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Editorial Team
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Asked: 2026-05-18T04:21:02+00:00

This is a somewhat unusual problem. I’m presently working on an effort to automate

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This is a somewhat unusual problem. I’m presently working on an effort to automate an Office application. Basically the issue is that my app is able to interact with the Office app correctly when I execute my app via RDP, but I am unable to send keystrokes using SendInput() if I set up the application to spawn from a windows service. OS is Win03 Std.

When spawning the app from a windows service I’m able to read window captions, automate through the interop, etc. as expected via pinvoke, but the SendInput() messages seemingly vanish even though the call returns a 1. All I’m trying to do at this point is send an escape keystroke to a dialog.

I’ve tried sending the keystrokes both as virtual keys and scancodes.

Any ideas or tips? Thanks in advance!

(BTW: I do realize that this sort of automation isn’t supported/sanctioned by MSFT.)

EDIT:
Just in case anyone else has this issue, this works:

[DllImport("user32")]

public static extern bool PostMessage(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam);


bool returnVal = NativeWin32.PostMessage(popup, 0x0100, new IntPtr(0x1b), IntPtr.Zero);
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1 Answer

  1. Editorial Team

    I believe that SendInput will send keys to current active window (or window that has focus). Typically, windows services would be associated with different desktop (that interactive desktop) – so App launched from windows service would also be associated with the background desktop – so no active window (or window with focus) and that’s may be the reason sendinout not working. You can perhaps try simulating key click by using SendMessage or PostMessage – you will need window handle for that.

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