SetParent acting funny

[Piller187]

I have this small chunk of code in an MDI form. When I press a menu item it does this:

        Me.SuspendLayout()
        Dim runProcess As New System.Diagnostics.Process
        Dim info As New System.Diagnostics.ProcessStartInfo

        info.FileName = "NotePad.exe"
        info.WindowStyle = ProcessWindowStyle.Normal

        runProcess = Process.Start(info)

        SetParent(runProcess.MainWindowHandle, Me.Handle)

        Me.ResumeLayout()

The idea is to have a totally seperate program run inside an MDI for. If I just run this code it doesn't work. However, if I put a break point on the SetParent, and when it goes there F5 to continue it then works. It's almost like a timing thing. Like SetParent() can't set it right away. Does anyone have any advise? Putting any sort of sleep or wait really wouldn't be a great solution. This just seems very strange to me. Thanks in advance.

 

[Piller187]

I did this little check and it appears Start doesn't wait until the process has a handle, cause the messagebox comes up.

 Me.SuspendLayout()
        Dim runProcess As New System.Diagnostics.Process
        Dim info As New System.Diagnostics.ProcessStartInfo

        info.FileName = "NotePad.exe"
        info.WindowStyle = ProcessWindowStyle.Normal

        runProcess = Process.Start(info)

        If runProcess.MainWindowHandle <> 0 Then
            SetParent(runProcess.MainWindowHandle, Me.Handle)
        Else
            MsgBox("No window handle")
        End If

        Me.ResumeLayout()

 

[Piller187]

That doesn't work either. The only way I get a non 0 handle is if I step through the code. This doesn't make any sense.

 

[JohnH]

What if you waited 1 second with 'WaitForInputIdle(1000)' then 'SetParent' ? Worth a try perhaps, maybe when step-through there is a little more time for the other process to load it's main window..

 

[Piller187]

Yeah I did:

System.Threading.Thread.Sleep(500)

and that works but I don't like the solution. Kind of hacky.

 

[JohnH]

Well, use the overload that waits indefinitely, but only until other process is loaded. Does also jump out if it is not a 'valid' process. This is not hacky.

If runProcess.WaitForInputIdle = True Then
  SetParent(runProcess.MainWindowHandle, Me.Handle)
Else
  'immediately returned False, process didn't have a message loop
  '(because it didn't have an user interface)
  MsgBox("No window handle")
End If

 

[Piller187]

That actually doesn't work for non user interface programs. Try it with cmd in .NET 2005. I know every process that is getting started so I won't run into this. Thanks.