private void printDocument1_PrintPage(object sender, System.Drawing.Printing.PrintPageEventArgs e)
    {
        e.Graphics.DrawImage(bmp, 0, 0);
    }
    Bitmap bmp;


    private void btnPrint_Click(object sender, EventArgs e)
    {
        btnPrint.Hide();

        PrintDocument document = new PrintDocument();

        Graphics g = this.CreateGraphics();
        bmp = new Bitmap(this.Size.Width, this.Size.Height, g);
        Graphics mg = Graphics.FromImage(bmp);
        mg.CopyFromScreen(this.Location.X, this.Location.Y, 0, 0, this.Size);

        this.printDocument1.DefaultPageSettings.Landscape = true;


        printPreviewDialog1.Document = printDocument1;
        //printDocument1.DefaultPageSettings.PaperSize = new System.Drawing.Printing.PaperSize("PapperA4", 827, 1169);

        printPreviewDialog1.ShowDialog(calendar1);
        btnPrint.Show();
    }