格式化日期,首字母大写

1.添加 

Install-Package Microsoft.AspNetCore.Mvc.NewtonsoftJson -Version 3.0.0-preview8.19405.7

2.格式化

services.AddRazorPages().AddNewtonsoftJson(options => {

options.SerializerSettings.DateFormatString = "yyyy-MM-dd HH:mm:ss";

options.SerializerSettings.ContractResolver = new DefaultContractResolver();

});