System.NullReferenceException: Object reference not set to an instance of an object when running as a Service

Question

I'm trying to run a service that calls a sub from a class (pop3.vb) but I always get system.NullReferenceException errors:

System.NullReferenceException: Object reference not set to an instance of an object.
   at Auto_PrintEmailAttachment.POP3.POPConnect(String strServer, String strUserName, String strPassword)
   at Auto_PrintEmailAttachment.AutoPrintEmailAttachment.OnTimedEvent(Object source, ElapsedEventArgs e)

When I'm running the same code (except the service starting part) in a windows form app, everything runs fine.

The service sub in POP3.vb starts with: 
Sub POPConnect(ByVal strServer As String, ByVal strUserName As String, ByVal strPassword As String)

...

end sub

The AutoPrinter.vb has the start service and timer commands. The service is started with this:

Protected Overrides Sub OnStart(ByVal args() As String)
        'Create eventviewer entries
        If Not System.Diagnostics.EventLog.SourceExists("Test Auto Print Email Attachment Service") Then
            System.Diagnostics.EventLog.CreateEventSource("Test Auto Print Email Attachment Service",
            "Test")
        End If
        EventLog1.Source = "Test Auto Print Email Attachment Service"
        EventLog1.Log = "Test"

        NotifyIcon1.Visible = True
        NotifyIcon1.ShowBalloonTip(3000, "Test", "Test Auto Print Email Attachment Service is started", ToolTipIcon.Info)


        Try

            aTimer.Enabled = True
            EventLog1.WriteEntry("Service Started.")

        Catch ex As Exception
            EventLog1.WriteEntry(ex.ToString)
            Exit Try
        Finally
        End Try


    End Sub

The AutoPrinter.vb has also the initialization part:

    Public Sub New()
        MyBase.New()
        InitializeComponent()

        'Create eventviewer entries
        If Not System.Diagnostics.EventLog.SourceExists("Test Auto Print Email Attachment Service") Then
            System.Diagnostics.EventLog.CreateEventSource("Test Auto Print Email Attachment Service",
            "Test")
        End If
        EventLog1.Source = "Test Auto Print Email Attachment Service"
        EventLog1.Log = "Test"

        Try
            aTimer = New System.Timers.Timer(10000)
            AddHandler aTimer.Elapsed, AddressOf OnTimedEvent
            aTimer.Interval = My.Settings.checkinterval_milliseconds

            'System.Configuration.ConfigurationManager.AppSettings("checkinterval_milliseconds")

            'CREATE WORKING DIRECTORY
            If Directory.Exists((Environ("HOMEPATH") & "\Documents\") & "TestEmailAutoPrintAttachment") = False Then
                Directory.CreateDirectory((Environ("HOMEPATH") & "\Documents\") & "TestEmailAutoPrintAttachment")
            End If

            'CREATE WORKING SUBDIRECTORY (PRINTED FILES)
            If Directory.Exists((Environ("HOMEPATH") & "\Documents\") & "TestEmailAutoPrintAttachment\SentToPrinter") = False Then
                Directory.CreateDirectory((Environ("HOMEPATH") & "\Documents\") & "TestEmailAutoPrintAttachment\SentToPrinter")
            End If

        Catch ex As Exception
            EventLog1.WriteEntry(ex.ToString)
            Exit Try
        Finally
        End Try
    End Sub

also in AutoPrinter.vb, there's the OnTimedEvent sub that's called

Private Sub OnTimedEvent(source As Object, e As ElapsedEventArgs)

        EventLog1.WriteEntry("Timed events initiated.")

        Try


            'variable declaration
            Dim strServer, strUsername, strPassword, strFrom, strSubject, strToo, strBody, strMailContent As String
            Dim popConn As Auto_PrintEmailAttachment.POP3
            Dim mailMess As Auto_PrintEmailAttachment.EmailMessage
            Dim intMessCnt, i As Integer



            'set the variables to the input boxes
            strServer = My.Settings.pop3server.ToString()
            'System.Configuration.ConfigurationManager.AppSettings("pop3server")

            strUsername = My.Settings.mailboxusername.ToString()
            'System.Configuration.ConfigurationManager.AppSettings("mailboxusername")

            strPassword = My.Settings.mailboxpassword.ToString()
            'System.Configuration.ConfigurationManager.AppSettings("mailboxpassword")

            'make sure some detials have been filled in
            If strServer = "" Then
                EventLog1.WriteEntry("No Mail server specified!")
                Exit Sub
            End If
            If IsNothing(strServer) = True Then
                EventLog1.WriteEntry("Mailserver is NULL!")
            End If

            If strUsername = "" Then
                EventLog1.WriteEntry("No Username specified!")
                Exit Sub
            End If
            If IsNothing(strUsername) = True Then
                EventLog1.WriteEntry("Username is NULL!")
            End If

            If strPassword = "" Then
                EventLog1.WriteEntry("No Password Specified!")
                Exit Sub
            End If
            If IsNothing(strPassword) = True Then
                EventLog1.WriteEntry("Password is NULL!")
            End If


            'create the objects
            popConn = New Auto_PrintEmailAttachment.POP3
            mailMess = New Auto_PrintEmailAttachment.EmailMessage

            'if we have got to this point, try and connect to the server
            popConn.POPConnect(strServer, strUsername, strPassword)

            'now we have a connection, see if there are any mails on the server
            intMessCnt = popConn.GetMailStat()

            'now, see if we have returned any messages
            If intMessCnt > 0 Then



                'if we returned some messages, loop through each one and get the details
                For i = 1 To intMessCnt


                    'load the entire content of the mail into a string
                    strMailContent = popConn.GetMailMessage(i)

