Knowledge Base

How To Determine the Version of DCOM 95/98 Using Visual Basic

Article ID: 232003

Article Last Modified on 7/1/2004

APPLIES TO

Microsoft Visual Basic 5.0 Learning Edition
Microsoft Visual Basic 6.0 Learning Edition
Microsoft Visual Basic 5.0 Professional Edition
Microsoft Visual Basic 6.0 Professional Edition
Microsoft Visual Basic 5.0 Enterprise Edition
Microsoft Visual Basic 6.0 Enterprise Edition

This article was previously published under Q232003

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:

Start a new Visual Basic Standard EXE project. Form1 is created by default.
Add a CommandButton (Command1) to Form1.

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

Run the program and click Command1. Result: If DCOM is installed on the system, the message box will display the version number.

Notes:

The function DCOMEnabled may be used separately to determine if DCOM has been installed on a system without checking for the version.

It is not necessary to test for DCOM on Windows NT 4.0 or Windows 2000 because it is already installed. (See REFERENCES below.)

The most current version of DCOM for Windows 95 and 98 might be downloaded from:

http://www.microsoft.com/com/resources/downloads.asp

REFERENCES

For additional information about DCOM, please see the following:

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

For additional information, click the article numbers below to view the articles in the Microsoft Knowledge Base:

266717 How To Create a DCOM Client/Server Application by Using Visual Basic

267836 How To Create a DCOM Client/Server with Events by Using Visual Basic

268550 How To Use Dcomcnfg for a Visual Basic DCOM Client/Server Application

269330 How To Troubleshoot DCOM for Visual Basic Client/Server Applications

For information about programmatically determining the OS, please see the following article in the Microsoft Knowledge Base:

189249 How To Determine Which 32-Bit Windows Version Is Being Used

Keywords: kbhowto kbregistry kbapi kbdcom KB232003

Microsoft KB Archive/232003

Contents

How To Determine the Version of DCOM 95/98 Using Visual Basic

SUMMARY

MORE INFORMATION

REFERENCES