c# - 如何从 HTTP 流中组装 pdf？

Question

我正在使用第 3 方 html 到 pdf 的转换 (DocRaptor)。您将您的 HTML 发布到他们的站点，他们以 PDF 响应。他们给你的起始代码工作正常，但它把文件放到你的硬盘上。我修改了他们的代码以使其通过浏览器并作为文件下载。所以我 100% 确信我从 HTTP 响应中获得的数据是好的数据。我似乎无法将它组装回可用文件。

我有理由相信问题在于我如何处理 responseStream 数据。一旦我进入 Try/Catch，一切似乎都出错了。我对 c# 和 web 编程很陌生，所以我非常感谢这里的 SO 用户提供的一些指导。谢谢。这是我的代码。

            string postData = String.Format(PostFormat,
            (string.IsNullOrEmpty(DocumentContent) ? "document_url" : "document_content"),
            HttpUtility.UrlEncode(string.IsNullOrEmpty(DocumentContent) ? DocumentURL : DocumentContent),
            HttpUtility.UrlEncode(Name),
            HttpUtility.UrlEncode(type),
            HttpUtility.UrlEncode(Test.ToString().ToLower()),
            HttpUtility.UrlEncode(Strict),
            HttpUtility.UrlEncode(PrinceOptions));

        var byteArray = Encoding.UTF8.GetBytes(postData);

        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(DocRaptorUrl);
        request.Method = "POST";
        request.ContentType = "application/x-www-form-urlencoded";
        request.ContentLength = byteArray.Length;
        using (var dataStream = request.GetRequestStream()) { dataStream.Write(byteArray, 0, byteArray.Length); }

        System.IO.Stream stream = null;

        try 
        {
            using (HttpWebResponse httpResponse = (HttpWebResponse)request.GetResponse())
            {
                using (System.IO.Stream responseStream = httpResponse.GetResponseStream())
                {

                    var filepath = @"C:\Users\David\Downloads\UberwriterUSRReport.pdf";
                    HttpContext.Current.Response.ContentType = "application/pdf";

                    // let the browser know how to open the PDF document, attachment or inline, and the file name
                    HttpContext.Current.Response.AddHeader("Content-Disposition", String.Format("attachment; filename=UberwriterUSRReport.pdf"));

                    stream = new System.IO.FileStream(filepath, System.IO.FileMode.Create);

                    CopyStream(responseStream, stream);

                    long bytestToRead = stream.Length;

                    while (bytestToRead > 0)
                    {
                        if (HttpContext.Current.Response.IsClientConnected)
                        {
                            byte[] buffer = new Byte[10000];  
                            int length = stream.Read(buffer, 0, 10000);
                            HttpContext.Current.Response.OutputStream.Write(buffer, 0, length);
                            HttpContext.Current.Response.Flush();

                            bytestToRead = bytestToRead - length;
                        }
                        else
                        {
                            bytestToRead = -1;
                        }
                    }
                }
            }
        }

Answer 1

您是否打算在将文件发送到浏览器之前将文件保存到硬盘？因为这就是您现在(错误地)在做的事情。

最好是将写入操作包含在 using 语句中，因为我没有看到您在任何地方关闭流:

stream = new System.IO.FileStream(filepath, System.IO.FileMode.Create);

此处您要保存到文件:

CopyStream(responseStream, stream);

接下来，您将尝试读取您的输出流(您刚刚保存文件时使用的输出流)，以将其写入您的 Response.Outputstream。并且您已经完成了复制流实现，那么为什么要在这里手动执行呢？ :

HttpContext.Current.Response.OutputStream.Write(buffer, 0, length);

所以，我会说它应该是这样的:

using (HttpWebResponse httpResponse = (HttpWebResponse)request.GetResponse())
{
    using (System.IO.Stream responseStream = httpResponse.GetResponseStream())
    {
        var filepath = @"C:\Users\David\Downloads\UberwriterUSRReport.pdf";
        HttpContext.Current.Response.ContentType = "application/pdf";

        // let the browser know how to open the PDF document, attachment or inline, and the file name
        HttpContext.Current.Response.AddHeader("Content-Disposition", String.Format("attachment; filename=UberwriterUSRReport.pdf"));

        using (var stream = new System.IO.FileStream(filepath, System.IO.FileMode.Create)) {
          CopyStream(responseStream, stream);
        }

        using (var readstream = new System.IO.FileStream(filepath, System.IO.FileMode.Read)) {
            CopyStream(readstream, HttpContext.Current.Response.OutputStream);
        }
    }
}

或者，如果您根本不想将文件保存在服务器上:

using (HttpWebResponse httpResponse = (HttpWebResponse)request.GetResponse())
{
    using (System.IO.Stream responseStream = httpResponse.GetResponseStream())
    {
        // let the browser know how to open the PDF document, attachment or inline, and the file name
        HttpContext.Current.Response.AddHeader("Content-Disposition", String.Format("attachment; filename=UberwriterUSRReport.pdf"));

      CopyStream(responseStream, HttpContext.Current.Response.OutputStream);
    }
}