httpclient请求返回值是乱码 (httpclient处理cookie)

最近在使用C# httpClient工具上传文件时，文件名为中文出现乱码的情况。部分代码如下

using (var content = new MultipartFormDataContent())
            {
                var stream = System.IO.File.OpenRead(filePath);
 
                var streamContent = new StreamContent(new FileStream(filePath, FileMode.Open, FileAccess.Read));
           
                content.Add(streamContent, "files[]", info.Name);

                var collections = new NameValueCollection();

                collections.Add("\"archtypeid\"", #34;{archtypeid}");
                collections.Add("\"archid\"", #34;{data["id"]}");

                collections.Add("\"tableid\"", #34;{tableid}");

                collections.Add("\"pl\"", #34;yes");
                collections.Add("\"userID\"", #34;{ConfigManage.Instance.UserId}"); 

                int time = ConvertDateTimeInt(DateTime.Now);
                collections.Add("\"timestamp\"", time.ToString());

                var formDatas = this.GetFormDataByteArrayContent(collections);

                foreach (var temp in formDatas)
                {
                    content.Add(temp);
                }

                var result = HttpClientHelper.Instance.Post(#34;Archive/ErecordManage/upload.html", content, null, null);

                if (int.TryParse(result.ToString(), out int val) && val == 1)
                {
                    //上传成功 
                    isUpLoadSucc = true;
                }
            }
       /// <summary>  
        /// 获取键值集合对应的ByteArrayContent集合  
        /// </summary>  
        /// <param name="collection"></param>  
        /// <returns></returns>  
        private List<ByteArrayContent> GetFormDataByteArrayContent(NameValueCollection collection)
        {
            List<ByteArrayContent> list = new List<ByteArrayContent>();
            foreach (var key in collection.AllKeys)
            {
                var dataContent = new ByteArrayContent(Encoding.UTF8.GetBytes(collection[key]));
                dataContent.Headers.ContentDisposition = new ContentDispositionHeaderValue("form-data")
                {
                    Name = key
                };
                list.Add(dataContent);
            }
            return list;
        }

解决办法为StreamContent设置头，代码如下

    //解决方案
                streamContent.Headers.Add("Content-Type", "application/octet-stream");
                String headerValue = "form-data; name=\"files[]\"; filename=\"" + info.Name + "\"";
                byte[] bytes = Encoding.UTF8.GetBytes(headerValue);
                headerValue = "";
                foreach (byte b in bytes)
                {
                    headerValue += (Char)b;
                }
                streamContent.Headers.Add("Content-Disposition", headerValue