Question

I am trying to create a simple service in C# using VS2008 that creates a text file when the computer goes into sleep mode. My current code throws out the following error:

‘SleepNotifierService.WqlEventQuery’ does not contain a constructor that takes ‘1’ arguments

Now I looked in the Object browser, and it looks like it does take in one argument. This is what the browser had to say:

public WqlEventQuery(string queryOrEventClassName)

Here is my code:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Linq;
using System.ServiceProcess;
using System.Text;
using System.Management;
using System.IO;

namespace SleepNotifierService
{
    public class WqlEventQuery : EventQuery { }

    public partial class Service1 : ServiceBase
    {
        ManagementEventWatcher _watcher;

        public Service1()
        {
            InitializeComponent();
        }

        protected override void OnStart(string[] args)
        {
            WqlEventQuery query = new WqlEventQuery("Win32_PowerManagementEvent");
            _watcher = new ManagementEventWatcher(query);
            _watcher.EventArrived += new EventArrivedEventHandler(watcher_EventArrived);
            _watcher.Start();
        }

        protected override void OnStop()
        {
            _watcher.Stop();
        }

        void watcher_EventArrived(object sender, EventArrivedEventArgs e)
        {
            try
            {
                int eventType = Convert.ToInt32(e.NewEvent.Properties["EventType"].Value);
                switch (eventType)
                {
                    case 4:
                        Sleep();
                        break;
                    case 7:
                        Resume();
                        break;
                }
            }
            catch (Exception ex)
            {
                //Log(ex.Message);
            }
        }

        public void Sleep()
        {
            StreamWriter SW;
            SW = File.CreateText("c:\\MyTextFile.txt");
            SW.WriteLine("Sleep mode initiated");
            SW.Close();
        }

        public void Resume()
        {
        }

    }
}

Am I interpreting that object browser wrong? I’m new to creating services and C#/.NET in general so it might be something trivial.

Appreciate any help,

Tomek

Answer 1

You’re using wrong WqlEventQuery. There’s one defined in System.Management and it indeed has a one-argument constructor, but there’s also your custom WqlEventQuery class.

If you want to use .NET BCL’s class, you’ll have to fully qualify it:

var query = new System.Management.WqlEventQuery("Win32_PowerManagementEvent");

or even prefix it with global keyword:

var query = new global::System.Management.WqlEventQuery("Win32_PowerManagementEvent");