>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");
>        }

Wrong scope. You have a variable type in front of the variable when you instantiate it. This causes it to create a local variable in the method instead of using the field in your class.