I have a code to print labels in VB.NET (Visual Studio 2010), using the PrintDocument class, I have generated a class that contains what is necessary to print, plus the format of the label I am generating. When I print few labels (about 20) the code works without problems, but when I print 100 or more labels, the program throws an error, when executing the program in debug mode, I notice that the generated error is the following

  

System.AccessViolationException not checked
  HResult = -2147467261
   Message = Attempt to read or write to protected memory. Often, this indicates that there is another damaged memory.
   Source = System.Drawing

The error occurs in the prt_PrintPage function when wanting to assign the value of e.Graphics.DrawString.

I assume that I am bursting the buffer of the printer, but I do not know how to handle that error, or if this is indeed the reason for the error, I hope that someone can give me lights to correct this fault, thank you in advance.

My class to print with PrintDocument is this:

Imports System.Drawing.Printing
Imports System.Drawing.Text
Imports System.Threading.Thread

Public Class ImprimirPD

Private prtSettings As PrinterSettings
Private prtDoc As PrintDocument
Private prtFont As Font
Private barCodeFont As Font
Private CodeFont As Font
Private CompanyFont As Font
'
Private lineaActual As Integer

Private _datos As DataTable

Private _fileFontBarcode, _fileFontLabel As String

Public Sub New(ByVal fileFontBarcode As String, ByVal fileFontLabel As String)
    _fileFontBarcode = fileFontBarcode
    _fileFontLabel = fileFontLabel
    cargar_fuentes()
    ' La configuración actual de la impresora predeterminada
    prtSettings = New PrinterSettings
End Sub


 Region "Actions" 

Public Sub imprimir(ByVal datos As DataTable, ByVal selectAntes As Boolean, ByVal esPreview As Boolean)

    _datos = datos

    If prtSettings Is Nothing Then
        prtSettings = New PrinterSettings
        prtSettings.Collate = False
    End If
    '
    If selectAntes Then
        If seleccionarImpresora() = False Then Return
    End If
    '
    If prtDoc Is Nothing Then
        prtDoc = New PrintDocument
        AddHandler prtDoc.PrintPage, AddressOf prt_PrintPage
    End If
    '
    ' resetear la línea actual
    lineaActual = 0
    '
    'configuramos la hoja para imprimir
    Dim EPaperSize As New PaperSize("ETIQUETA", 410, 118)
    Dim EMargins As New Margins(100, 100, 100, 100)
    Dim EPrinterResolution As New PrinterResolution()
    EPrinterResolution.X = 203
    EPrinterResolution.Y = 203
    With prtSettings
        With .DefaultPageSettings
            .PaperSize = EPaperSize
            .Margins = EMargins
            .PrinterResolution = EPrinterResolution
            .Landscape = False
        End With
    End With

    ' la configuración a usar en la impresión
    prtDoc.PrinterSettings = prtSettings
    cargar_fuentes()

    If esPreview Then
        Dim prtPrev As New PrintPreviewDialog
        prtPrev.Document = prtDoc
        prtPrev.Text = "Previsualizar etiquetas"
        prtPrev.ShowDialog()
    Else
        prtDoc.Print()
    End If
End Sub

Public Function seleccionarImpresora() As Boolean
    Dim prtDialog As New PrintDialog
    If prtSettings Is Nothing Then
        prtSettings = New PrinterSettings
    End If

    With prtDialog
        .AllowPrintToFile = False
        .AllowSelection = False
        .AllowSomePages = False
        .PrintToFile = False
        .ShowHelp = False
        .ShowNetwork = True

        .PrinterSettings = prtSettings

        If .ShowDialog() = DialogResult.OK Then
            prtSettings = .PrinterSettings
        Else
            Return False
        End If

    End With

    Return True
End Function


 End Region 

 Region "Events" 

