HttpWebRequest post上传文件

  public static string HttpUploadFile(string url, string path)
    {
        // 设置参数 
        HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
        CookieContainer cookieContainer = new CookieContainer();
        request.CookieContainer = cookieContainer;
        request.AllowAutoRedirect = true;
        request.Method = "POST";
        string boundary = DateTime.Now.Ticks.ToString("X"); // 随机分隔线 
        request.ContentType = "multipart/form-data;charset=utf-8;boundary=" + boundary;
        byte[] itemBoundaryBytes = Encoding.UTF8.GetBytes("\r\n--" + boundary + "\r\n");
        byte[] endBoundaryBytes = Encoding.UTF8.GetBytes("\r\n--" + boundary + "--\r\n");

        int pos = path.LastIndexOf("\\");
        string fileName = path.Substring(pos + 1);

        //请求头部信息  
        StringBuilder sbHeader = new StringBuilder(string.Format("Content-Disposition:form-data;name=\"file\";filename=\"{0}\"\r\nContent-Type:application/octet-stream\r\n\r\n", fileName));
        byte[] postHeaderBytes = Encoding.UTF8.GetBytes(sbHeader.ToString());

        FileStream fs = new FileStream(path, FileMode.Open, FileAccess.Read);
        byte[] bArr = new byte[fs.Length];
        fs.Read(bArr, 0, bArr.Length);
        fs.Close();

        Stream postStream = request.GetRequestStream();
        postStream.Write(itemBoundaryBytes, 0, itemBoundaryBytes.Length);
        postStream.Write(postHeaderBytes, 0, postHeaderBytes.Length);
        postStream.Write(bArr, 0, bArr.Length);
        postStream.Write(endBoundaryBytes, 0, endBoundaryBytes.Length);
        postStream.Close();

        //发送请求并获取相应回应数据 
        HttpWebResponse response = request.GetResponse() as HttpWebResponse;
        //直到request.GetResponse()程序才开始向目标网页发送Post请求 
        Stream instream = response.GetResponseStream();
        StreamReader sr = new StreamReader(instream, Encoding.UTF8);
        //返回结果网页（html）代码 
        string content = sr.ReadToEnd();
        return content;
    }