Howto convert Process.Handle to HWND

Question

5.00/5 (1 vote)

See more:

In interfacing some new .NET code to a legacy c++ application, I would find it very convenient to be able to convert the Process "Handle" to a proper Windows SDK HWND so I can make my .NET forms proper child windows of my legacy app. Anybody out there know how to do this?

using System.Runtime.InteropServices;

[DllImport("User32.dll")]
private static extern int SetParent(IntPtr hwndChild, IntPtr hwndParent);


void SetMyParent (IntPtr parentHwnd) {
   Process p = System.Diagnostics.Process.GetCurrentProcess();
   SetParent(p.Handle, parentHwnd); // this doesn't work!
}

I've tried several variations on this theme, all to no avail. I can make this work by using the User32.dll function to GetForegroundWindow() rather than p.Handle, but I can't guarantee that the window I launch will always be on top. I've managed to end up with Microsoft Outlook as my child window by trying that.

I don't understand why p.Handle isn't identical to an old fashioned HWND, and even if it isn't, why there isn't an easy conversion between the two types somewhere in InteropServices.

Thanks for any help on this!

Note: Thanks Chris, for your post (below). Granted, I have confused "process" with "window" here, but the legacy Windows SDK works almost exclusively with window handles, so if a single process has multiple windows, that still begs the question of how to enumerate them in .NET without resorting to FindWindow or EnumWindows. The problem with FindWindow is that it demands a class name, and when I examine .NET window class names, they seem to be constructed at runtime to be unique, but have little relation to the actual form class name. I'll look at the details of the link you gave to see if that provides a usable workaround for this .NET shortcoming. :thumbsup:

Comment: Thanks also to Eddy, which I've marked as the Answer. Getting lazy with code-completion led me to not see the .MainWindowHandle member of process, which is the HWND I need. Also, interesting to note that for a form, the "this" pointer has a Handle member which is the form's HWND.

Posted 3-Feb-10 11:25am

sloughin

Updated 4-Feb-10 4:05am

v3

Add a Solution

2 solutions

Solution 1

It's not identical, because that makes zero sense. A process has a handle, and it can have many windows associated with it. It's a different thing entirely.

This[^] seems to have a solution, found it with google.

Posted 3-Feb-10 11:42am

Christian Graus

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Eddy Vluggen · Accepted Answer · 2010-02-03T13:54:00

sloughin wrote:
I don't understand why p.Handle isn't identical to an old fashioned HWND, and even if it isn't, why there isn't an easy conversion between the two types somewhere in InteropServices.

They represent different things - a proces and a Window. A proces like a console has a handle, but no forms. There's a WaitForInputIdle in the code below to give the proces the time to load and build it's mainform.

C#

p =Process.Start("Calc.exe"); 
p.WaitForInputIdle(); 
hMainWindow = p.MainWindowHandle;
SetParent(hMainWindow, this.Handle);

Enjoy :)