How to catch SERVICE_CONTROL_SHUTDOWN code in Windows Service Program

I’m working on programming a Windows service program recently.

The problem I faced with while programming is that Windows OS doesn’t turn off normally when I install my program on it. It takes too long time to turn off the system. It seems my program is the cause for the problem.

I tried to find a solution on the internet, and I found adding ‘SERVICE_CONTROL_SHUTDOWN’ to my code can be the solution. I did so, but my program doesn’t catch ‘SERVICE_CONTROL_SHUTDOWN’ and I don’t know why…

Does anyone know why it is so… and can anyone tell me how to fix it? Thanks.

I put a snippet from my code below.

// method that sets service status. 
void SvcSetStatus(DWORD dwState, DWORD dwAccept = SERVICE_ACCEPT_STOP | SERVICE_ACCEPT_SHUTDOWN )
        {
            SERVICE_STATUS ss;
            ss.dwServiceType = SERVICE_WIN32_OWN_PROCESS;
            ss.dwCurrentState = dwState;
            ss.dwControlsAccepted = dwAccept;
            ss.dwWin32ExitCode = 0;
            ss.dwServiceSpecificExitCode = 0;
            ss.dwCheckPoint = 0;
            ss.dwWaitHint = 0;


            g_NowState = dwState; 
            SetServiceStatus(g_hSrv, &ss);

        }

// method of service handler 
void SvcHandler(DWORD fdwControl)
        {

            if (fdwControl == g_NowState)
            {
                return;

            }

            switch (fdwControl)
            {
                case SERVICE_CONTROL_PAUSE:

                    break;
                case SERVICE_CONTROL_CONTINUE:

                    break;
                case SERVICE_CONTROL_STOP:
                    ShutdownService(FALSE);
                    break;
                case SERVICE_CONTROL_INTERROGATE:
                    break;
                case SERVICE_CONTROL_PRESHUTDOWN:

                    ShutdownService(TRUE); //???
                    break;
                case SERVICE_CONTROL_SHUTDOWN:

                    ShutdownService(TRUE); //service finalize function (parameter is for shutdown or not)

                    break;
                default:
                    SvcSetStatus(g_NowState);
                    break;

            }
        }