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Make Your VB App Wait Tip


Derek E. Brown sends in this tip that should be very useful in a number of situations that can arise. The tip involves making a VB app wait for the completion of some other process outside VB. While Derek has a specific purpose in mind for this one, it should be fairly easy to modify for a number of different situations.

I found this to be an extremely useful piece of code for running an application from within VB and having the VB app wait until the outside process is complete. I have a program that has to wait until an uploaded zip file is unzipped before continued processing can take place. The code below involves a few API's, and though it's rather long and involved, I have yet to get an error using it.

'Windows API/Global Declarations for :Un'zipper
Private Const ZIPSIG = &H4034B50
Private Const ziputil = "c:\Program Files\PKUnzip\Pkzip25.exe"
Private Const SYNCHRONIZE = &H100000
'API's to monitor the status of Pkzip

Private Declare Function OpenProcess Lib "kernel32" (ByVal DesiredAccess As Long, _ ByVal bInheritHandle As Long, ByVal ProcessId As Long) As Long

Private Declare Function WaitForSingleObject Lib "kernel32" (ByVal hHandle
As Long, _ ByVal Milliseconds As Long) As Long Private Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long) As Long 

Private Type ZFHeader 
Signature As Long 
End Type

Private Sub sb_WaitForTemination(RetVl As Integer)

On Error Goto ErrorHandler:

Dim phnd&

phnd = OpenProcess(SYNCHRONIZE, 0, RetVl)

If phnd <> 0 Then
  Call WaitForSingleObject(phnd, INFINITE)
  Call CloseHandle(phnd)
End If

Exit Sub

  Err.Source = "sb_WaitForTermination in class Unzip in UnZipper"
  'Do Error Stuff Here
  Resume Next
End Sub

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Last modified: January 31, 2002