ASP.NET Core中返回 json 数据首字母大小写问题

// This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.Configure<CookiePolicyOptions>(options =>
            {
                // This lambda determines whether user consent for non-essential cookies is needed for a given request.
                options.CheckConsentNeeded = context => true;
                options.MinimumSameSitePolicy = SameSiteMode.None;
                
            });

            //options.SerializerSettings.ContractResolver = new Newtonsoft.Json.Serialization.DefaultContractResolver();//json字符串大小写原样输出
            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);
                //.AddJsonOptions(opt => { 
                //    opt.SerializerSettings.ContractResolver = new Newtonsoft.Json.Serialization.DefaultContractResolver();
                //    });// json字符串大小写原样输出


        }