I am trying to enumerate the users of a system from within my app (VB.NET) Not finding any .Net Framework classes to do this I turned to the Win32 API and NetQueryDisplayInformation. I can't get it to work from within VB.NET however. I found the following KB article from MS
http://support.microsoft.com/default...b;en-us;316318
When I try to convert to .Net I get an object reference not set error when calling the actual API function....Please help...
Here's my code:
Public Class UserList
'/* definitions and declarations
Private Const NET_USER = 1
Private Const NET_MACHINE = 2|
Private Const NET_GROUP = 3
Private Const ERROR_MORE_DATA = 234
Private Const REQUESTED_ENTRIES = 5
Private Const MAX_PREFERRED_LENGTH = -1
Private lResult As Int32
Private Structure NET_DISPLAY_USER
Dim usri1_name As Int32 'lpwstr
Dim usri1_comment As Int32 'lpwstr
Dim usri1_flags As Int32
Dim usri1_full_name As Int32 'lpwstr
Dim usri1_user_id As Int32
Dim usri1_next_index As Int32
End Structure
Private Structure NET_DISPLAY_GROUP
Dim grpi3_name As Int32 'lpwstr
Dim grpi3_comment As Int32 'lpwstr
Dim grpi3_group_id As Int32
Dim grpi3_attributes As Int32
Dim grpi3_next_index As Int32
End Structure
Private Structure NET_DISPLAY_MACHINE
Dim usri2_name As Int32 'lpwstr
Dim usri2_comment As Int32 'lpwstr
Dim usri2_flags As Int32
Dim usri2_user_id As Int32
Dim usri2_next_index As Int32
End Structure
Private Declare Function NetQueryDisplayInformation Lib "netapi32.dll" ( _
ByVal lpwServername As String, _
ByVal dwLevel As Int32, _
ByVal dwIndex As Int32, _
ByVal dwReqEntries As Int32, _
ByVal dwMaxLength As Int32, _
ByVal pdwNumEntries As Int32, _
ByVal pBuffer As Int32) As Int32
Private Declare Function NetApiBufferFree Lib "netapi32.dll" (ByVal BufPtr As Int32) As Int32
Private Declare Sub CopyMem Lib "KERNEL32" Alias "RtlMoveMemory" ( _
ByVal hpvDest As Int32, ByVal hpvSource As Int32, ByVal cbCopy As Int32)
Private Declare Function CopyString Lib "KERNEL32" Alias "lstrcpyW" ( _
ByVal NewString As String, ByVal OldString As Int32) As Int32
Public Sub GetUserNames()
Try
'/* This code enumerates domain users.
Dim pndu() As NET_DISPLAY_USER
Dim pszTemp As String, pszServer As String
Dim pBuffer As Int32
Dim lLevel As Int32
Dim lIndex As Int32
Dim lNumEntries As Int32
Dim lTotalEntries As Int32
pszServer = ""
lIndex = 0
lTotalEntries = 0
lNumEntries = 0
lResult = ERROR_MORE_DATA
'************************************************* ***************************************
'Here's where I get the object reference not set to an instance of an object error
lResult = NetQueryDisplayInformation(pszServer, NET_USER, lIndex, _
REQUESTED_ENTRIES, MAX_PREFERRED_LENGTH, lNumEntries, pBuffer)
'************************************************* ***************************************
Catch ex As Exception
Throw New ApplicationException(ex.Message, ex)
End Try
End Sub
End Class
