C# - Command window appears a tenth of a second before disappear

Question

I'm trying to hide command window when process starts. I launch McAfee virus scan using this ProcessStartInfo config:

ProcessStartInfo procInfo = new ProcessStartInfo();
procInfo.FileName = args[0];
...
procInfo.RedirectStandardOutput = true;
procInfo.WindowStyle = ProcessWindowStyle.Hidden;
procInfo.CreateNoWindow = false;
procInfo.UseShellExecute = false;
process.StartInfo = procInfo;

Then, I try:

process.Start();
process.CloseMainWindow();

And also:

process.Start();
while (process.MainWindowHandle == IntPtr.Zero)
{
   process.Refresh();
}
var handle = process.MainWindowHandle;
ShowWindow(handle, 0) //ShowWindow from user32.dll

But in both cases command window appears and before it is displayed completely, it desappears (just like maximize window and immediately minimize it). I have also played with all possible ProcessStartInfo properties combinations. I need no window is displayed in any moment. How could I achieve that? Thanks in advance!

@techspider, this is part of bigger process, I cannot schedule it :( — AdSsa, Apr 27 '16 at 15:00
@BugFinder, behavior is the same with CreateNoWindow set to false or true. — AdSsa, Apr 27 '16 at 15:00
if you start it minimized do you only then breifly see an icon in the taskbar? Im guessing its coded to always show its just making the best of a bad job. — BugFinder, Apr 27 '16 at 15:06

score 0 · Accepted Answer · edited May 23 '17 at 11:44

For the Code Blocks as shown in your question, the behavior is normal.

Let's have a look at them...

//[...]
procInfo.CreateNoWindow = false; //That's not what you meant
procInfo.UseShellExecute = false;
process.Start(); //Will show up the console window
process.CloseMainWindow(); //Will close the main window (probably also the whole application)

Between process.Start(); and process.CloseMainWindow(); is a short time frame, where the application is visible.

Like described by @BugFinder, it should be enough to edit the CreateNoWindow Value from false to true.
Check if that works.

Your second try is getting you further away:

process.Start();
while (process.MainWindowHandle == IntPtr.Zero)
{
   process.Refresh(); //Let's do this as long as there is no window...
}
var handle = process.MainWindowHandle; //This occurs, when there is *already* a window.
ShowWindow(handle, 0) //ShowWindow from user32.dll

The idea of using Shell Functions is basically not bad, but this code is doing the same like the code above (and is also unmanaged).

Let's try a different way and take the C# Sample from PInvoke.Net: (not more managed than ShowWindow()...)

public static void StartupNotepad()
{
     const uint NORMAL_PRIORITY_CLASS = 0x0020;
     const uint STARTF_USESHOWWINDOW = 0x1;     //IMPORTANT for you
     bool retValue;
     string Application = Environment.GetEnvironmentVariable("windir") + @"\Notepad.exe";
     string CommandLine = @" c:\boot.ini";  //Funny
     PROCESS_INFORMATION pInfo = new PROCESS_INFORMATION();
     STARTUPINFO sInfo = new STARTUPINFO();
     sInfo.wShowWindow = 0;                     //IMPORTANT for you - See http://pinvoke.net/default.aspx/Enums/ShowWindowCommand.html
     sInfo.dwFlags = STARTF_USESHOWWINDOW;      //IMPORTANT for you
     SECURITY_ATTRIBUTES pSec = new SECURITY_ATTRIBUTES();
     SECURITY_ATTRIBUTES tSec = new SECURITY_ATTRIBUTES();
     pSec.nLength = Marshal.SizeOf(pSec);
     tSec.nLength = Marshal.SizeOf(tSec);
     retValue = CreateProcess(Application,CommandLine,
     ref pSec,ref tSec,false,NORMAL_PRIORITY_CLASS,
     IntPtr.Zero,null,ref sInfo,out pInfo);

     Console.WriteLine("Process ID (PID): " + pInfo.dwProcessId);
     Console.WriteLine("Process Handle : " + pInfo.hProcess);
}

This example demonstrates the use of CreateProcess (MSDN Link at the bottom) in a very static manner.
I suggest you to write a more dynamic function and play around with it. The PROCESS_INFORMATION structure allows you to manipulate the newly created process later in your application. If your problem still persists using the CreateProcess() Call, it's to check whether the started application does some tricky stuff on itself. And last but not least whether the problem occurs not only on your computer...

Here are some more references:

EDIT:

Probably a workaround, but if your 3rd party App is designed to show a Window and tries to ignore your requests, STARTUPINFO also has dwX and dwY, which sets the Window's position if dwFlags specifies STARTF_USEPOSITION. Same for dwXSize and dwYSize.

If all else fails, you could give it a try and pass positions and sizes, which make the proces appear invisible. Cheers.

It has been more complicated to launch McAfee Scan than notepad in order to catch and redirect outputs, close processes or catch windows handlers. Thanks for the clue about `CreateProcess()`. :) — AdSsa, May 11 '16 at 11:51
`in order to catch and redirect outputs` This is what [`PROCESS_INFORMATION`](https://msdn.microsoft.com/en-us/library/windows/desktop/ms684873%28v=vs.85%29.aspx) is referenced for. — Clijsters, May 18 '16 at 14:20

C# - Command window appears a tenth of a second before disappear

1 Answers1