企业消息，不定时的出错

HttpClient client = new HttpClient();
        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));


        string url = "https://oapi.dingtalk.com/message/send?access_token=" + AccessTokenId;


    
        var json = "{ \"touser\":\"032043650|032043702\",\"agentid\":\"240153\",\"msgtype\":\"text\",\"text\":{ \"content\":\"" + TextBox1.Text+"\"} }";
        var httpContent = new StringContent(json, Encoding.UTF8);
        httpContent.Headers.ContentType = new MediaTypeHeaderValue("application/json");
        var response = client.PostAsync(url, httpContent).Result;
        Label1.Text = response.Content.ReadAsStringAsync().Result;
        return response.Content.ReadAsStringAsync().Result;




同样的字符，有时候报 [font='Microsoft YaHei', 'Helvetica Neue', Helvetica, Arial, sans-serif]post参数需要json类型。
[font='Microsoft YaHei', 'Helvetica Neue', Helvetica, Arial, sans-serif]