C# HttpWebRequest 表单上传

Posted 2023-02-24

【中文标题】C# HttpWebRequest 表单上传

【英文标题】：C# HttpWebRequest form upload

【发布时间】：2012-10-17 14:35:52

【问题描述】：

我正在尝试从我的 C# 程序自动上传文件。这是上传文件的方法。

public static string UploadFileEx(string uploadfile, string url,
                            string fileFormName, string contenttype, NameValueCollection querystring,
                            CookieContainer cookies)
    
        if ((fileFormName == null) ||
            (fileFormName.Length == 0))
        
            fileFormName = "file";
        

        if ((contenttype == null) ||
            (contenttype.Length == 0))
        
            contenttype = "application/octet-stream";
        


        string postdata;
        postdata = "";
        if (querystring != null)
        
            foreach (string key in querystring.Keys)
            
                postdata += key + "=" + querystring.Get(key) + "&";
            
        
        Uri uri = new Uri(url + postdata);

        string boundary = "----------" + DateTime.Now.Ticks.ToString("x");
        HttpWebRequest webrequest = (HttpWebRequest)WebRequest.Create(uri);

        var sp = webrequest.ServicePoint;
        var prop = sp.GetType().GetProperty("HttpBehaviour", BindingFlags.Instance | BindingFlags.NonPublic);
        prop.SetValue(sp, (byte)0, null);

        webrequest.CookieContainer = cookies;
        webrequest.ContentType = "multipart/form-data; boundary=" + boundary;
        webrequest.Method = "POST";

        webrequest.KeepAlive = true;
        webrequest.Referer = "http://www.iwi.hs-karlsruhe.de/scs/simulate/upload.jsp";
        webrequest.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";
        webrequest.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.1 (KHTML, like Gecko) Chrome/13.0.782.220 Safari/535.1";
        webrequest.Headers.Add("Accept-Language:de-de,de;q=0.8,en-us;q=0.5,en;q=0.3");
        webrequest.Headers.Add("Accept-Encoding:gzip, deflate");
        webrequest.ProtocolVersion = HttpVersion.Version11;


        // Build up the post message header

        StringBuilder sb = new StringBuilder();
        sb.Append("--");
        sb.Append(boundary);
        sb.Append("\r\n");
        sb.Append("Content-Disposition: form-data; name=\"");
        sb.Append(fileFormName);
        sb.Append("\"; filename=\"");
        sb.Append(Path.GetFileName(uploadfile));
        sb.Append("\"");
        sb.Append("\r\n");
        sb.Append("Content-Type: ");
        sb.Append(contenttype);
        sb.Append("\r\n");
        sb.Append("\r\n");

        string postHeader = sb.ToString();
        byte[] postHeaderBytes = Encoding.UTF8.GetBytes(postHeader);

        // Build the trailing boundary string as a byte array

        // ensuring the boundary appears on a line by itself

        byte[] boundaryBytes =
               Encoding.ASCII.GetBytes("\r\n--" + boundary + "--\r\n");

        FileStream fileStream = new FileStream(uploadfile,
                                    FileMode.Open, FileAccess.Read);
        long length = postHeaderBytes.Length + fileStream.Length +
                                               boundaryBytes.Length;
        webrequest.ContentLength = length;

        Stream requestStream = webrequest.GetRequestStream();

        // Write out our post header

        requestStream.Write(postHeaderBytes, 0, postHeaderBytes.Length);

        // Write out the file contents

        byte[] buffer = new Byte[checked((uint)Math.Min(4096,
                                 (int)fileStream.Length))];
        int bytesRead = 0;
        while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)
            requestStream.Write(buffer, 0, bytesRead);

        // Write out the trailing boundary

        requestStream.Write(boundaryBytes, 0, boundaryBytes.Length);
        try
        
            WebResponse responce = webrequest.GetResponse();
            Stream s = responce.GetResponseStream();
            StreamReader sr = new StreamReader(s);

            return sr.ReadToEnd();
        
        catch (Exception ex)
        
            return ex.Message;
        

    

当我在示例图片上传页面上这样称呼它时，一切正常：

string outdata = UploadFileEx(uploadfile,
             "http://www.minpic.de/upload_file.php", "uploadfile0", "image/jpg",
             null, null);

但是当我尝试将其上传到我高中的页面时，它不起作用。上传页面由登录表单保护。所以我调用上传页面来获取初始 Cookie，我发布登录凭据并获得正确的结果。所以我可以看到以下上传表单：

<form action="../simulate" method=post enctype="multipart/form-data"><br />Choose your inputdata file (xml).<br /><input type=file size=50 maxlength=100000 name="Datei" accept="text/xml"><br><br><input type=submit value="Send"></form>

然后当我发布图片时（我知道预期的类型是 xml，但页面回答了我在这种情况下想要的错误......）我的上传函数返回错误代码 500。这是wireshark 对浏览器的说明帖子：

POST /scs/simulate HTTP/1.1 主持人：某位主持人 连接：保持活动 内容长度：3874 缓存控制：max-age=0 出处：同一主机 用户代理：Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.79 Safari/537.4 内容类型：multipart/form-data；边界=----WebKitFormBoundaryP3Ti6rxYcN1ov7JD 接受：text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8 参考：一些网址 接受编码：gzip、deflate、sdch 接受语言：de-DE,de;q=0.8,en-US;q=0.6,en;q=0.4 接受字符集：ISO-8859-1,utf-8;q=0.7,*;q=0.3 饼干：SCS_COOKIE=默认=DE$$MarkePlaceLang=DE； JSESSIONID=B459541362241F66D9312AF157262D25

这里是来自 c# 的帖子：

POST 同上 内容类型：multipart/form-data；边界=---------8cf828671b8365c 参考：一些网址 接受：text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8 用户代理：Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.1 (KHTML, like Gecko) Chrome/13.0.782.220 Safari/535.1 接受语言：de-de,de;q=0.8,en-us;q=0.5,en;q=0.3 接受编码：gzip，放气 主机：与上面相同的主机 Cookie：JSESSIONID=FFE0B7530FFE6A3C8F15FD8A900865B0 内容长度：3847 期望：100-继续 连接：保持活动状态

我能看到的唯一区别是 Expect: 100-continue ... 数据包大小有问题吗？

提前致谢。

【参考方案1】：

您必须使用分段上传。这显示在您的浏览器帖子中：

   Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryP3Ti6rxYcN1ov7JD

这是一个例子： Upload files with HTTPWebrequest (multipart/form-data)

这是有道理的，因为通常图像大小可能大于通常帖子的限制（2KB 或 4KB，我忘了）。

【讨论】：

但我在浏览器和 C# 帖子中都有“Content-Type: multipart/form-data”。