Printing previous Invoice

Question

I'm having problem in printing previous invoice not the current one this happens almost 4 times a day, printing around 10000 vouchers per day can anyone explain me why?
First i update data by using ExecuteScalar and getting Auto-Gen Number from Database
Then I'm Updating Invoice Number to another Table for Invoice numbering system
TicketNumberUpdate()
lbl_Status.Text = "Updating Ticket Number..."
Application.DoEvents()
System.Threading.Thread.Sleep(200)
then i wait and filter according to my ticket number and populate data to richtextbox 
PrintFunc(" WHERE dbo.tbl_Tickets.TicketNo='" & txtTicket.Text & "' AND dbo.tbl_Tickets.Ticket_Type='" & cboTicketType.Text.Trim & "'")
lbl_Status.Text = "Loading Ticket ..."
Application.DoEvents()
System.Threading.Thread.Sleep(200)
and save that html text to temporary html file 
rtb_TicketFormat.Rtf = rtb_TicketFormat.Rtf.Replace("Duplicate.png", "Original.png")
Dim myFileName As String = IO.Path.Combine(IO.Path.GetTempPath, "_.html")
rtb_TicketFormat.SaveFile(myFileName, RichTextBoxStreamType.PlainText)
lbl_Status.Text = "Printing Ticket ..."
Application.DoEvents()
System.Threading.Thread.Sleep(200)
and wait for Save that Invoice in html format after that i call for PrintTktz for printing that file
Private Sub PrintTktz()
Dim webBrowserForPrinting As New WebBrowser()
AddHandler webBrowserForPrinting.DocumentCompleted, New _
WebBrowserDocumentCompletedEventHandler(AddressOf PrintDocumentz)
webBrowserForPrinting.Url = New Uri(IO.Path.GetTempPath & "_.html")
End Sub
Private Sub PrintDocumentz(ByVal sender As Object, _
ByVal e As WebBrowserDocumentCompletedEventArgs)
Dim webBrowserForPrinting As WebBrowser = CType(sender, WebBrowser)
webBrowserForPrinting.ScriptErrorsSuppressed = True
webBrowserForPrinting.Print()
webBrowserForPrinting.Dispose()
End Sub
when testing this works fine do you guys think some time when printing if below code could not save the file it gives that error? 
rtb_TicketFormat.SaveFile(myFileName, RichTextBoxStreamType.PlainText)
Thank you every one for you kind help!...

Answer 1

I'm not certain. However from the code you display you are constantly creating a WebBrowser object then never disposing of it when you are done with it. So I would imagine at some point your applications memory is getting really high as you seem to create
10,000 of them a day or something. Which means 10,000 created objects doing nothing and never to be used again are sitting in your applications memory.
The code is "Dim webBrowserForPrinting As New WebBrowser()".
It's possible the code for the sub PrintTktz could be altered as below which should dispose of the WebBrowser object when the code is done with it. But you will need to test it obviously. There's two subs. One has a Using statement which may not work and
the other has a loop that runs until the WebBrowser finishes. Both may not work really.
If neither work the issue still needs to be corrected. Of course if the loop runs for a long time the UI could freeze. And if the end using statement occurs prior to the WebBrowser loading well that's not good either of course.
WebBrowser.IsBusy
Private Sub PrintTktz()
Using webBrowserForPrinting As New WebBrowser()
AddHandler webBrowserForPrinting.DocumentCompleted, New _
WebBrowserDocumentCompletedEventHandler(AddressOf PrintDocumentz)
webBrowserForPrinting.Url = New Uri(IO.Path.GetTempPath & "_.html")
End Using
End Sub
Private Sub PrintTktz()
Dim webBrowserForPrinting As New WebBrowser()
AddHandler webBrowserForPrinting.DocumentCompleted, New _
WebBrowserDocumentCompletedEventHandler(AddressOf PrintDocumentz)
webBrowserForPrinting.Url = New Uri(IO.Path.GetTempPath & "_.html")
Do Until WebBrowserForPrint.IsBusy = False
Loop
webBrowserForPrinting.Dispose()
End Sub
La vida loca