HOWTO: Enumerate 16-bit Tasks on Window NT Using Visual Basic

• Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, versions 5.0, 6.0
  on the following platforms: NT

SUMMARY

There may be times when it is necessary to enumerate all of the 16-bit tasks that are running on a Windows NT system. To do this you use the VDMEnumProcessWOW and VDMEnumTaskWOWEx API functions. The MORE INFORMATION has an example of using these functions within Visual Basic. Note, that it is also necessary to use call back functions to enumerate the 16-bit processes. If you are unfamiliar with the use of callback functions from within Visual Basic, see the article referenced in the REFERENCES section of this article.

MORE INFORMATION

Steps to Create the Example

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



2. Add one CommandButton to the form.



3. Set the forms AutoReDraw property to True.



4. Select Project from the Menu and add a new module to the project. Module1 is created by default.



5. Copy the following code into the Code window of Module1:




Option Explicit

Declare Function VDMEnumProcessWOW Lib "VDMDBG.dll" _ 
(ByVal fp As Long, lparam As Long) As Integer 

Declare Function VDMEnumTaskWOWEx Lib "VDMDBG.dll " _ 
(dwProcessId As Long, ByVal fp As Long, lparam As Long) As Integer 

Declare Function lstrcpy Lib "kernel32" _ 
(ByVal lpString1 As Any, ByVal lpString2 As Any) As Long 

Public Function PROCESSENUMPROC _
(ByVal dwProcessId As Long, ByVal dwAttributes As Long, _
lpUserDefined As Long) As Boolean
  
    Form1.Cls
    Form1.Print "dwProcessId: " & dwProcessId
    Form1.Print "dwAttributes: " & dwAttributes & vbCrLf 
' Pass the Process ID to this next function to enumerate that Process.
    Call VDMEnumTaskWOWEx(ByVal dwProcessId, AddressOf TASKENUMPROCEX, 0)

End Function

Public Function TASKENUMPROCEX _ 
(ByVal dwThreadId As Long, ByVal hMod16 As Long, _ 
ByVal hTask16 As Long, ByVal pszModName As Long, _ 
ByVal pszFileName As Long, lpUserDefined As Long) As Boolean 

' Print Enumerated task of the 16bit process
    Form1.Print "dwThreadId: " & dwThreadId & vbCrLf & _
    "hMod16: " & hMod16 & vbCrLf & "hTask16: " & hTask16 & vbCrLf & _
    "pszModName: " & PointerToString(pszModName) & vbCrLf & _
    "pszFileName: " & PointerToString(pszFileName) & vbCrLf & _
    "lpUserDefined: " & lpUserDefined & vbCrLf
' Return value is false until there are no more tasks to enumerate.  
End Function

Private Function PointerToString(lPtr As Long) As String
Dim sTemp As String * 255, Retval As Long
' Parse String Values returned from function call. 

    Retval = lstrcpy(sTemp, lPtr)
    If (InStr(1, sTemp, Chr(0)) = 0) Then
         PointerToString = ""
    Else
         PointerToString = Left(sTemp, InStr(1, sTemp, Chr(0)) - 1)
    End If
    
End Function 

6. Copy the following code into the Code window of Form1:




Private Sub Command1_Click() 

Dim Retval As Long 
' Call VDMEnumProcessWOW to beging the enumeration
   Retval = VDMEnumProcessWOW(AddressOf PROCESSENUMPROC, 0)

End Sub  

7. Save the Project and then press F5 to run the project. The enumerated processes will list on the form.

REFERENCES

Q170570 HOWTO: Build a Windows Message handler with Addressof in VB

Q181578 HOWTO: CallBack Visual Basic Functions From a C Dll

Additional query words:

Keywords : kbAPI kbNTOS400 kbSDKWin32 kbVBp kbVBp500 kbVBp600 kbGrpVB kbDSupport
Version : WINDOWS:5.0,6.0
Platform : WINDOWS
Issue type : kbhowto