public void ConfigureServices(IServiceCollection services)
{
services.AddMvc().AddJsonOptions(opt =>
{
opt.SerializerSettings.ContractResolver = new Newtonsoft.Json.Serialization.DefaultContractResolver();//json字符串大小写原样输出
});
}
.NET Core WebApi中返回 json 数据首字母大小写问题
原文：https://www.cnblogs.com/pingming/p/11330854.html