                    'call the functions to get the various parts out of the email 
                    strFrom = mailMess.ParseEmail(strMailContent, "From:")
                    strSubject = mailMess.ParseEmail(strMailContent, "Subject:")
                    strToo = mailMess.ParseEmail(strMailContent, "To:")

                    'My.Computer.FileSystem.WriteAllText("C:\Temp\emails\strSubject.txt", strSubject & vbNewLine & strFrom, False)

                    If Not strSubject.IndexOf(My.Settings.subjectstringtosearch.ToString) = -1 Then
                        strBody = mailMess.ParseBody()

                        ' 
                        'My.Computer.FileSystem.WriteAllText("C:\Temp\emails\messages.txt", strBody, False)

                    End If

                Next i
            End If

            'Quit the connection to the server
            popConn.CloseConn()

        Catch ex As Exception
            EventLog1.WriteEntry(ex.ToString)

            Exit Try
        Finally
        End Try

    End Sub


End Class

It does work when i run the code via a windows form, so I must be doing something wrong with the starting and stopping?

Thanks,
Davy

Answer 1

my guess is that EventLog1 is null in OnTimedEvent. Try reinitializing it if it doesn't already exist. I suspect that the onstart/onstop may affect a different instance of the class. just a hunch, but worth a quick try.

Answer 2

Hi,

The ontimedevent sets the "timed event started" eventlog entry.

How can I check if the onstart/onstop affects a different instance of the class?

the only reference to the class file (that i can see(newbie dev)) is via Dim popConn As Auto_PrintEmailAttachment.POP3

Thanks,

D

Answer 3

Hi,

I found something (not yet the total solution yet I think :))

I tried to add eventlogPOP3.WriteEntry("test") in the POP3 class, but that resulted in the same error.

When I commented the evenlog init lines, then the error was gone. Somehow services run more "protected" on the OS than regular windows forms apps I think.

'Class to connect to the passed mail server on port 110
    Sub POPConnect(ByVal strServer As String, ByVal strUserName As String, ByVal strPassword As String)
        'If Not System.Diagnostics.EventLog.SourceExists("Inscope Auto Print Email Attachment Service") Then
        '    System.Diagnostics.EventLog.CreateEventSource("Inscope Auto Print Email Attachment Service",
        '    "Inscope")
        'End If
        'eventlogPOP3.Source = "Inscope Auto Print Email Attachment Service"
        'eventlogPOP3.Log = "Inscope"

Regards,

Davy

Answer 4

I'm not seeing a place in your code where you instantiate the EventLog1 object. I was thinking somthing like this. Create a method to return eventlog1, which will always ensure that it is instantiated and initialized. then replace your instances of eventlog1 with GetEventLog().

Services do run differantly than windows apps, but you can configure what user the service runs under in services.msc after its been installed, or via your ServiceProcessInstaller.Account property.

'this must be run as admin under UAC, or within a service. otherwise it will throw a security exception
public Function GetEventLog() as Diagnostics.EventLog
	if isnothing(EventLog1) then
		If Not System.Diagnostics.EventLog.SourceExists("Test Auto Print Email Attachment Service") Then
			System.Diagnostics.EventLog.CreateEventSource("Test Auto Print Email Attachment Service", "Test")
		End If
		EventLog1 = new EventLog("Test", ".", "Test Auto Print Email Attachment Service")
	end if
	return EventLog1
End Function

Private Sub OnTimedEvent(source As Object, e As ElapsedEventArgs)
        GetEventLog().WriteEntry("Timed events initiated.")
        Try
            ....

            'make sure some detials have been filled in
            If strServer = "" Then
                GetEventLog().WriteEntry("No Mail server specified!")
                Exit Sub
            End If
            If IsNothing(strServer) = True Then
                GetEventLog().WriteEntry("Mailserver is NULL!")
            End If

	    ....
End Sub

Answer 5

Hi,

The event log entries are working when they are in the main service.vb

'Create eventviewer entries
        If Not System.Diagnostics.EventLog.SourceExists("Test Auto Print Email Attachment Service") Then
            System.Diagnostics.EventLog.CreateEventSource("Test Auto Print Email Attachment Service",
            "Test")
        End If
        EventLog1.Source = "Test Auto Print Email Attachment Service"
        EventLog1.Log = "Test"

and all below entries in that same services.vb also result in an eventvwr entry being added:

EventLog1.WriteEntry("Service Started.")

However, I would like to add events as well from the POP3.vb class. But there it doesn't seem to work.

I can't drag the eventvwr element from the tools into that vb. What is the other way? Do I have to put the eventvwr function in a different class and refer that?

Thanks,

Davy

Answer 6

if pop3 is being called by teh service.vb file, its rights should be the same as those that service.vb had, so thats weird. it is being invoked by the service, correct? what user account is your service running under?

I would never bother dragging an evntlog object onto the form, since asside from declaring the variable 'private EventLog1 as EventLog', you have already done all the work in code anyway.

have you tried passing a live eventlog isntance into pop3, instead of instantiating it there?

Answer 7

Hi Davy,

Do you have any updates?

Best regards,

---

Mike Feng
MSDN Community Support | Feedback to us
Please remember to mark the replies as answers if they help and unmark them if they provide no help.

Answer 8

Hi,

If I put the below code in:

Dim Eventlog1 As New EventLog
        Eventlog1.Source = "Tes Auto Print Email Attachment Service"
        Eventlog1.Log = "Test"
        Eventlog1.WriteEntry((Environ("HOMEPATH") & "\Documents\") & "TestEmailAutoPrintAttachment\SentToPrinter\" & pdfdocumentname.ToString, EventLogEntryType.Information)

Then I have eventlog entries originating from the POP3.vb

So it works, Thanks !!!! :)