I needed a simple Windows Service to request a web page at set intervals indefinitely. Windows Services are the best way of doing this as they have the ability to start automatically when the computer boots up and can be paused, stopped and restarted. You can also get them to write events to the Windows Event log.
I found this Windows Service sample tutorial on The Code Project and downloaded the code to familiarise myself with the basics. The tutorial lacked a timer and the code to request a URL though so I had to add this functionality.
Visual Studio Standard edition doesn't have a Windows Service template, but you can still create a Windows Service, you just need to do a bit of extra work.
After some research and a bit of coding I added two new methods:
private void ServiceTimer_Tick(object sender, ElapsedEventArgs e)
{
this.timer.Stop();
DoWork();
this.timer.Start();
}
void DoWork()
{
WebClient client = new WebClient();
client.Headers.Add("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.0.3705;)");
Stream data = client.OpenRead(URL to request here);
client.Dispose();
data.Dispose();
}
I overrode the OnStart() method of ServiceBase to enable the timer and start it. I also overrode the OnStop() method to disable the timer.
The DoWork() method simply creates an instance of WebClient and reads in the URL you want to request.
Then in the constructor I set the timer interval and added an event handler to raise the ServiceTimer event when the interval elapses. The event handler simply stops the timer, calls the DoWork() method and then restarts the timer.
public static void Main()
{
ServiceBase.Run(new Service3());
}
public Service3()
{
InitializeComponent();
// Duration 1 hour
double interval = 3600000;
timer = new Timer(interval);
timer.Elapsed += new ElapsedEventHandler(this.ServiceTimer_Tick);
}
To install the Service you need to publish the project in Visual Studio. Then use InstallUtil.exe following the process below:
- Open a Visual Studio .NET Command Prompt
- Change to the bin\Debug directory of your project location (bin\Release if you compiled in release mode)
- Issue the command InstallUtil.exe MyWindowsService.exe to register the service and have it create the appropriate registry entries
- Open the Computer Management console by right clicking on My Computer on the desktop and selecting Manage
- In the Services section underneath Services and Applications you should now see your Windows Service included in the list of services
- Start your service by right clicking on it and selecting Start
Each time you need to change your Windows Service it will require you to uninstall and reinstall the service. Prior to uninstalling the service make sure you close the Services management console. To uninstall the service simply reissue the same InstallUtil command used to register the service and add the /u command switch.
e.g. InstallUtil.exe /u MyWindowsService.exe
When you install the service on a server you can find the InstallUtil.exe in the .NET framework folder e.g. C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727
