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Summary
The breadth and power of the .NET Framework combined with the RAD features of a language such as Visual Basic .NET raise the ceiling for developers, while at the same time making it simpler to create robust applications such as Windows services.
Listing 1 contains both the ServiceBase and Installer classes discussed in the article.
Listing 1—A Windows Service Template.
Option Strict On
Imports System.ServiceProcess
Imports System.Configuration
Imports System.Timers
Imports System.ComponentModel
Imports System.Configuration.Install
Public Class MyService : Inherits System.ServiceProcess.ServiceBase
Public Sub New()
MyBase.New()
InitializeComponent()
'Called only when first loaded not with each start and stop
' Set the properties for the service
With Me
.ServiceName = "MyService"
.CanShutdown = True
.CanStop = True
.CanPauseAndContinue = False
.AutoLog = True
End With
End Sub
'UserService overrides dispose to clean up the component list.
Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
If disposing Then
If Not (components Is Nothing) Then
components.Dispose()
End If
End If
MyBase.Dispose(disposing)
End Sub
' The main entry point for the process
<MTAThread()> _
Shared Sub Main()
Dim ServicesToRun() As System.ServiceProcess.ServiceBase
ServicesToRun = New System.ServiceProcess.ServiceBase() {New MyService()}
System.ServiceProcess.ServiceBase.Run(ServicesToRun)
End Sub
'Required by the Component Designer
Private components As System.ComponentModel.IContainer
<System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
components = New System.ComponentModel.Container()
Me.ServiceName = "My Service"
End Sub
Private _process As Timer
Private _interval As Long
Protected Overrides Sub OnStart(ByVal args() As String)
' Get the registry values
_getRegValues()
' Configure and turn on the timer
_process = New Timer(_interval)
AddHandler _process.Elapsed, AddressOf OnTimer
_process.Start()
End Sub
Private Sub OnTimer(ByVal sender As Object, ByVal e As ElapsedEventArgs)
' Timer has gone off
Me.EventLog.WriteEntry("Waking Up", EventLogEntryType.Information)
_process.Stop()
_processWork()
_process.Start()
End Sub
Private Sub _processWork()
' Do the work
' Update the perf counters
Try
Dim counter As PerformanceCounter
counter = New PerformanceCounter("My Counter", "SomeValue", False)
counter.IncrementBy(1)
counter.Dispose()
Catch e As Exception
' Don't care about the exception if any
Me.EventLog.WriteEntry(e.Message, EventLogEntryType.Error)
End Try
End Sub
Protected Overrides Sub OnStop()
' Clean up the timer
_process.Stop()
RemoveHandler _process.Elapsed, AddressOf OnTimer
_process.Dispose()
End Sub
Private Function _getRegValues() As Boolean
' get values from the registry if needed
End Function
End Class
<RunInstaller(True)> _
Public Class MyServiceInstall : Inherits Installer
' For each service
Private WithEvents _serviceInstaller As ServiceInstaller
' For the entire executable
Private _processInstaller As ServiceProcessInstaller
Private _perfCounterInstaller As PerformanceCounterInstaller
Public Sub New()
MyBase.New()
' Instantiate installers for process and services.
_processInstaller = New ServiceProcessInstaller()
_serviceInstaller = New ServiceInstaller()
_perfCounterInstaller = New PerformanceCounterInstaller()
' The services will run under the system account.
_processInstaller.Account = ServiceAccount.LocalSystem
' The services will be started manually.
_serviceInstaller.StartType = ServiceStartMode.Manual
' ServiceName must equal those on ServiceBase derived classes.
_serviceInstaller.ServiceName = "MyService"
_serviceInstaller.DisplayName = "My Service"
' Set up the perf counters
Dim counter1 As New CounterCreationData("My Counter", _
"The description goes here.", _
PerformanceCounterType.NumberOfItems32)
_perfCounterInstaller.CategoryName = "My Service"
_perfCounterInstaller.Counters.Add(counter1)
_perfCounterInstaller.Counters.Add(counter)
' Add installers to collection. Order is not important.
' here is where you add performance monitor installers or event log installers
Installers.Add(_serviceInstaller)
Installers.Add(_processInstaller)
Installers.Add(_perfCounterInstaller)
End Sub
' Catch the events
Public Sub sAfterInstall(ByVal sender As Object, _
ByVal e As System.Configuration.Install.InstallEventArgs) _
Handles serviceInstaller.AfterInstall
' Log a successful install
End Sub
Public Sub sAfterUninstall(ByVal sender As Object, _
ByVal e As System.Configuration.Install.InstallEventArgs) _
Handles serviceInstaller.AfterUninstall
' Log a successful uninstall
End Sub
Public Overrides Sub Install(ByVal state As IDictionary)
MyBase.Install(state)
' Write default values to the registry
End Sub
Public Overrides Sub UnInstall(ByVal state As IDictionary)
' Delete registry values
End Sub
End Class
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