微信永久视频上传报错41005 媒体文件丢失

Question

@using (Html.BeginForm("UploadVideo", "AddForeverVideo", FormMethod.Post, new { enctype = "multipart/form-data" })) {
选择上传媒体文件：





}
上面是一个input type为file ，name=“description” id=“description”还有一个submit提交按钮
---------------------------------
上面是前台页面
-------------------------------------------------------------
///
/// 这个借口没有通过
///
///
///
public ActionResult UploadVideo(FormCollection collection)
{
string result = "";
HttpPostedFileBase file = Request.Files[0];
string access_token = pub.GetExistAccessToken();
string localpath = "D:\Simple\MyTest\image\" + file.FileName;
file.SaveAs(localpath);//保存本地用于数据库
result = WXApi.AddForeverVideo(access_token, file, "video");

return Content(result);
}
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上面是控制器代码
------------------------------
public static string MaterialUploads(string accessToken, HttpPostedFileBase isFile, string materialType, string title = "", string introduction = "")
{
string url = "https://api.weixin.qq.com/cgi-bin/material/add_material?access_token={0}&type={1}";
url = string.Format(url, accessToken, materialType);

        //设置提交表单的名称
        string formName = materialType == "video" ? "description" : "media";

        byte[] datas = null;

        #region 组合正文
        //换行
        string CRLF = "\r\n";

        //边界标识
        string Identification = "----" + DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss");

        try
        {
            //生成表单信息
            StringBuilder sb = new StringBuilder();
            sb.Append("--");
            sb.Append(Identification);
            sb.Append(CRLF);
            sb.Append("Content-Disposition: form-data; id=\"" + formName + "\"; name=\"" + formName + "\"; filename=\"" + isFile.FileName + "\"");
            sb.Append(CRLF);
            sb.Append("Content-Type: " + isFile.ContentType.ToLower() + "");
            sb.Append(CRLF);
            sb.Append(CRLF);

            //如果是视频数据，就添加视频标题与视频的描述信息
            if (materialType.ToLower() == "video")
            {
                sb.Append(" description=\"{\"title\":\"" + title + "\", \"introduction\":\"" + introduction + "\"}\"");
                sb.Append(CRLF);
                sb.Append(CRLF);
            }

            //头部与尾部
            string header = sb.ToString();
            string foot = CRLF + "--" + Identification + "--" + CRLF;

            //转为byte[]流
            byte[] headerbytes = Encoding.UTF8.GetBytes(header);
            byte[] footbytes = Encoding.UTF8.GetBytes(foot);

            List<byte> datalist = new List<byte>();

            //转换为btye[]数据流
            Stream stream = isFile.InputStream;
            byte[] data = new byte[stream.Length];
            stream.Read(data, 0, data.Length);

            // 设置当前流的位置为流的开始 
            stream.Seek(0, SeekOrigin.Begin);

            datalist.AddRange(headerbytes);
            datalist.AddRange(data);
            datalist.AddRange(footbytes);

            //组合完整的流数据
            datas = datalist.ToArray<byte>();
        }
        catch (Exception)
        {
            return "正文组合失败";
        }
        #endregion

        return MaterialUploadd(datas, url, Identification);
    }