vb.net中的打印预览为空

这是我的代码：

Imports System.Drawing
Imports System.Drawing.Printing
Imports System.Data
Imports System.Data.OleDb
Public Class Form3
Dim dgv As New DataGridView()
Dim print As New PrintDocument()
Dim preview As New PrintPreviewDialog()
Private Sub Form3_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    Dim con As New OleDbConnection("Provider=Microsoft.Jet.Oledb.4.0;Data Source=C:\Users\user\Documents\Inventory\InventoryLogin\InventoryLogin\Supplies.mdb")
    Try
        con.Open()
        Dim sql As String
        sql = "SELECT * From [product info]"
        Dim adapter As New OleDbDataAdapter(sql, con)
        Dim dt As New DataTable("product info")
        adapter.Fill(dt)

        preview.PrintPreviewControl.Zoom = 1
        preview.Document = print
        preview.Show()

        AddHandler print.PrintPage, AddressOf print_PrintPage

    Catch Ex As Exception
        MessageBox.Show(Ex.Message)
    End Try

End Sub

Protected Sub print_PrintPage(ByVal sender As Object, ByVal e As PrintPageEventArgs)
    Dim ColumnCount As Integer = dgv.ColumnCount
    Dim RowCount As Integer = dgv.RowCount

    Dim CellTopPos As Integer = print.PrinterSettings.DefaultPageSettings.Margins.Top

    For Row = 0 To RowCount - 2

        Dim CellLeftPos As Integer = print.PrinterSettings.DefaultPageSettings.Margins.Left

        For Cell = 0 To ColumnCount - 1

            Dim CellValue As String = dgv.Rows(Row).Cells(Cell).Value.ToString()
            Dim CellWidth = dgv.Rows(Row).Cells(Cell).Size.Width + 10
            Dim CellHeight = dgv.Rows(Row).Cells(Cell).Size.Height

            Dim Brush As New SolidBrush(Color.Black)
            e.Graphics.DrawString(CellValue, New Font("tahoma", 10), Brush, CellLeftPos, CellTopPos)
            e.Graphics.DrawRectangle(Pens.Black, CellLeftPos, CellTopPos, CellWidth, CellHeight)

            CellLeftPos += CellWidth
        Next

        CellTopPos += dgv.Rows(Row).Cells(0).Size.Height
    Next

End Sub
End Class

我正在尝试在vb.net中的datagridview中预览和打印项目 . 用户需要在打印前单击“打印预览”按钮查看文档，但是当我单击按钮时，它只显示一个空页面 . 如何使datagridview中的记录出现在我的预览页面中？