Implementation method of exporting pdf in C# (draw directly without previewing)

[HttpGet]
    public HttpResponseMessage ExportPdf(string id)
    {
      string pdfName = "";
　//id query conditions, modify them according to actual situation　//pdfName For example      byte[] pdfData= _policyGapManagerService.ExportPdf(id, out pdfName);//Get pdf bytes      var result = new HttpResponseMessage()
      {
        Content = new ByteArrayContent(pdfData)
      };
       =
        new ContentDispositionHeaderValue("attachment")
        {
          FileName = pdfName
        };
       =new MediaTypeHeaderValue("application/pdf");
      return result;
    }

#region Call local file to return pdfbyte array
    /// <summary>
    /// Call the local file to return the pdfbyte array    /// </summary>
    /// <param name="srcPdfFile">‘D:\'</param>
    /// <returns></returns>

    public static byte[] GetSignaturePDFByte(string srcPdfFile)
    {
      using (FileStream fsRead = new FileStream(srcPdfFile, , , ))
      {
        int fsLen = (int);
        byte[] hebyte = new byte[fsLen];
        (hebyte, 0, );
        return hebyte;
      }
    }

    #endregion Call local file to return pdfbyte array
    #region Download pdf from the website and convert it into byte stream

    /// <summary>
    /// Download the pdf from the website and convert it into a byte stream    /// </summary>
    /// <param name="srcPdfFile">File address: 'https://******/group2/M00/00/04/'</param>
    /// &lt;returns&gt;&lt;/returns&gt;
    public static Byte[] GetByteByRemoteURL(string srcPdfFile)
    {
      byte[] arraryByte;
      HttpWebRequest req = (HttpWebRequest)(srcPdfFile);
       = "GET";
      using (WebResponse wr = ())
      {
        StreamReader responseStream = new StreamReader((), Encoding.UTF8);
        int length = (int);
        byte[] bs = new byte[length];

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

        //Read to memory        MemoryStream stmMemory = new MemoryStream();
        byte[] buffer1 = new byte[length];
        int i;
        //Put bytes one by one into Byte        while ((i = (buffer1, 0, )) &gt; 0)
        {
          (buffer1, 0, i);
        }
        arraryByte = ();
        ();
      }
      return arraryByte;
    }

    #endregion Download pdf from the website and convert it into byte stream
    #region Download the file from the website and save it to another path
    /// &lt;summary&gt;
    /// Download the file from the website and save it to another path    /// &lt;/summary&gt;
    /// <param name="pdfFile">File address</param>    /// <param name="saveLoadFile">Save file path: D:\</param>    /// &lt;returns&gt;&lt;/returns&gt;
    public string SaveRemoteFile( string saveLoadFile , string pdfFile)
    {
      //bool flag = false;
      var f = saveLoadFile + ().ToString("D") + ".pdf";
      Uri downUri = new Uri(pdfFile);
      //Create a WEB request and return the HttpWebRequest object      HttpWebRequest hwr = (HttpWebRequest)(downUri);
      //The stream object is automatically closed after use      using (Stream stream = ().GetResponseStream())
      {
        //File stream, stream information is read into the file stream, close after reading        using (FileStream fs = (f))
        {
          //Create a byte group and set its size to what bytes          byte[] bytes = new byte[102400];
          int n = 1;
          while (n &gt; 0)
          {
            //How many bytes are read from the stream at a time and assign the value to N. After reading, N is 0 and exits the loop            n = (bytes, 0, 10240);
            (bytes, 0, n);　//Write the stream information of the specified bytes into the file stream          }
        }
      }

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

    #endregion Download files from the website，Save to another path

/// <summary>
    /// Download the FTP file.    /// </summary>
    /// <param name="offsetPath">Relative Path</param>    /// <param name="fileName">File name</param>    /// <returns>Download results, local file path</returns>    public string DownLoad(string offsetPath,string fileName)
    {
      try
      {
        FtpWebRequest ftpWeb = (FtpWebRequest)(_ftpRootPath + offsetPath + fileName);
         = ;
         = true;
        var resp = ();
        using (FileStream fs = new FileStream(_outPath + fileName, ))
        {
          using (var s = ())
          {
            if (s == null) { return "The file does not exist!"; }

            int readCout = 0;
            byte[] bytes = new byte[1024];
            readCout = (bytes, 0, 1024);
            while (readCout &gt; 0)
            {
              (bytes, 0, readCout);
              readCout = (bytes, 0, 1024);
            }
          }
        }
        ();
        return _outPath + fileName;
      }
      catch (Exception e)
      {
        return ;
      }
      
    }

    /// &lt;summary&gt;
    /// Determine whether the file exists    /// &lt;/summary&gt;
    /// &lt;param name="offsetPath"&gt;&lt;/param&gt;
    /// &lt;param name="fileName"&gt;&lt;/param&gt;
    /// &lt;returns&gt;&lt;/returns&gt;
    public bool FileExists(string offsetPath, string fileName)
    {
      try
      {
        FtpWebRequest ftpWeb = (FtpWebRequest)(_ftpRootPath + offsetPath + fileName);
         = ;
         = true;
        var resp = (FtpWebResponse)();
        ();
        return true;
      }
      catch (Exception)
      {
        return false;
      }
    }

    /// &lt;summary&gt;
    /// Get all files in the directory    /// &lt;/summary&gt;
    /// &lt;returns&gt;&lt;/returns&gt;
    public string[] Files(string offsetPath)
    {
      try
      {
        FtpWebRequest ftpWeb = (FtpWebRequest)(_ftpRootPath + offsetPath);
         = ;
        Stream stream = ().GetResponseStream();
        if (stream == null)
        {
          return null;
        }
        List&lt;string&gt; fileList = new List&lt;string&gt;();
        using (StreamReader sr = new StreamReader(stream))
        {
          StringBuilder sb = new StringBuilder();
          do
          {
            (());
            if ( &gt; 0)
            {
              (());
              ();
            }
            else
            {
              break;
            }
          } while (true);
        }
        return ();
      }
      catch (Exception)
      {
         return null;
      }
    }