windows service with keybd_event is not printing the value in active window

Hello,

I have created a windows service in c#. I would like to use windows service and print the "x" value in the active window wherever the cursor located. I have used Keybd_event to print the value. Unfortunately i am unable to see the value in the active window. I assume Keybd_event is not fired. I have added log messages before and after keybd_event event, log messages are creating perfectly. However if i use the same code to print the value from an windows application i am able to print the value. I am attaching my code whatever i have used to print the value

Here is the code i have used in windows service and application

using System;
using System.Collections.Generic;
using System.Text;

namespace SmartcardLibrary
{
/*
* ---------------------------------------------------------------------------------------
* Class Name : PrintToScreen
* Purpose : Normal class inherits the keyboardevents abstract class and used to
* get the correct keyborad character and print it on active window
* ---------------------------------------------------------------------------------------
* Orig Author : JAGANMOHAN NAIDU PENIKALAPATI
* Created Date : March 24 2008
* ---------------------------------------------------------------------------------------
* Updated Author :
* Updated Date :
* ---------------------------------------------------------------------------------------
* */

public class PrintToScreen : KeyboardEvents
{
private static log4net.ILog logError = log4net.LogManager.GetLogger("SmartCardErrorLogger");
private const string NEW_LINE = "\n";

private const uint KEYEVENTFKEYUP = 0x2;
private const byte VKCAPSLOCK = 0x14;
private const byte SCCAPSLOCK = 0xBA;
private const byte VKTAB = 0x09;
private const byte SCTAB = 0x8F;

public static void Print(string input)
{
try
{
//logError.Error("PRINT SCREEN TAG ID: " + input + NEW_LINE);
input = input.ToUpper();
byte[] virtualKey = Encoding.UTF8.GetBytes(input);
byte[] bScanCode = new byte[input.Length];
for (int count = 0; count < virtualKey.Length; count++)
{
bScanCode[count] = ScanCode(virtualKey[count]);
}
for (int i = 0; i < virtualKey.Length; i++)
{
if (GetKeyState(VKCAPSLOCK) == 0)
keybd_event(VKCAPSLOCK, SCCAPSLOCK, 0, 0); //Caps Lock Press Event
keybd_event(virtualKey[i], bScanCode[i], 0, 0); //Key press event
//UnsafeNativeMethods.keybd_event(virtualKey[i], bScanCode[i], KEYEVENTF_KEYUP, 0); //Key release event
//UnsafeNativeMethods.keybd_event(VKCAPSLOCK, SCCAPSLOCK, KEYEVENTFKEYUP, 0); //Caps Lock release Event
}
keybd_event(VKTAB, SCTAB, 0, 0); //Tab press event
//logError.Error(input + NEW_LINE + NEW_LINE);
}
catch (Exception ex)
{
logError.Error(ex.Message + NEW_LINE + ex.StackTrace);
}
}

private static byte ScanCode(byte Character)
{
byte result = Convert.ToByte(MapVirtualKey(Character, 0x1)); //0x1 indicates VirtualCode to Scan code conversion
return result;
}

}///
}///

This code is working for application but not working for windows service...

your suggestions on this issue would be appreciated

1 Reply

Know the answer? Post it — somebody with the same question will find it here.

Yaswanth Chowdary18y ago
I got the answer for my question.

For any windows service which is developed using local system account must be checked an option "Allow service to interact with desktop" in the service properties.