while function using System.Drawing.Printing adds nothing?

Question

I would like help on a report I am creating via code...

Next in the data insertion part taking from a datagridview I’m in trouble, when I use the command While on the page printPreview appears the searched data, but when I launch the command to print it no data is printed, only header and footer. But when I use the command For it works perfectly, however I can not add more than 1 page because of the For.

Private Sub PrintDocument1_PrintPage(ByVal sender As Object, ByVal e As System.Drawing.Printing.PrintPageEventArgs) Handles pdoc.PrintPage
    'Margens
    Dim margemEsq As Single = e.MarginBounds.Left
    Dim margemSup As Single = e.MarginBounds.Top
    Dim margemDir As Single = e.MarginBounds.Right
    Dim margemInf As Single = e.MarginBounds.Bottom

    'Fontes
    Dim fonteTitulo As Font
    Dim fonteRodape As Font
    Dim fonteNormal As Font

    fonteTitulo = New Font("Verdana", 15, FontStyle.Bold)
    fonteRodape = New Font("Verdana", 8)
    fonteNormal = New Font("Verdana", 10)

    'Linhas
    Dim caneta As New Pen(Color.Black, 1)
    'e.Graphics.DrawLine(caneta, margemEsq, 60, margemDir, 60)
    e.Graphics.DrawImage(Image.FromFile("C:\" & "vb.gif"), 100, 68)
    'e.Graphics.DrawLine(caneta, margemEsq, 160, margemDir, 160)
    'e.Graphics.DrawString("Catálogo de Produtos", fonteTitulo, Brushes.Blue, margemEsq + 275, 80, New StringFormat())


    'impressão do titulo das colunas
    Dim fonteColuna As New Font("Arial", 16)
    e.Graphics.DrawString("Código", fonteColuna, Brushes.Red, margemEsq, 140, New StringFormat())
    e.Graphics.DrawString("Produto", fonteColuna, Brushes.Red, margemEsq + 100, 140, New StringFormat())
    e.Graphics.DrawString("Preço", fonteColuna, Brushes.Red, margemEsq + 500, 140, New StringFormat())
    e.Graphics.DrawLine(caneta, margemEsq, 170, margemDir, 170)

    Dim linhasPorPagina = e.MarginBounds.Height / fonteNormal.GetHeight(e.Graphics) - 6
    Dim linhaAtual = 1
    ' While num < DataGridView1.RowCount - 1
    ' ou
    'for num < DataGridView1.RowCount - 1
    Dim posicaoDaLinha = margemSup + (linhaAtual * fonteNormal.GetHeight(e.Graphics) + 70)
    Dim strings As String = DataGridView1.Rows(num).Cells(0).Value.ToString()
    e.Graphics.DrawString(strings, fonteNormal, Brushes.Black, margemEsq, posicaoDaLinha, New StringFormat())
    linhaAtual += 1
    '----------------------------
    e.Graphics.DrawLine(caneta, margemEsq, margemInf, margemDir, margemInf)
    e.Graphics.DrawString(System.DateTime.Now, fonteRodape, Brushes.Black, margemEsq, margemInf, New StringFormat())
    e.Graphics.DrawString("Pag. " & paginaAtual.ToString, fonteRodape, Brushes.Black, margemDir - 50, margemInf, New StringFormat())
    paginaAtual += 1
End Sub