(NET) NET (2021)

Windows service example

I was written a lot of various WinServices, but still have no page with description how to do this type of application. In this page I wan to discuss about WinService. So we can start from WinService template:



and type this common service template:


   1:  Imports System.Threading
   2:  Imports System.Timers
   3:  Imports Timer = System.Timers.Timer
   4:  Imports System.IO
   5:  Imports System.Text
   6:   
   7:  Public Class PromocodeCacheCreater
   8:      Private Timer As Timer
   9:      Protected Overrides Async Sub OnStart(ByVal args() As String)
  10:          Try
  11:  ReStart:
  12:              Timer = New Timer(CInt(My.Settings.UpdateIntervalMinutes) * 60 * 1000) 'milliseconds
  13:              AddHandler Timer.Elapsed, AddressOf TimerElapsed
  14:              Timer.Start()
  15:              Await BuildCache()
  16:          Catch ex As Exception
  17:              EventLog.WriteEntry("PromocodeCacheCreater", "Exception in OnStart " & IIf(String.IsNullOrWhiteSpace(ex.Message), "Empty", ex.Message) & Environment.NewLine & ex.StackTrace)
  18:              My.Computer.FileSystem.WriteAllText(My.Settings.OutPathRoot & "Index.htm", "Exception in OnStart " & IIf(String.IsNullOrWhiteSpace(ex.Message), "Empty", ex.Message) & Environment.NewLine & ex.StackTrace, False)
  19:              WriteLog($"Exception in OnStart & {IIf(String.IsNullOrWhiteSpace(ex.Message), "Empty", ex.Message) & Environment.NewLine & ex.StackTrace} {vbCrLf}")
  20:              GoTo ReStart
  21:          End Try
  22:      End Sub
  23:      Private Async Sub TimerElapsed(Sender As Object, E As ElapsedEventArgs)
  24:          Await BuildCache()
  25:      End Sub
  26:   
  27:      Protected Overrides Async Sub OnStop()
  28:          Try
  29:              If Timer IsNot Nothing AndAlso Timer.Enabled Then
  30:                  Timer.Stop()
  31:                  WriteLog($"{Now} ReStart {vbCrLf}")
  32:                  Timer.Start()
  33:                  Await BuildCache()
  34:              End If
  35:          Catch Ex As Exception
  36:              EventLog.WriteEntry("PromocodeCacheCreater", "Exception in OnStop " & IIf(String.IsNullOrWhiteSpace(Ex.Message), "Empty", Ex.Message) & Environment.NewLine & Ex.StackTrace)
  37:              My.Computer.FileSystem.WriteAllText(My.Settings.OutPathRoot & "Index.htm", "Exception in OnStop " & IIf(String.IsNullOrWhiteSpace(Ex.Message), "Empty", Ex.Message) & Environment.NewLine & Ex.StackTrace, False)
  38:              WriteLog($"Exception in OnStop & {IIf(String.IsNullOrWhiteSpace(Ex.Message), "Empty", Ex.Message) & Environment.NewLine & Ex.StackTrace} {vbCrLf}")
  39:          End Try
  40:      End Sub
  41:   
  42:      Public Shared TargetServerPath As String
  43:      Public Shared TargetServerRoot As String
  44:      Public Shared UrlList As List(Of String)
  45:      Public Shared IsUrlCollected As Boolean = False
  46:   
  47:      Async Function BuildCache() As Task
  48:          WriteLog($"{Now} Start {vbCrLf}")
  49:          Dim Pos2 As Integer = My.Settings.CollectURL.LastIndexOf("/")
  50:          TargetServerPath = My.Settings.CollectURL.Substring(0, Pos2)
  51:          Dim TargetURI As Uri = New Uri(My.Settings.CollectURL)
  52:          TargetServerRoot = $"{TargetURI.Scheme}://{TargetURI.Host}"
  53:          Try
  54:              Dim HTML As String = Await ReadHtml(My.Settings.MainPage)
  55:              If String.IsNullOrEmpty(HTML) Then Return
  56:              UrlList = New List(Of String)
  57:              IsUrlCollected = False
  58:              Await Task.Run(Sub() ProcessingHTML(HTML))
  59:              My.Computer.FileSystem.WriteAllText(My.Settings.OutPathRoot & "Index.htm", HTML, False)
  60:              WriteLog($"{Now} cache created {My.Settings.OutPathRoot & "Index.htm"} ({HTML.Length} chars){vbCrLf}")
  61:          Catch ex As Exception
  62:              My.Computer.FileSystem.WriteAllText(My.Settings.OutPathRoot & "Index.htm", "Exception in BuildCache " & My.Settings.CollectURL & " " & IIf(String.IsNullOrWhiteSpace(ex.Message), "Empty", ex.Message) & Environment.NewLine & ex.StackTrace, False)
  63:              WriteLog($"Exception in BuildCache {My.Settings.CollectURL} {IIf(String.IsNullOrWhiteSpace(ex.Message), "Empty", ex.Message) & Environment.NewLine & ex.StackTrace} {vbCrLf}")
