.RegWrite "HKCU\ScriptEngine\Value", "Some string value"
WshShell.RegWrite "HKCU\ScriptEngine\Key\", 1 ,"REG_DWORD"