Create an Unattended Windows Service using .NET

A Windows Service is a process that runs unattended and doesn't have a user interface. Windows Services can run on WinNT, Win2K, Windows Server 2003, and WinXP. Services can start when the operating system boots and other applications can interact with them.

Services can perform functions such as logging, auditing, database connection pooling, etc. This sample creates a service that logs events to a file. Events originate in a sample application that simulates when gates in a security fence open or close. The .NET solution contains two projects: the WindowsService project which implements the service and the driver project that utilizes it.

You can walk through the code which is straightforward. Here, I'll mention a few important details.

To create a Windows Service project, select the Windows Service template in the VS.NET IDE. I named the project AppMonitor. Open AppMonitor.VB in Designer view and look at its properties. You can set properties telling Windows that the service will handle shutdown, pause, continue, and other events. The AutoLog property tells the service to automatically write to the Event Log when the it starts and stops.

Viewing the code, you see the AppMonitor class inherits from the System.ServiceProcess.ServiceBase namespace. Also there is an handler for the various service events (OnStart, OnStop, OnPause...). These handlers override those in the System.ServiceProcess.ServiceBase class and allow the service to execute the desired logic when it starts, stops, etc. The OnStart procedure takes a string array parameter. You pass values into OnStart using the Services MMC snap-in in Control Panel.

The OnCustomCommand event allows an application to interact with a running service by passing in integer values. Code in OnCustomCommand must interogate the value and execute the corresponding logic. Integer values must be in the range 128 to 255. Interaction with a service is primitive and one way, OnCustomCommand cannot return a value. Also, your service has hard coded ties to the application(s) that use it.

The driver application let's you start and stop the service. If has a reference to the System.ServiceProcess.dll and creates an instance of a ServiceController which is used to control a service. To start or stop a service you call the ServiceController's start or stop method then wait for the service's status to change using the controller's WaitForStatus method. Once the service has started you send integer commands to it using the ServiceController's ExecuteCommand method.

Before you can run the code you must compile it and install the service. Build the .NET solution then open the AppMonitor.VB in Designer view. Go to properties and click the Add Installer link. This adds a ProjectInstaller.VB class which updates the Windows Registry with your service. To install the service you must run the InstallUtil component described below.

Download Source Code

Instructions

Download the source code and compile it. Open a Visual Studio .NET 2003 Command Prompt and navigate to \bin folder containing the compiled .EXE. Install the service by typing InstallUtil AppMonitor.Exe into the command prompt and hitting Enter (you may need to specify the complete path to InstallUtil which is in the .NET Framework folder). Look at the log files create in the \bin folder. Run the driver sample and step through the code. Examine the monitor.txt log file created in the root folder.

Notes

This code will not run under version 1.0 of the .Net framework. You must use the InstallUtil program from V1.1 of the Framework. To uninstall the service, use the InstallUtil /u AppMonitor.exe command.








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