Printing Is Coming Blank while PrintPreview Shows The Result In C# Windows Application

// Print the document's pages.
        private int NextPageNum = 0;

// Result of the Event 'PrintPage'
 private void prnDocument_PrintPage(object sender, System.Drawing.Printing.PrintPageEventArgs e)
        {
               
            float pageWidth = e.PageSettings.PrintableArea.Width;
            float pageHeight = e.PageSettings.PrintableArea.Height;

            leftMargin = (int)e.MarginBounds.Left;
            rightMargin = (int)e.MarginBounds.Right;
            topMargin = (int)e.MarginBounds.Top;
            bottomMargin = (int)e.MarginBounds.Bottom;
            InvoiceWidth = (int)e.MarginBounds.Width;
            InvoiceHeight = (int)e.MarginBounds.Height;

            switch (NextPageNum)
            {
                case 0:
                    RectangleF rectF1 = new RectangleF(90, 45, pageWidth-85, pageHeight-35);
                    Pen rectPen = new Pen(System.Drawing.Color.Black, 1);
                    e.Graphics.DrawRectangle(rectPen, Rectangle.Round(rectF1));

                    RectangleF rectF2 = new RectangleF(95, 230, pageWidth - 95, pageHeight - 225);
                    //Pen rectPen = new Pen(System.Drawing.Color.Black, 2);
                    e.Graphics.DrawRectangle(rectPen, Rectangle.Round(rectF2));

                    SetInvoiceHead(e.Graphics); // Draw Invoice Head
                    SetOrderData(e.Graphics); // Draw Order Data
                    SetInvoiceData(e.Graphics, e); // Draw Invoice Data
                    break;
                case 1:
                    ImageShower(e.Graphics);
                    break;
            }
            // Next time print the next page.
            NextPageNum += 1;

            // We have more pages if we have not yet printed page 2.
            e.HasMorePages = (NextPageNum <2);
      }

private void prnDocument_BeginPrint(object sender, PrintEventArgs e)
        {
            // Start with page 0.
            NextPageNum = 0;
        }

private void btnPreview_Click(object sender, EventArgs e)
        {
           
            NextPageNum = 0;
            retriveData();
            foreBrush = FontforeColor();
            prnPreview.Document = prnDocument;
            ((Form)prnPreview).WindowState = FormWindowState.Maximized;
            // To Display 100% Preview
            prnPreview.PrintPreviewControl.StartPage = 0;
            prnPreview.PrintPreviewControl.Zoom = 1.0;
            prnPreview.PrintPreviewControl.Columns = 1;
            prnPreview.ShowDialog();
       }

private void btnPrint_Click(object sender, EventArgs e)
       {
          
           try
           {
               prnDocument.Print();
           }
           catch (Exception e)
           {
               MessageBox.Show(e.ToString());
           }
       }