//Nuget引入 Microsoft.AspNetCore.Mvc.NewtonsoftJson
builder.Services.AddControllers().AddNewtonsoftJson(options => {
// 忽略循环引用
options.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
// 不使用驼峰
options.SerializerSettings.ContractResolver = new DefaultContractResolver();
// 设置时间格式
options.SerializerSettings.DateFormatString = "yyyy-MM-dd HH:mm:ss";
// 如字段为null值，该字段不会返回到前端
options.SerializerSettings.NullValueHandling = NullValueHandling.Ignore;
});