//返回json  大小写 配置
            services.AddMvc()
                    .AddJsonOptions( op => op.SerializerSettings.ContractResolver = 
                                           new Newtonsoft.Json.Serialization.DefaultContractResolver() );

//返回json 时间格式

.AddJsonOptions(op => op.SerializerSettings.DateFormatString = "yyyy-MM-dd HH:mm:ss");