using api in vb.net

using api in vb.net

• MarkOlbert

  I think just adding

  Sub WindowProc

  End Sub

  would work, hmm.

  Interesting code there, does it subclass another window Can you subclass windows in this way

  Ahmedilyas

  
  
  

• twolfkg

  by putting:
  "System.Threading.Thread.Sleep(1)"
  into the do loop before the "System.Windows.Forms.Application.DoEvents()", the program will run just fine.
  But will try the process class approach later.
  
  
  
  

• lachlanj

  that might be a solution, i will try it, thanks.
  
  

• ignitionflip

  You can override the windows messaging procedure as follows

  Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)

  MyBase.WndProc(m)

  End Sub

  Not sure if you actually need the delegate but here is the info....

  TO use a delegate:

  http://msdn.microsoft.com/library/default.asp url=/library/en-us/vblr7/html/vastmdelegate.asp

  Delegate Sub MyWinProc(ByRef m As System.Windows.Forms.Message)

  
  
  

• Philly10407

  actually "Address of " is from the VB6, it is not inserted by VB.NET, and now i think the delegate is not a problem as the program can go pass it...sorry, my mistake.. But another related problem occured..
  
  what happened is that this project is tring to launch a Fortran (executable) program at the back stage, then receive results from it, show them in the main form (say in a listbox). The project needs to use some windows APIs to achieve this task.
  
  The prosedure is outlined below:
  
  firstly, do the hooking:
  lpPrevWndProc = SetWindowLong(gWH, GWL_WNDPROC, AddressOf WindowProc)
  
  then, run the Fortran program:<Fortran program has been described in ShellExInfo structure>
  
  ShellExecuteEx(ShellExInfo)
  
  then use a do loop to 'catch' the messages from Fortran program, process it in WindowProc:
  dim wait as boolean
  If wait Then
  do
  System.Windows.Forms.Application.DoEvents()
  Call GetExitCodeProcess(ShellExInfo.hProcess, dwExitCode)
  Loop Until dwExitCode <> STILL_ACTIVE
  End If
  
  the problem is i have to put a break point at "System.Windows.Forms.Application.DoEvents()" to capture all the results from the program, if i remove that, only a couple lines of results will be returned, and then Visual studio will stop at that line and issue a warning: "A callback was made on a garbage collected delegate of type 'Project1!Project1.MsgReceive+SubClassProcDelegate::Invoke'. This may cause application crashes, corruption and data loss. When passing delegates to unmanaged code, they must be kept alive by the managed application until it is guaranteed that they will never be called.
  
  How should i do now
  
  
  Note: Part of the declaration is:
  
  Declare Function SetWindowLong Lib "USER32.DLL" Alias "SetWindowLongA" (ByVal hwnd As Integer, ByVal nIndex As Integer, ByVal dwNewLong As Integer) As Integer
  
  Delegate Function SubClassProcDelegate(ByVal hwnd As Integer, ByVal msg As Integer, ByVal wParam As Integer, ByVal lParam As Integer) As Integer
  
  Declare Function SetWindowLong Lib "USER32.DLL" Alias "SetWindowLongA" (ByVal hwnd As Integer, ByVal attr As Integer, ByVal lVal As SubClassProcDelegate) As Integer
  

• Pockey

  You DEFINATELY need to use the System.Diagnostics.Process class! Learn about it and it will make your life much easier, please!
  
  

• Andy Mil

  ShellExecuteEx(ShellExInfo)

  Have you tried upgrading the ShellExecuteEx method to the Process class...The process class allows io redirection and has a waitfor exit method to ensure that the process has completed before continuing in your code

  
  
  
• using api in vb.net