Using WaitForExit() causes my program to hang

Question

Using WaitForExit() causes my program to "hang" at this statement.
Without the WaitForExit() my program competes under 1 minute.
Please check my code below and let me know what I am doing incorrectly.

Dim m_oProc As New Process
Dim oInfo As ProcessStartInfo

oInfo = New ProcessStartInfo("some.wsf", sArgs)
oInfo.UseShellExecute = False
oInfo.RedirectStandardOutput = True
oInfo.RedirectStandardError = True
oInfo.CreateNoWindow = True
m_oProc.StartInfo = oInfo

Dim et As New StdErrorThread(m_oProc)
Dim t As New Thread(AddressOf et.ThreadProc)
et.ErrLogObj = ErrLogObj

If m_oProc.Start() Then
   t.Start()
   m_oProc.WaitForExit()
...

Without the WaitForExit the "some.wsf" file completes within a minute.
With the WaitForExit the script does not complete and my code hangs.

Why?

If I use WaitForExit(30000) then execution continues on the next line only AFTER 5 minutes!

Why?

 

Answer 1

... correction to my comment above, the "WaitForExit(30000)" should read "WaitForExit(300000)"!

Answer 2

Hello Siggy01

In which thread are you calling m_oProc.WaitForExit()? Is it the WinForm UI thread? If yes, please move the call to a worker thread. It's not recommended to wait in UI thread for I/O or external applications that may take a long time.

---

Regards,
Jialiang Ge
MSDN Subscriber Support in Forum
If you have any feedback of our support, please contact [e-mail].
Please remember to mark the replies as answers if they help and unmark them if they provide no help.
Welcome to the All-In-One Code Framework! If you have any feedback, please tell us.

Answer 3

You are redirecting output but there's no evidence that you are actually reading the output.  Doing it after the WaitForExit() call is usually too late.  The redirected app's output buffer will fill up and then it will block, waiting for somebody to empty the buffer.  Use BeginOutputReadLine() to avoid this.

---

Hans Passant.

Answer 4

Hello Siggy01

How are you? Do you get any progress in the issue? If you have any other questions, please feel free to post here.

---

Regards,
Jialiang Ge
MSDN Subscriber Support in Forum
If you have any feedback of our support, please contact [e-mail].
Please remember to mark the replies as answers if they help and unmark them if they provide no help.
Welcome to the All-In-One Code Framework! If you have any feedback, please tell us.

Answer 5

Hi Jialiang,

Thanks for your response and sorry about the delayed response from me.

I have now created a separate thread for the stdout as well as the stderr. 
So in effect I have the main thread plus a thread for each of the 2 results that I am receiving.
The WaitForExit is being executed on the main thread and all is working as it should.

Once again thanks for pointing me in the correct direction.

Regards
Siggy