.net - Why won't my solution work to P/Invoke NotifyServiceStatusChange in C#?

Question

I am trying to P/Invoke the NotifyServiceStatusChange event in C# to check when a service has stopped. I managed to get it to compile and run without any errors, but now, when I stop the service, it doesn't seem to want to notify that its dead. Any ideas why that could be? You can test it out by copying this code into a blank console application; just be sure to replace "My Service Name" with your service name (there are two instances of this string below).

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    class Program
    {

        public delegate void StatusChanged(IntPtr parameter);

        public class SERVICE_NOTIFY : MarshalByRefObject
        {
            public uint dwVersion;
            public StatusChanged pfnNotifyCallback;
            public IntPtr pContext;
            public uint dwNotificationStatus;
            public SERVICE_STATUS_PROCESS ServiceStatus;
            public uint dwNotificationTriggered;
            public IntPtr pszServiceNames;
        };

        public struct SERVICE_STATUS_PROCESS {
            public uint dwServiceType;
            public uint dwCurrentState;
            public uint dwControlsAccepted;
            public uint dwWin32ExitCode;
            public uint dwServiceSpecificExitCode;
            public uint dwCheckPoint;
            public uint dwWaitHint;
            public uint dwProcessId;
            public uint dwServiceFlags;
        };

        [DllImport("advapi32.dll", SetLastError = true, CharSet = CharSet.Auto)]
        static extern IntPtr OpenService(IntPtr hSCManager, string lpServiceName, uint dwDesiredAccess);

        [DllImport("advapi32.dll", EntryPoint = "OpenSCManagerW", ExactSpelling = true, CharSet = CharSet.Unicode, SetLastError = true)]
        public static extern IntPtr OpenSCManager(string machineName, string databaseName, uint dwAccess);

        [DllImport("advapi32.dll", SetLastError = true)]
        public static extern uint NotifyServiceStatusChange(IntPtr hService, uint dwNotifyMask, ref IntPtr pNotifyBuffer);

        public static SERVICE_NOTIFY notify;
        public static GCHandle notifyHandle;
        public static IntPtr unmanagedNotifyStructure;

        static void Main(string[] args)
        {
            IntPtr hSCM = OpenSCManager(null, null, (uint)0xF003F);
            if (hSCM != IntPtr.Zero)
            {
                IntPtr hService = OpenService(hSCM, "My Service Name", (uint)0xF003F);
                if (hService != IntPtr.Zero)
                {
                    StatusChanged changeDelegate = ReceivedStatusChangedEvent;
                    notify = new SERVICE_NOTIFY();
                    notify.dwVersion = 2;
                    notify.pfnNotifyCallback = changeDelegate;
                    notify.pContext = IntPtr.Zero;
                    notify.dwNotificationStatus = 0;
                    SERVICE_STATUS_PROCESS process;
                    process.dwServiceType = 0;
                    process.dwCurrentState = 0;
                    process.dwControlsAccepted = 0;
                    process.dwWin32ExitCode = 0;
                    process.dwServiceSpecificExitCode = 0;
                    process.dwCheckPoint = 0;
                    process.dwWaitHint = 0;
                    process.dwProcessId = 0;
                    process.dwServiceFlags = 0;
                    notify.ServiceStatus = process;
                    notify.dwNotificationTriggered = 0;
                    notify.pszServiceNames = Marshal.StringToHGlobalUni("My Service Name");
                    notifyHandle = GCHandle.Alloc(notify);
                    unmanagedNotifyStructure = Marshal.AllocHGlobal((IntPtr)(notifyHandle));
                    NotifyServiceStatusChange(hService, (uint)0x00000001, ref unmanagedNotifyStructure);
                    Console.WriteLine("Waiting for the service to stop. Press enter to exit.");
                    Console.ReadLine();
                }
            }
        }

        public static void ReceivedStatusChangedEvent(IntPtr parameter)
        {
            Console.WriteLine("Service stopped.");
        }
    }
}

Answer 1

If you want to keep the functionality you are attempting at present, you will need to multithread.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;
using System.Threading.Tasks;


namespace ConsoleApplication1
{
    class Program
    {
        [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
        public class SERVICE_NOTIFY 
        {
            public uint dwVersion;
            public IntPtr pfnNotifyCallback;
            public IntPtr pContext;
            public uint dwNotificationStatus;
            public SERVICE_STATUS_PROCESS ServiceStatus;
            public uint dwNotificationTriggered;
            public IntPtr pszServiceNames;
        };

