C# get window handle after starting a process

Question

Is there a way to get the window handle (IntPtr) for a window after its launched from a C# app with Process.Start()?

Process p = Process.Start("Notepad"); p.WaitForInputIdle(); SetParent(p.MainWindowHandle, CBox.Handle); — Ebrahim Karam
– Ebrahim Karam, Commented Mar 28, 2021 at 0:24

Noldorin · Accepted Answer · 2009-09-14 12:14:23Z

28

If it's the main window you're after, Process.MainWindowHandle will give you what you need.

answered Sep 14, 2009 at 12:14

Noldorin

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Jan Jongboom · Accepted Answer · 2009-09-14 12:15:35Z

9

Use

process.MainWindowHandle;

It probably is 0 when launching the app, so you might want to loop and sleep until it is filled up.

answered Sep 14, 2009 at 12:15

Jan Jongboom

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2 Comments

Marcel Over a year ago

Hi Jan, For me, the handle is always zero and never goes to any other value, even after infinite looping. I use the following code: proc.StartInfo.FileName = @"C:\Documents and Settings\SUM\Desktop\PortableApps\Notepad++Portable\Notepad++Portable.exe"; proc.StartInfo.Arguments = String.Empty; proc.Start(); IntPtr appHwnd = proc.MainWindowHandle; while (appHwnd == IntPtr.Zero) { Thread.Sleep(100); appHwnd = proc.MainWindowHandle; } What's wrong?

Marcel Over a year ago

According to this (xtremedotnettalk.com/…) it may also be zero because an application does show a dialog or initializing flash first.

Sam · Accepted Answer · 2016-05-16 13:49:27Z

7

This is not a recent topic but the answers are incomplete.

I agree with the Process.MainWindowHandle solution and to wait for the value but not with Sleep.

If you have just started a process and want to use its main window handle, consider using the WaitForInputIdle method to allow the process to finish starting, ensuring that the main window handle has been created.

Process.WaitForInputIdle

This overload applies only to processes with a user interface and, therefore, a message loop.

answered May 16, 2016 at 13:49

Sam

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4 Comments

Sri Harsha Chilakapati Over a year ago

I think this should actually be a comment.

Sam Over a year ago

i am sorry, for some reasons, this wait.... function throw the exception(there is only one), i will resolve with Sleep and Refresh

Grahamvs Over a year ago

The Process.WaitForInputIdle seems to return almost immediately if it's used on a WPF application. I believe this is due to the WPF internals...

DAG Over a year ago

It returns almost immediately for my .NET 4.5 application. Previous person said WPF, mine is just desktop application.

Tristan · Accepted Answer · 2009-09-14 13:05:22Z

3

You could also call Refresh() on the process to be sure the info in accurate

answered Sep 14, 2009 at 13:05

Tristan

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