C# Web 服务将存储为 BLOB 的 PDF 返回到 PDF

Question

我是 C#（和 Visual Studio）的新手。到目前为止，我已经成功部署了一个从本地 MSSQL 服务器读取数据的 WEB 服务，但我想使用 VS2010 对其进行扩展。

我有一个本地 mySQL 数据库，其中除其他数据外，还有一个存储 PDF 文件的 BLOB 列。我想阅读此 BLOB 列并从 Web 服务以 PDF 文件的形式返回结果。该服务将从 PHP 调用，在类似情况下，我可以毫不费力地呈现 PDF。

到目前为止，通过谷歌搜索，我能够读取数据并将其存储为本地文件。我不想将数据存储在文件中，而是将其存储在变量中（哪种类型？），这样我就可以将此变量作为 Web 服务的回复发送。

谢谢！

（我有很强的 PHP 背景，但我发现将这个背景“翻译”到 VS 有一些困难）

Answer 1

首先 - 为什么不是 VS2015？社区版是免费的并且支持扩展。没有理由活在过去:)

对于您的问题，我认为您只是缺少标题信息。

如果你把它作为 mime 类型添加到你的输出中，你应该可以回家了：

即：

var pdfBytes = DocumentRepository.GetPdfAsByteArray(myPdf);
context.Response.StatusCode = (int) HttpStatusCode.OK;
context.Response.ContentType = "application/pdf";
context.Response.OutputStream.Write(pdfBytes, 0, pdfBytes.Length);

Answer 2

你可以试试这个：

SqlConnection conn = new SqlConnection("Data Source=localhost;Integrated Security=SSPI;Initial Catalog=pubs;");
SqlCommand cmd = new SqlCommand("SELECT fileID, filePDF FROM myFiles", conn);   //filePDF is BLOB column

FileStream fs;                          // Writes the BLOB to a file
BinaryWriter bw;                        // Streams the BLOB to the FileStream object.

int bufferSize = 1000;                  // Max dimension of your PDF file in bytes.
byte[] outbyte = new byte[bufferSize];  // The BLOB byte[] buffer to be filled by GetBytes.
long retval;                            // The bytes returned from GetBytes.
long startIndex = 0;                    // The starting position in the BLOB output.

string fileID = "";                     // The publisher id to use in the file name.

// Open the connection and read data into the DataReader.
conn.Open();
SqlDataReader myReader = cmd.ExecuteReader(CommandBehavior.SequentialAccess);

while (myReader.Read())
{
  fileID = myReader.GetString(0);  

  fs = new FileStream("file_pdf" + fileID + ".pdf", FileMode.OpenOrCreate, FileAccess.Write);
  bw = new BinaryWriter(fs);

  startIndex = 0;

  retval = myReader.GetBytes(1, startIndex, outbyte, 0, bufferSize);

  while (retval == bufferSize)
  {
    bw.Write(outbyte);
    bw.Flush();

    startIndex += bufferSize;
    retval = myReader.GetBytes(1, startIndex, outbyte, 0, bufferSize);
  }

  bw.Write(outbyte, 0, (int)retval - 1);
  bw.Flush();

  bw.Close();
  fs.Close();
}

myReader.Close();
conn.Disponse();
conn.Close();

Answer 3

结合此处的一些信息和其他答案，我设法解决了我的问题。通常，我想避免将 BLOB 中的 PDF 作为物理文件写入，然后必须将其作为文件打开和读取。感谢您的帮助！

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.ServiceModel.Web;
using System.Text;
using System.Configuration;
using MySql.Data.MySqlClient;
using System.IO;

public MySqlConnection myInit()
{
    return new MySqlConnection(
        "host=" + ConfigurationManager.AppSettings["mysqlHost"] +
        ";user=" + ConfigurationManager.AppSettings["mysqlUser"] +
        ";password=" + ConfigurationManager.AppSettings["mysqlPass"] +
        ";database=" + ConfigurationManager.AppSettings["mysqlDb"]);
}

public Dictionary<string,byte[]> getPDF(int pdfid)
{
    string query = "SELECT md5_string, data FROM pdf,pdf_view WHERE pdf.id=" + pdfid + " and pdf_view.id=pdf.id";
    MySqlConnection con = myInit();
    MySqlCommand cmd = new MySqlCommand(query, con);

    MemoryStream ms;
    BinaryWriter bw;                        // Streams the BLOB to the MemoryStream object.
    Dictionary<string, byte[]> result = new Dictionary<string, byte[]>();

    int bufferSize = 1000;                   // Size of the BLOB buffer.
    byte[] outbyte = new byte[bufferSize];  // The BLOB byte[] buffer to be filled by GetBytes.
    long retval;                            // The bytes returned from GetBytes.
    long startIndex = 0;

    con.Open();

    MySqlDataReader myReader = cmd.ExecuteReader(System.Data.CommandBehavior.SequentialAccess);

    while (myReader.Read())
    {
        ms = new MemoryStream();
        bw = new BinaryWriter(ms);

        string md5 = myReader.GetString(0);

        // Reset the starting byte for the new BLOB.
        startIndex = 0;

        // Read the bytes into outbyte[] and retain the number of bytes returned.
        retval = myReader.GetBytes(1, startIndex, outbyte, 0, bufferSize);

        // Continue reading and writing while there are bytes beyond the size of the buffer.
        while (retval == bufferSize)
        {
            bw.Write(outbyte);
            bw.Flush();

            // Reposition the start index to the end of the last buffer and fill the buffer.
            startIndex += bufferSize;
            retval = myReader.GetBytes(1, startIndex, outbyte, 0, bufferSize);
        }

        // Write the remaining buffer.
        bw.Write(outbyte, 0, (int)retval - 1);
        bw.Flush();

        result.Add(md5, ms.ToArray());

        // Close the output stream.
        bw.Close();
        ms.Close();
    }

    // Close the reader and the connection.
    myReader.Close();
    con.Close();

    return result;
}

我将它与 PHP 一起使用，如下所示：

$o = new SoapClient('http://localhost:3153/IntranetConnect.svc?wsdl', array('trace' => 0, 'cache_wsdl' => WSDL_CACHE_NONE));
$pdf = $o->getPDF(array('pdfid' => 1109));

foreach($pdf->getPDFResult as $value) {
   header("Content-type: application/pdf");
   header('Content-disposition: filename='.$value->Key.'.pdf');
   echo $value->Value;
}