1.需要引入包Microsoft.AspNetCore.Mvc.NewtonsoftJson
2.在StartUp.cs的ConfigureServices方法中进行注册

	services.AddControllers().AddNewtonsoftJson(options =>{options.SerializerSettings.ContractResolver = new DefaultContractResolver();});
3.前端ajax使用
$.ajax({url: ”“,type: "post",contentType: "application/json;charset=UTF-8",data: JSON.stringify({……}),success: function (data) {……},error: function (err) {……}});