C# 導出pdf（瀏覽器不預覽直接下載）

一.接口部分的代碼

        [HttpGet]
        public HttpResponseMessage ExportPdf(string id)
        {
            string pdfName = "";
　　　　　　　//id 查詢條件，根據實際情況修改即可
　　　　　　　//pdfName 例如download.pdf
            byte[] pdfData= _policyGapManagerService.ExportPdf(id, out pdfName);//獲得pdf字節
            var result = new HttpResponseMessage(HttpStatusCode.OK)
            {
                Content = new ByteArrayContent(pdfData)
            };
            result.Content.Headers.ContentDisposition =
                new ContentDispositionHeaderValue("attachment")
                {
                    FileName = pdfName
                };
            result.Content.Headers.ContentType =new MediaTypeHeaderValue("application/pdf");
            return result;
        }

二.返回pdfbyte數組

1.下載http模式的pdf文件（以ASP.NET爲例，將PDF存在項目的目錄下，可以通過http直接打開項目下的pdf文件）

#region 調用本地文件使用返回pdfbyte數組

        /// <summary>
        /// 調用本地文件使用返回pdfbyte數組
        /// </summary>
        /// <param name="srcPdfFile">‘D:\in2434341555551.pdf’</param>
        /// <returns></returns>

        public static byte[] GetSignaturePDFByte(string srcPdfFile)
        {
            using (FileStream fsRead = new FileStream(srcPdfFile, FileMode.Open, FileAccess.Read, FileShare.Read))
            {
                int fsLen = (int)fsRead.Length;
                byte[] hebyte = new byte[fsLen];
                fsRead.Read(hebyte, 0, hebyte.Length);
                return hebyte;
            }
        }

        #endregion 調用本地文件使用返回pdfbyte數組

        #region 從網站上下載pdf，轉化爲字節流


        /// <summary>
        /// 從網站上下載pdf，轉化爲字節流
        /// </summary>
        /// <param name="srcPdfFile">文件地址：'https://******/group2/M00/00/04/wKj-mlpcoZ2IUbK5AACrpaV6k98AAAB6gAAAAAAAKu9562.pdf'</param>

        /// <returns></returns>
        public static Byte[] GetByteByRemoteURL(string srcPdfFile)
        {
            byte[] arraryByte;
            HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(srcPdfFile);
            req.Method = "GET";
            using (WebResponse wr = req.GetResponse())
            {
                StreamReader responseStream = new StreamReader(wr.GetResponseStream(), Encoding.UTF8);
                int length = (int)wr.ContentLength;
                byte[] bs = new byte[length];

                HttpWebResponse response = wr as HttpWebResponse;
                Stream stream = response.GetResponseStream();

                //讀取到內存
                MemoryStream stmMemory = new MemoryStream();
                byte[] buffer1 = new byte[length];
                int i;
                //將字節逐個放入到Byte 中
                while ((i = stream.Read(buffer1, 0, buffer1.Length)) > 0)
                {
                    stmMemory.Write(buffer1, 0, i);
                }
                arraryByte = stmMemory.ToArray();
                stmMemory.Close();
            }
            return arraryByte;
        }

