关于webrequest上传文件的问题

[rebelboy]

下面是我在网上找的一段代码，我通过webrequest提交后，接收那边收到的数据大小和我发送的一样，但是无法获取到附件里的文件。


这是调用的代码

        CookieContainer cookies = new CookieContainer();
        //add or use cookies    
        NameValueCollection querystring = new NameValueCollection();
        querystring["uname"] = "uname";
        querystring["passwd"] = "snake3";
        string uploadfile;// set to file to upload    
        uploadfile = "c:\\test.jpg";

        //everything except upload file and url can be left blank if needed    
        string outdata = UploadFileEx(uploadfile,
             "http://img.nextgame.cn/upload.ashx", "uploadfile", "image/pjpeg",
             querystring, cookies);
        Response.Write(outdata);

这是代码

    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);
        webrequest.CookieContainer = cookies;
        webrequest.ContentType = "multipart/form-data; boundary=" + boundary;
        webrequest.Method = "POST";
        webrequest.UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.2; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.648; .NET CLR 3.5.21022)";

        // Build up the post message header    
        StringBuilder sb = new StringBuilder();
        sb.Append("--");
        sb.Append(boundary);
        sb.Append("");
        sb.Append("Content-Disposition: form-data; name=\"");
        sb.Append(fileFormName);
        sb.Append("\"; filename=\"");
        sb.Append(Path.GetFileName(uploadfile));
        sb.Append("\"");
        sb.Append("");
        sb.Append("Content-Type: ");
        sb.Append(contenttype);
        sb.Append("");
        sb.Append("");

        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("--" + boundary + "");

        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);

        requestStream.Flush();//清空


        WebResponse responce = webrequest.GetResponse();
        Stream s = responce.GetResponseStream();
        StreamReader sr = new StreamReader(s);

        return sr.ReadToEnd();
    }   

[Jerry_hu]

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