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Determining if DCOM is installe



Determining if DCOM is installe

The following function determines if DCOM is installed on the local machine:

Option Explicit
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 GetModuleHandle Lib "kernel32" Alias "GetModuleHandleA" (ByVal lpModuleName As String) As Long
Private Declare Function GetProcAddress Lib "kernel32" (ByVal hModule As Long, ByVal lpProcName As String) As Long
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 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 STANDARD_RIGHTS_ALL = &H1F0000
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 Const ERROR_SUCCESS = 0

'Purpose   :    Determines if DCOM (Distributed Component Object Model) is installed and enabled on the current machine.
'Inputs    :    N/A
'Outputs   :    Returns True if DCOM is available.


Function DCOMInstalled() As Boolean
    Const HKEY_LOCAL_MACHINE = &H80000002
    Dim bPresent As Boolean
    Dim bEnabled As Boolean
    Dim hKey As Long
    Dim lpType As Long
    Dim lpData
    Dim lResult As Long
    Dim lpcbData As Long

    'Check to see if OLE32 supports free threading, by checking
    'for the CoInitializeEx function's presence in OLE32:
    '1. Get a handle to the OLE32 module
    '2. Try to get a ProcAddress for CoInitializeEx
    
    lResult = GetProcAddress(GetModuleHandle("OLE32"), "CoInitializeEx")
    If lResult <> 0 Then
        'OLE32 supports free threading
        bPresent = True
    Else
        'OLE32 doesn 't support free threading
        bPresent = False
    End If
    
    'Check the registry to see if DCOM is enabled
    lResult = RegOpenKeyEx(HKEY_LOCAL_MACHINE, "SOFTWARE\Microsoft\Ole", 0, KEY_ALL_ACCESS, hKey)
    lpcbData = Len("EnableDCOM")    '10
    
    If lResult = ERROR_SUCCESS Then
        lResult = RegQueryValueEx(ByVal hKey, "EnableDCOM", 0, ByVal lpType, lpData, lpcbData)
    End If
    
    If lResult = ERROR_SUCCESS Then
        bEnabled = True
        RegCloseKey hKey
    Else
        bEnabled = False
    End If
    
    If bEnabled And bPresent Then
        DCOMInstalled = True
    Else
        DCOMInstalled = False
    End If
End Function