        #endregion 從網站上下載pdf，轉化爲字節流

        #region 從網站上下載文件，保存到其他路徑

        /// <summary>
        /// 從網站上下載文件，保存到其他路徑
        /// </summary>
        /// <param name="pdfFile">文件地址</param>
        /// <param name="saveLoadFile">保存文件路徑：D:\12221.pdf</param>
        /// <returns></returns>
        public string SaveRemoteFile( string saveLoadFile , string pdfFile)
        {
            //bool flag = false;
            var f = saveLoadFile + Guid.NewGuid().ToString("D") + ".pdf";
            Uri downUri = new Uri(pdfFile);
            //建立一個ＷＥＢ請求，返回HttpWebRequest對象
            HttpWebRequest hwr = (HttpWebRequest)WebRequest.Create(downUri);
            //流對象使用完後自動關閉
            using (Stream stream = hwr.GetResponse().GetResponseStream())
            {
                //文件流，流信息讀到文件流中，讀完關閉
                using (FileStream fs = File.Create(f))
                {
                    //建立字節組，並設置它的大小是多少字節
                    byte[] bytes = new byte[102400];
                    int n = 1;
                    while (n > 0)
                    {
                        //一次從流中讀多少字節，並把值賦給Ｎ，當讀完後，Ｎ爲０,並退出循環
                        n = stream.Read(bytes, 0, 10240);
                        fs.Write(bytes, 0, n);　//將指定字節的流信息寫入文件流中
                    }
                }
            }

            //return flag;
            //return _outPath + saveLoadFile;
            return f;
        }

        #endregion 從網站上下載文件，保存到其他路徑

2.ftp模式的pdf文件

/// <summary>
        /// 下載FTP文件。
        /// </summary>
        /// <param name="offsetPath">相對路徑</param>
        /// <param name="fileName">文件名稱</param>
        /// <returns>下載結果，本地文件路徑</returns>
        public string DownLoad(string offsetPath,string fileName)
        {
            try
            {
                FtpWebRequest ftpWeb = (FtpWebRequest)WebRequest.Create(_ftpRootPath + offsetPath + fileName);
                ftpWeb.Method = WebRequestMethods.Ftp.DownloadFile;
                ftpWeb.UseBinary = true;
                var resp = ftpWeb.GetResponse();
                using (FileStream fs = new FileStream(_outPath + fileName, FileMode.Create))
                {
                    using (var s = resp.GetResponseStream())
                    {
                        if (s == null) { return "文件不存在!"; }

                        int readCout = 0;
                        byte[] bytes = new byte[1024];
                        readCout = s.Read(bytes, 0, 1024);
                        while (readCout > 0)
                        {
                            fs.Write(bytes, 0, readCout);
                            readCout = s.Read(bytes, 0, 1024);
                        }
                    }
                }
                resp.Close();
                return _outPath + fileName;
            }
            catch (Exception e)
            {
                return e.Message;
            }
            
        }

        /// <summary>
        /// 判斷文件是否存在
        /// </summary>
        /// <param name="offsetPath"></param>
        /// <param name="fileName"></param>
        /// <returns></returns>
        public bool FileExists(string offsetPath, string fileName)
        {
            try
            {
                FtpWebRequest ftpWeb = (FtpWebRequest)WebRequest.Create(_ftpRootPath + offsetPath + fileName);
                ftpWeb.Method = WebRequestMethods.Ftp.DownloadFile;
                ftpWeb.UseBinary = true;
                var resp = (FtpWebResponse)ftpWeb.GetResponse();
                resp.Close();
                return true;
            }
            catch (Exception)
            {
                return false;
            }
        }

        /// <summary>
        /// 獲取目錄下所有文件
        /// </summary>
        /// <returns></returns>
        public string[] Files(string offsetPath)
        {
            try
            {
                FtpWebRequest ftpWeb = (FtpWebRequest)WebRequest.Create(_ftpRootPath + offsetPath);
                ftpWeb.Method = WebRequestMethods.Ftp.ListDirectory;
                Stream stream = ftpWeb.GetResponse().GetResponseStream();
                if (stream == null)
                {
                    return null;
                }
                List<string> fileList = new List<string>();
                using (StreamReader sr = new StreamReader(stream))
                {
                    StringBuilder sb = new StringBuilder();
                    do
                    {
                        sb.Append(sr.ReadLine());
                        if (sb.Length > 0)
                        {
                            fileList.Add(sb.ToString());
                            sb.Clear();
                        }
                        else
                        {
                            break;
                        }
                    } while (true);
                }
                return fileList.ToArray();
            }
            catch (Exception)
            {
                 return null;
            }
        }