Private Sub prt_PrintPage(ByVal sender As Object, _
                          ByVal e As PrintPageEventArgs)
    ' Este evento se produce cada vez que se va a imprimir una página
    Dim fontHeight As Single
    Dim yPos As Single = e.MarginBounds.Top
    Dim leftMargin As Single = e.MarginBounds.Left
    Dim secBorder As Single
    Dim fila As DataRow
    fila = _datos.Rows(lineaActual)
    If fila(0) Then
        Dim strMascara, strOld, strDescrip, strLoteA As String
        Dim strFecha As Date
        strMascara = fila(1).ToString       'producto
        strOld = fila(2).ToString           'codigo_old
        strDescrip = fila(3).ToString       'descripcion
        strFecha = fila(4)                  'fecha_compra
        strLoteA = fila(9)                  'lote articulo
        leftMargin = 10
        secBorder = 80
        yPos = 10
        Dim Compañia, Dpart1, Dpart2, Dpart3 As String
        Dim largo As Integer = 50
        Compañia = "COMPAÑIA PRUEBA"
        If strDescrip.Length <= largo Then
            Dpart1 = strDescrip
            Dpart2 = ""
            Dpart3 = ""
        Else
            If strDescrip.Length <= largo * 2 Then
                Dpart1 = strDescrip.Substring(0, largo)
                Dpart2 = strDescrip.Substring(largo)
                Dpart3 = ""
            Else
                Dpart1 = strDescrip.Substring(0, largo)
                Dpart2 = strDescrip.Substring(largo, largo)
                Dpart3 = strDescrip.Substring(largo * 2)
            End If
        End If

        ' Asignar el tipo de letra
        fontHeight = 28 'CodeFont.GetHeight(e.Graphics) '27.76693


        ' imprimir cada una de las líneas de esta página
        e.Graphics.DrawString(Compañia, CompanyFont, Brushes.Black, leftMargin, yPos)
        e.Graphics.DrawString(strLoteA, CodeFont, Brushes.Black, 170, yPos)
        e.Graphics.DrawString(strMascara, CodeFont, Brushes.Black, 260, yPos)
        yPos += fontHeight

        fontHeight = 16 'prtFont.GetHeight(e.Graphics)  '15.61889

        'e.Graphics.DrawString("COD ANTIGUO : ", prtFont, Brushes.Black, leftMargin, yPos)
        'e.Graphics.DrawString(strOld, prtFont, Brushes.Black, secBorder, yPos)
        'yPos += fontHeight
        e.Graphics.DrawString("DESCRIPCION : ", prtFont, Brushes.Black, leftMargin, yPos)
        e.Graphics.DrawString(Dpart1, prtFont, Brushes.Black, secBorder, yPos)
        yPos += fontHeight
        e.Graphics.DrawString("             ", prtFont, Brushes.Black, leftMargin, yPos)
        e.Graphics.DrawString(Dpart2, prtFont, Brushes.Black, secBorder, yPos)
        yPos += fontHeight
        e.Graphics.DrawString("             ", prtFont, Brushes.Black, leftMargin, yPos)
        e.Graphics.DrawString(Dpart3, prtFont, Brushes.Black, secBorder, yPos)
        yPos += fontHeight


        e.Graphics.DrawString("Fecha Compra : ", prtFont, Brushes.Black, leftMargin, yPos)
        e.Graphics.DrawString(strFecha.ToString("dd/MM/yyyy"), prtFont, Brushes.Black, secBorder, yPos)
        yPos += fontHeight
        e.Graphics.DrawString("Lote Artic. : ", prtFont, Brushes.Black, leftMargin, yPos)
        e.Graphics.DrawString(strLoteA, prtFont, Brushes.Black, secBorder, yPos)
        yPos += fontHeight

        e.Graphics.DrawString(FormatBarCode(strMascara), barCodeFont, Brushes.Black, 130, 85)

    End If
    lineaActual += 1
    If lineaActual < _datos.Rows.Count Then
        e.HasMorePages = True
    Else
        e.HasMorePages = False
    End If
End Sub


 End Region 

 Region "Auxiliary" 

    Private Function FormatBarCode(ByVal code As String) As String
    Dim barcode As String = String.Empty
    barcode = String.Format("*{0}*", code)
    Return barcode
End Function

Private Sub cargar_fuentes()
    ' La fuente a usar en los codigos de Barra
    Dim pfc As PrivateFontCollection = New PrivateFontCollection()
    pfc.AddFontFile(_fileFontBarcode)
    Dim fontCBar As FontFamily = pfc.Families(0)
    barCodeFont = New Font(fontCBar, 30, FontStyle.Regular)

    pfc = New PrivateFontCollection()
    pfc.AddFontFile(_fileFontLabel)
    Dim fontLabel As FontFamily = pfc.Families(0)
    ' La fuente a usar en la impresión
    prtFont = New Font(fontLabel, 9, FontStyle.Bold)
    CompanyFont = New Font(fontLabel, 14, FontStyle.Bold)
    CodeFont = New Font(fontLabel, 16, FontStyle.Bold)
End Sub
     

End Region

End Class