        [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
        public struct SERVICE_STATUS_PROCESS
        {
            public uint dwServiceType;
            public uint dwCurrentState;
            public uint dwControlsAccepted;
            public uint dwWin32ExitCode;
            public uint dwServiceSpecificExitCode;
            public uint dwCheckPoint;
            public uint dwWaitHint;
            public uint dwProcessId;
            public uint dwServiceFlags;
        };

        [DllImport("advapi32.dll", SetLastError = true, CharSet = CharSet.Auto)]
        static extern IntPtr OpenService(IntPtr hSCManager, string lpServiceName, uint dwDesiredAccess);

        [DllImport("advapi32.dll", EntryPoint = "OpenSCManagerW", ExactSpelling = true, CharSet = CharSet.Unicode, SetLastError = true)]
        public static extern IntPtr OpenSCManager(string machineName, string databaseName, uint dwAccess);

        [DllImport("advapi32.dll", SetLastError = true)]
        public static extern uint NotifyServiceStatusChange(IntPtr hService, uint dwNotifyMask, IntPtr pNotifyBuffer);

        [DllImportAttribute("kernel32.dll", EntryPoint = "SleepEx")]
        public static extern uint SleepEx(uint dwMilliseconds, [MarshalAsAttribute(UnmanagedType.Bool)] bool bAlertable);

        public static SERVICE_NOTIFY notify;
        public static GCHandle notifyHandle;
        public static IntPtr unmanagedNotifyStructure;

        static void Main(string[] args)
        {
            IntPtr hSCM = OpenSCManager(null, null, (uint)0xF003F);
            if (hSCM != IntPtr.Zero)
            {
                IntPtr hService = OpenService(hSCM, "Apache2.2", (uint)0xF003F);
                if (hService != IntPtr.Zero)
                { 
                    StatusChanged changeDelegate = ReceivedStatusChangedEvent;


                    notify = new SERVICE_NOTIFY();
                    notify.dwVersion = 2;
                    notify.pfnNotifyCallback = Marshal.GetFunctionPointerForDelegate(changeDelegate);
                    notify.pContext = IntPtr.Zero;
                    notify.dwNotificationStatus = 0;
                    SERVICE_STATUS_PROCESS process;
                    process.dwServiceType = 0;
                    process.dwCurrentState = 0;
                    process.dwControlsAccepted = 0;
                    process.dwWin32ExitCode = 0;
                    process.dwServiceSpecificExitCode = 0;
                    process.dwCheckPoint = 0;
                    process.dwWaitHint = 0;
                    process.dwProcessId = 0;
                    process.dwServiceFlags = 0;
                    notify.ServiceStatus = process;
                    notify.dwNotificationTriggered = 0;
                    notify.pszServiceNames = Marshal.StringToHGlobalUni("Apache2.2");
                    notifyHandle = GCHandle.Alloc(notify, GCHandleType.Pinned);
                    unmanagedNotifyStructure = notifyHandle.AddrOfPinnedObject();
                    NotifyServiceStatusChange(hService, (uint)0x00000001, unmanagedNotifyStructure);

                    GC.KeepAlive(changeDelegate);

                    Console.WriteLine("Waiting for the service to stop. Press enter to exit.");
                    while (true)
                    {
                        try
                        {
                            string keyIn = Reader.ReadLine(500);
                            break;
                        }
                        catch (TimeoutException)
                        {
                            SleepEx(100,true);
                        }
                    }
                    notifyHandle.Free();
                }
            }
        }
        [UnmanagedFunctionPointer(CallingConvention.StdCall)]
        public delegate void StatusChanged(IntPtr parameter);
        public static void ReceivedStatusChangedEvent(IntPtr parameter)
        {
            Console.WriteLine("Service stopped.");
        }

    }
}

class Reader
{
    private static Thread inputThread;
    private static AutoResetEvent getInput, gotInput;
    private static string input;

    static Reader()
    {
        inputThread = new Thread(reader);
        inputThread.IsBackground = true;
        inputThread.Start();
        getInput = new AutoResetEvent(false);
        gotInput = new AutoResetEvent(false);
    }

    private static void reader()
    {
        while (true)
        {
            getInput.WaitOne();
            input = Console.ReadLine();
            gotInput.Set();
        }
    }

    public static string ReadLine(int timeOutMillisecs)
    {
        getInput.Set();
        bool success = gotInput.WaitOne(timeOutMillisecs);
        if (success)
            return input;
        else
            throw new TimeoutException("User did not provide input within the timelimit.");
    }
}