Hi,

I'm writing my first ever Windows service in C# and am getting this error when I stop the service (using the services applet).

Failed to stop service. System.NullReferenceException: Object reference not set to an instance of an object.
at ResRepricerImportFolderMonitor.ResRepricerImportFolderMonitor.OnStop() in D:\Development\VS2010\ResPricer\ResRepricerImportFolderMonitor\ResRepricerImportFolderMonitor.cs:line 106
at System.ServiceProcess.ServiceBase.DeferredStop()

The error occurs on this line:

watcher.EnableRaisingEvents = false;

in the OnStop method.

Is my watcher being automatically shutdown or do I have it in the wrong scope?

namespace ResRepricerImportFolderMonitor
{
    public partial class ResRepricerImportFolderMonitor : ServiceBase
    {
        public enum ServiceState
        {
            SERVICE_STOPPED = 0x00000001,
            SERVICE_START_PENDING = 0x00000002,
            SERVICE_STOP_PENDING = 0x00000003,
            SERVICE_RUNNING = 0x00000004,
            SERVICE_CONTINUE_PENDING = 0x00000005,
            SERVICE_PAUSE_PENDING = 0x00000006,
            SERVICE_PAUSED = 0x00000007,
        }

        [StructLayout(LayoutKind.Sequential)]
        public struct ServiceStatus
        {
            public long dwServiceType;
            public ServiceState dwCurrentState;
            public long dwControlsAccepted;
            public long dwWin32ExitCode;
            public long dwServiceSpecificExitCode;
            public long dwCheckPoint;
            public long dwWaitHint;
        };

        [DllImport("advapi32.dll", SetLastError = true)]
        private static extern bool SetServiceStatus(IntPtr handle, ref ServiceStatus serviceStatus);

        private FileSystemWatcher watcher = null;

        public ResRepricerImportFolderMonitor()
        {
            InitializeComponent();
        }

        protected override void OnStart(string[] args)
        {
            // Update the service state to Start Pending.
            ServiceStatus serviceStatus = new ServiceStatus();
            serviceStatus.dwCurrentState = ServiceState.SERVICE_START_PENDING;
            serviceStatus.dwWaitHint = 100000;
            SetServiceStatus(this.ServiceHandle, ref serviceStatus);

            // Create a new FileSystemWatcher with the path
            //and text file filter

            string CSVFolder = ConfigurationManager.AppSettings["CSVFolder"];
            string CSVFolderProcessed = ConfigurationManager.AppSettings["CSVFolderProcessed"];

            FileSystemWatcher watcher = new FileSystemWatcher(CSVFolder, "*.csv");

            //Watch for changes in LastAccess and LastWrite times, and
            //the renaming of files or directories.
            watcher.NotifyFilter = NotifyFilters.LastAccess
                                 | NotifyFilters.LastWrite
                                 | NotifyFilters.FileName
                                 | NotifyFilters.DirectoryName;

            // Add event handlers.
            //watcher.Changed += new FileSystemEventHandler(OnChanged);
            watcher.Created += new FileSystemEventHandler(OnChanged);
            //watcher.Deleted += new FileSystemEventHandler(OnChanged);
            //watcher.Renamed += new RenamedEventHandler(OnRenamed);

            // Begin watching.
            watcher.EnableRaisingEvents = true;

            // Update the service state to Running.
            serviceStatus.dwCurrentState = ServiceState.SERVICE_RUNNING;
            SetServiceStatus(this.ServiceHandle, ref serviceStatus);

            LogEvent("started");
       }

        protected override void OnStop()
        {
            watcher.EnableRaisingEvents = false; // error occurs here
            watcher.Dispose();

            LogEvent("stopped");
        }