C# 反序列化JSON

try
        {
            u = await WebAPIOperator.PostAsync("/v2.0/auth/user/user/login", new LoginRequestModel() { loginName = Name, password = Password , platformType = platformType });
        }
        catch (Exception ex)
        {
            LoginInfo.text = "登录服务器超时！";
            Log4NetHelper.Warning("系统登录超时\n" + "接口：/login?\n" + "返回值：" + (u != null ? u.ToString() : ""), ex);
            return;
        }
        LoginResponseModel lrm = JsonConvert.DeserializeObject<LoginResponseModel>(u);