C# 合并PDF文件

C# 合并PDF文件

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using iTextSharp.text;
using iTextSharp.text.pdf;

namespace MEAS.Common
{
    public class PdfHelper
    {
        //定义一个用于保存静态变量的实例
        private static PdfHelper instance = null;
        //定义一个保证线程同步的标识
        private static readonly object locker = new object();
        //构造函数为私有，使外界不能创建该类的实例
        private PdfHelper() { }
        public static PdfHelper Instance
        {
            get
            {
                if (instance == null)
                {
                    lock (locker)
                    {
                        if (instance == null) instance = new PdfHelper();
                    }
                }
                return instance;
            }
        }

        /// <summary>
        /// 合并PDF文件
        /// </summary>
        /// <param name="fileList">需要合并的PDF五年级</param>
        /// <param name="outMergeFile">合并后文件路径</param>
        public string MergePDFFiles(string[] fileList, string mergeFile)
        {
            PdfReader reader;
            Document document = new Document();
            PdfWriter writer = PdfWriter.GetInstance(document, new FileStream(mergeFile, FileMode.Create));
            document.Open();
            PdfContentByte cb = writer.DirectContent;
            PdfImportedPage newPage;
            for (int i = 0; i < fileList.Length; i++)
            {
                reader = new PdfReader(fileList[i]);
                int iPageNum = reader.NumberOfPages;
                for (int j = 1; j <= iPageNum; j++)
                {
                    document.NewPage();
                    newPage = writer.GetImportedPage(reader, j);
                    cb.AddTemplate(newPage, 0, 0);
                }
            }
            document.Close();

            return mergeFile;
        }

    }
}