  64:          End Try
  65:          '
  66:          Try
  67:              Dim HTML As String = Await ReadHtml(My.Settings.CollectURL)
  68:              If String.IsNullOrEmpty(HTML) Then Return
  69:              UrlList = New List(Of String)
  70:              IsUrlCollected = True
  71:              Await Task.Run(Sub() ProcessingHTML(HTML))
  72:          Catch ex As Exception
  73:              WriteLog($"Exception in BuildCache {My.Settings.CollectURL} {IIf(String.IsNullOrWhiteSpace(ex.Message), "Empty", ex.Message) & Environment.NewLine & ex.StackTrace} {vbCrLf}")
  74:          End Try
  75:          '
  76:          UrlList.Sort()
  77:          WriteLog($"{Now} fount {UrlList.Count} URLs " & vbCrLf & $"{String.Join(",", UrlList)}" & vbCrLf)
  78:          '
  79:          Dim IISvDir As New List(Of String)
  80:          Dim PhysPath As New List(Of String)
  81:          IsUrlCollected = False
  82:          Dim J As Integer = 0
  83:          For Each OneLink As String In UrlList
  84:              If OneLink.StartsWith("/") And OneLink.Trim <> "/" And OneLink.Trim <> "#" And Not OneLink.Contains(vbCr) And Not OneLink.Contains(vbTab) And Not OneLink.Contains(vbLf) Then
  85:                  ' ++ debug
  86:                  'If J < 10 Then
  87:                  '    J += 1
  88:                  'Else
  89:                  '    Exit For
  90:                  'End If
  91:                  ' ++
  92:                  Dim CurLink As String = (My.Settings.MainPage & OneLink).Replace("//", "/").Replace("https:/", "https://").Replace("http:/", "http://")
  93:                  Dim CurDir As String = (My.Settings.OutPathRoot & OneLink.Replace("/", "\")).Replace("\\", "\")
  94:                  IISvDir.Add(OneLink)
  95:                  PhysPath.Add(CurDir)
  96:                  Debug.Print(CurLink)
  97:                  Try
  98:                      Dim HTML1 As String = Await ReadHtml(CurLink)
  99:                      Await Task.Run(Sub() ProcessingHTML(HTML1))
 100:                      If Not My.Computer.FileSystem.DirectoryExists(CurDir) Then
 101:                          My.Computer.FileSystem.CreateDirectory(CurDir)
 102:                      End If
 103:                      My.Computer.FileSystem.WriteAllText(CurDir & "Index.htm", HTML1, False)
 104:                      WriteLog($"{Now} cache created {CurDir & "Index.htm"} ({HTML1.Length} chars){vbCrLf}")
 105:                      HTML1 = Nothing
 106:                      Thread.Sleep(CInt(My.Settings.DelaySec) * 1000)
 107:                  Catch ex As Exception
 108:                      My.Computer.FileSystem.WriteAllText(CurDir & "Index.htm", "Exception in BuildCache " & CurLink & " " & IIf(String.IsNullOrWhiteSpace(ex.Message), "Empty", ex.Message) & Environment.NewLine & ex.StackTrace, False)
 109:                      WriteLog($"Exception in BuildCache {CurLink} {IIf(String.IsNullOrWhiteSpace(ex.Message), "Empty", ex.Message) & Environment.NewLine & ex.StackTrace} {vbCrLf}")
 110:                      Continue For
 111:                  End Try
 112:              End If
 113:          Next
 114:          '
 ...           '
 135:   
 136:      Sub WriteLog(Msg As String)
 137:          Dim Log As String = My.Computer.FileSystem.ReadAllText(My.Settings.LogFile)
 138:          Dim KolLines As Integer = Log.Count(Function(x) x = vbCr)
 139:          If KolLines > My.Settings.LogSize Then
 140:              Dim LastLinePos As Integer = Log.LastIndexOf(vbCr)
 141:              My.Computer.FileSystem.WriteAllText(My.Settings.LogFile, Log.Remove(0, LastLinePos), False)
 142:          End If
 143:          Log = Nothing
 144:          My.Computer.FileSystem.WriteAllText(My.Settings.LogFile, Msg, True)
 145:      End Sub
 146:   
 147:  End Class

There are a couple of trick for working with services. First is debugging. Directly debugging is impossible, there are need to replaces some code inside initialization.


Second trick is adding a two special service to run own code as service.


And last trick for working with service is installer service to system.



Example of windows service has been published to github https://github.com/Alex-1347/WindowsServiceExample

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