批量 多个JPG生产PDF .net C#

using iTextSharp.text;
using iTextSharp.text.pdf;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Text;

using System.Windows.Forms;

namespace JGP2PDF
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            try
            {

                OpenFileDialog op = new OpenFileDialog();
                op.Multiselect = true;
                op.Filter = "标签 | *.jpg";
                if (op.ShowDialog() == DialogResult.OK)
                {
                    var filenames = op.FileNames;
                    ConvertJPG2PDF(filenames, textBox2.Text);
                    MessageBox.Show("导出成功！");
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
                throw ex;
            }

        }

        private static void ConvertJPG2PDF(string[] jpgfiles, string pdf)
        {
            var document = new Document(iTextSharp.text.PageSize.A4, , , , );
            using (var stream = new FileStream(pdf, FileMode.Create, FileAccess.Write, FileShare.None))
            {
                PdfWriter.GetInstance(document, stream);
                document.Open();
                foreach (var jpgfile in jpgfiles)
                {
                    using (var imageStream = new FileStream(jpgfile, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
                    {
                        var image = iTextSharp.text.Image.GetInstance(imageStream);
                        if (image.Height > iTextSharp.text.PageSize.A4.Height)
                        {
                            image.ScaleToFit(iTextSharp.text.PageSize.A4.Width, iTextSharp.text.PageSize.A4.Height);
                        }
                        else if (image.Width > iTextSharp.text.PageSize.A4.Width)
                        {
                            image.ScaleToFit(iTextSharp.text.PageSize.A4.Width, iTextSharp.text.PageSize.A4.Height);
                        }
                        image.Alignment = iTextSharp.text.Image.ALIGN_MIDDLE;
                        document.Add(image);
                    }
                }

                document.Close();

            }
        }
    }

}