C# 中实现 HTTP 请求使用 form-data 方式传递参数和文件_c# form-data

       public static string uploadRequest(Dictionary<string, object> dictParam, List<UploadFile> fileUrl, Encoding encoding, string url, string keyName)
        {
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
            WebHeaderCollection header = request.Headers;
            request.Method = "post";

            //定义请求流
            Stream myRequestStream = request.GetRequestStream();

            string Boundary = "--WebKitFormBoundary39B5a5e2FWoGbphs";
            //构造POST请求体
            StringBuilder PostContent = new StringBuilder("");

            //组成普通参数信息
            foreach (KeyValuePair<string, object> item in dictParam)
            {
                PostContent.Append("--" + Boundary + "\r\n")
                           .Append("Content-Disposition: form-data; name=\"" + item.Key + "\"" + "\r\n\r\n" + (string)item.Value + "\r\n");
            }
            byte[] PostContentByte = encoding.GetBytes(PostContent.ToString());
            myRequestStream.Write(PostContentByte, 0, PostContentByte.Length);//写入参数

            //文件
            for (int i = 0; i < fileUrl.Count; i++)
            {
                //读取文件信息
                FileStream fileStream = new FileStream(fileUrl[i].path, FileMode.Open, FileAccess.Read, FileShare.Read);
                byte[] bytes = new byte[fileStream.Length];
                fileStream.Read(bytes, 0, bytes.Length);
                fileStream.Close();
                byte[] UpdateFile = bytes;//转换为二进制

                //获取文件名称
                string filename = "";
                filename = Path.GetFileName(fileUrl[i].path);

                //处理文件参数信息
                StringBuilder FileContent = new StringBuilder();
                FileContent.Append("--" + Boundary + "\r\n")
                        .Append("Content-Disposition:form-data; name=\"" + keyName + "\";filename=\"" + filename + "\"" + "\r\n\r\n");
                byte[] FileContentByte = encoding.GetBytes(FileContent.ToString());
                request.ContentType = "multipart/form-data;boundary=" + Boundary;

                myRequestStream.Write(FileContentByte, 0, FileContentByte.Length);//写入文件信息
                myRequestStream.Write(UpdateFile, 0, UpdateFile.Length);//文件写入请求流中
            }

            byte[] ContentEnd = encoding.GetBytes("\r\n--" + Boundary + "--\r\n");//请求体末尾，后面会用到
            myRequestStream.Write(ContentEnd, 0, ContentEnd.Length);//写入结尾   
            myRequestStream.Close();

            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            string encodingth = response.ContentEncoding;
            if (encodingth == null || encodingth.Length < 1)
            {
                encodingth = "UTF-8"; //默认编码,根据需求自己指定 
            }
            StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.GetEncoding(encodingth));
            string retString = reader.ReadToEnd();
            return retString;
        }