物體賦值例外：未將物件參考設定到物件的實體。-有解無憂

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace FK.SendMessageService.ServiceData.MessageContent
{
    public class ArticlesItem
    {
        /// <summary>
        /// 標題
        /// </summary>
        public string title { get; set; }
        /// <summary>
        /// 描述
        /// </summary>
        public string description { get; set; }
        /// <summary>
        /// 點擊后跳轉的鏈接
        /// </summary>
        public string url { get; set; }
        /// <summary>
        /// 圖文訊息的圖片鏈接，支持JPG、PNG格式，較好的效果為大圖 1068*455，小圖150*150
        /// </summary>
        public string picurl { get; set; }
    }

    public class News
    {
        /// <summary>
        /// 圖文訊息，一個圖文訊息支持1到8條圖文
        /// </summary>
        public List<ArticlesItem> articles { get; set; }
    }

    public class Send_Img
    {
        /// <summary>
        /// 成員ID串列
        /// </summary>
        public string touser { get; set; }
        /// <summary>
        /// 部門ID串列
        /// </summary>
        public string toparty { get; set; }
        /// <summary>
        /// 標簽ID串列
        /// </summary>
        public string totag { get; set; }
        /// <summary>
        /// 訊息型別，此時固定為：news
        /// </summary>
        public string msgtype { get; set; }
        /// <summary>
        /// 企業應用的id
        /// </summary>
        public int agentid { get; set; }
        /// <summary>
        ///
        /// </summary>
        public News news { get; set; }
        /// <summary>
        /// 表示是否開啟id轉譯
        /// </summary>
        public int enable_id_trans { get; set; }
        /// <summary>
        /// 表示是否開啟重復訊息檢查，0表示否，1表示是，默認0
        /// </summary>
        public int enable_duplicate_check { get; set; }
        /// <summary>
        /// 表示是否重復訊息檢查的時間間隔，默認1800s，最大不超過4小時
        /// </summary>
        //public int duplicate_check_interval { get; set; }
    }
}

using FK.SendMessageService.ServiceData.Common;
using Newtonsoft.Json.Linq;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using FK.SendMessageService.ServiceData.MessageContent;

namespace FK.SendMessageService.ServiceData.Send
{
    public class Send_Image: News
    {
        Wechat_Access_Token Toke = new Wechat_Access_Token();

        //企業ID
        private string Appid = ConfigHelper.GetConfigStr("Appid");
        //應用憑證密鑰
        private string Secret = ConfigHelper.GetConfigStr("Secret");
        //應用ID
        private int Agentid = int.Parse(ConfigHelper.GetConfigStr("Agentid"));

        public object GetSend_Image()
        {
            object json = new { };

            try
            {
                //1.獲取access_token
                string token = Toke.GetObtainToken(Appid, Secret);

                if (token != "")
                {
                    List<ArticlesItem> articleslist = new List<ArticlesItem>();
                    ArticlesItem articles = new ArticlesItem();
                    articles.title = "中秋節禮品領取";
                    articles.description = "今年中秋節公司有豪禮相送";
                    articles.url = "http://23005732cx.51mypc.cn/Login.html";
                    articles.picurl = "/Image/春節卡片.jpg";
                    articleslist.Add(articles);

                    Send_Img image = new Send_Img();
                    image.touser = "PengYinCong";
                    image.toparty = "";
                    image.totag = "";
                    image.msgtype = "news";
                    image.agentid = Agentid;
                    image.news.articles = articleslist;
                    image.enable_id_trans = 0;
                    image.enable_duplicate_check = 0;

                    string paramjsonStr = SerializeHelper.JsonSerialize(image);

                    string Url = "https://qyapi.weixin.qq.com/cgi-bin/message/send?";
                    StringBuilder UserStr = new StringBuilder();
                    UserStr.Append(Url);
                    UserStr.Append("access_token=" + token + "");

                    //3.使用post請求訪問企業微信推送訊息的介面
                    string UserResult = HttpUtils.DoPost(UserStr.ToString(), paramjsonStr).ToString();
                    dynamic jsonUser = JToken.Parse(UserResult) as dynamic;
                    Log.CreateLogManager().Error("獲取用戶企業微信狀態為：" + jsonUser["errcode"]);

                    if (jsonUser["errcode"] == 0)
                    {
                        json = new { Success = true, Msg = "發送成功" };
                    }
                    else
                    {
                        json = new { Success = false, Msg = "發送失敗" };
                    }
                }
                else
                {
                    json = new { Success = false, Msg = "access_token獲取失敗" };
                }
            }
            catch (Exception ex)
            {
                json = new { Success = false, Msg = "出現例外" };
                Log.CreateLogManager().Error("給企業微信用戶推送訊息出錯：" + ex);
            }

            return json;
        }
    }
}

出現例外未知：