HOWTO: Determine the Version of DCOM 95/98 Using Visual Basic

• Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, versions 5.0, 6.0

SUMMARY

The version of DCOM95 or DCOM98 installed on a Windows 9x system may be determined by checking the registry using Visual Basic. If DCOM is installed on the system, the default value of the registry key:

HKCR\CLSID\{bdc67890-4fc0-11d0-a805-00aa006d2ea4}\InstalledVersion

will contain the version of DCOM installed on the system. The version number in the registry is stored in the format "a,b,c,d", where a, b, c, and d are numeric values. These values form the version number of the DCOM install:

InstalledVersion	DCOM Version
"4,71,0,3328"	DCOM95 and DCOM98 1.3 4.71.0.3328
"4,71,0,2618"	DCOM95 1.2 Web Release 4.71.0.2618
"4,71,0,2612"	DCOM 1.2 4.71.0.2612 DCOM98.exe shipped with VS6.0
"4,71,0,1719"	DCOM Win98 Gold 4.71.0.1719
"4,71,0,1718"	DCOM95 1.1 4.71.0.1718
"4,71,0,1120"	DCOM 1.x 4.71.0.1120

MORE INFORMATION

The following steps outline this process from Visual Basic:

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



2. Add a CommandButton (Command1) to Form1.



3. Add the following code to the General Declarations section of Form1:




Option Explicit

Private Const ERROR_SUCCESS = 0&

Private Const HKEY_LOCAL_MACHINE = &H80000002
Private Const HKEY_CLASSES_ROOT = &H80000000

Private Const STANDARD_RIGHTS_ALL = &H1F0000
Private Const KEY_QUERY_VALUE = &H1
Private Const KEY_SET_VALUE = &H2
Private Const KEY_CREATE_SUB_KEY = &H4
Private Const KEY_ENUMERATE_SUB_KEYS = &H8
Private Const KEY_NOTIFY = &H10
Private Const KEY_CREATE_LINK = &H20
Private Const SYNCHRONIZE = &H100000

Private Const KEY_ALL_ACCESS = _
   ((STANDARD_RIGHTS_ALL Or _
     KEY_QUERY_VALUE Or _
     KEY_SET_VALUE Or _
     KEY_CREATE_SUB_KEY Or _
     KEY_ENUMERATE_SUB_KEYS Or _
     KEY_NOTIFY Or _
     KEY_CREATE_LINK _
    ) _
    And (Not SYNCHRONIZE) _
   )

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 RegCloseKey Lib _
   "advapi32.dll" _
   (ByVal hKey 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, _
    ByVal lpData As String, _
    lpcbData As Long) _
   As Long
   
' Note that if you declare the lpData
' parameter as String, you must pass it
' By Value as is done here.

Private Declare Function GetProcAddress _
   Lib "kernel32" _
   (ByVal hModule As Long, _
    ByVal lpProcName As String) _
   As Long

Private Declare Function GetModuleHandle _
   Lib "kernel32" Alias "GetModuleHandleA" _
   (ByVal lpModuleName As String) _
   As Long
   
Private Function DCOMEnabled() As Boolean
' We need to check two things
' 1- OLE32 supports free threading
' 2- DCOM is enabled in the registry
' See Inside COM, Rogerson, pp 276-277

   DCOMEnabled = False
   
' First, check to see if OLE32 supports free threading.
' You need to check for the CoInitializeEx function's
' presence in OLE32.
' 1- Get a handle to the OLE32 module
' 2- Try to get a ProcAddress for CoInitializeEx

   Dim OLE32ModuleHandle As Long
   Dim CoInitializeExProcAddress As Long
   
   OLE32ModuleHandle = GetModuleHandle("OLE32")
   Debug.Assert (Not OLE32ModuleHandle = 0)
   
   CoInitializeExProcAddress = GetProcAddress( _
           OLE32ModuleHandle, _
           "CoInitializeEx")
         
   Debug.Print "CoInitializeExProcAddress = " _
               & CoInitializeExProcAddress
               
   If CoInitializeExProcAddress = 0 Then
      DCOMEnabled = False
      Exit Function
   End If
   
' Now check the registry to see if DCOM is enabled.
   
   Dim lResult As Long
   Dim hKey As Long

   lResult = RegOpenKeyEx(HKEY_LOCAL_MACHINE, _
                   "SOFTWARE\Microsoft\Ole", _
                   0, _
                   KEY_ALL_ACCESS, _
                   hKey)
   
   Debug.Assert (lResult = ERROR_SUCCESS)

   Dim rgch As String
   rgch = String(2, 0)
   
   Dim cbrgch As Long
   cbrgch = Len(rgch)
   
   lResult = RegQueryValueEx(hKey, "EnableDCOM", 0, 0&, rgch, cbrgch)

   Debug.Assert (lResult = ERROR_SUCCESS)

   Debug.Print "Mid$(rgch, 1) is " & Mid$(rgch, 1)

   If (Mid$(rgch, 1, 1) = "Y" Or Mid$(rgch, 1, 1) = "y") Then
      ' DCOM is Enabled
      DCOMEnabled = True
   Else
      DCOMEnabled = False
   End If
                   
   lResult = RegCloseKey(hKey)
           
End Function

Public Function GetDCOMVersion() As String
    ' Check the registry key "InstalledVersion" to see which
    ' version of DCOM is installed.

   Dim hKey As Long
   Dim lResult As Long

' First confirm that DCOM is installed
   If Not DCOMEnabled() Then
       MsgBox "Can't check version.  DCOM is not installed."
       Exit Function
   End If

' open the the proper registry key
   lResult = RegOpenKeyEx(HKEY_CLASSES_ROOT, _
         "CLSID\{bdc67890-4fc0-11d0-a805-00aa006d2ea4}\InstalledVersion", _
         0, _
         KEY_ALL_ACCESS, _
         hKey)

   If Not lResult = ERROR_SUCCESS Then
       MsgBox "Could not open registry key"
       Exit Function
   End If

   Dim rgch As String
   rgch = String(64, 0)

   Dim cbrgch As Long
   cbrgch = Len(rgch)

   lResult = RegQueryValueEx(hKey, "", 0, 0&, rgch, cbrgch)

   lResult = RegCloseKey(hKey)

   Dim temp As String

   temp = Mid$(rgch, 1, cbrgch)

   GetDCOMVersion = temp

End Function

Private Sub Command1_Click()
   MsgBox GetDCOMVersion()
End Sub 

4. Run the program and click Command1.


Result: If DCOM is installed on the system, the message box will display the version number.

REFERENCES

For additional information about DCOM, please see the following:

"Inside COM", Dale Rogerson, c1997 Microsoft Press pp. 276-277

Q175510 FILE: VB5DCOM.EXE: Using Callbacks and WithEvents with DCOM

Q189249 HOWTO: Determine Which 32-Bit Windows Version Is Being Used

© Microsoft Corporation 1999, All Rights Reserved.
Contributions by Gray McDonald, Microsoft Corporation

Additional query words:

Keywords : kbAPI kbDCOM kbRegistry kbSDKWin32 kbVBp kbVBp500 kbVBp600 kbGrpVB
Version : WINDOWS:5.0,6.0
Platform : WINDOWS
Issue type : kbhowto