摘要：
services.AddMvc（）.AddJsonOptions（options=>；set；}publicoverridevoidOnActionExecuted（ActionExecutedContextactionExecutedCntext）｛varjsonResult=（JsonResult）actionExecutedTontext.Result；
.NetCore的Controller/WebAPI可以帮我们将返回结果自动转换为Json格式给前台，而且可以自由设定格式（大写、小写、首字母大写等），我总结了三种方法，对应三种灵活度，供大家参考
（一）通过Startup.cs设置项目级别的格式
在项目Startup.cs中增加如下配置：
services.AddMvc().AddJsonOptions(options => { options.SerializerSettings.ContractResolver = new DefaultContractResolver(); }); 默认为保持原样，也可设定为CamelCasePropertyNamesContractResolver()，即首字母小写的驼峰格式。
本身是没有将属性全部小写的方法，我这里提供一个参考，大家可以自定义想要的格式：
public class LowercaseContractResolver : Newtonsoft.Json.Serialization.DefaultContractResolver { protected override string ResolvePropertyName(string propertyName) { return propertyName.ToLower(); } }
（二）设置Controller/WebAPI级别的统一格式转换，这里用到了ActionFilterAttribute，扩展出一个CustomActionJsonFormatAttribute标签
public class CustomActionJsonFormatAttribute : ActionFilterAttribute { private Type _ContractResolver { get; set; } public CustomActionJsonFormatAttribute(Type ContractResolver) { _ContractResolver = ContractResolver; } public override void OnActionExecuted(ActionExecutedContext actionExecutedContext) {var jsonResult = (JsonResult)actionExecutedContext.Result; jsonResult.SerializerSettings = new JsonSerializerSettings { ContractResolver = Activator.CreateInstance(_ContractResolver) as IContractResolver }; actionExecutedContext.Result = jsonResult; } }
使用时在Controller/WebAPI中添加如下代码即可，即可以在class层面添加，也可以在Action上添加：
[CustomActionJsonFormat(typeof(LowercaseContractResolver))]
public IActionResult EntityInfo([Required]string entityid) { ... }
（三）在代码返回的时候设置JsonResult，这个是最灵活但也最麻烦的方式：
return new JsonResult(new Entity { EntityId = entityid, Name = entityType.Name, OrganizationId = Permission.getCurrentUserOrg().ORG_GID }, new JsonSerializerSettings { ContractResolver = new LowercaseContractResolver() });