Json.Net

    public class JsonNetResult : JsonResult
    {
        public JsonSerializerSettings Settings { get; private set; }
        public JsonNetResult()
        {
            Settings = new JsonSerializerSettings
            {
                //忽略循环引用，如果设置   //为Error，则遇到循环引用的时候报错（建议设置为Error，这样更规范）
                ReferenceLoopHandling = ReferenceLoopHandling.Ignore,
                //日期格式化，默认的格式也不好看                      
                DateFormatString = "yyyy-MM-dd HH:mm:ss",
                //json中属性开头字母小  写的驼峰命名
                ContractResolver = new CamelCasePropertyNamesContractResolver()
            };
        }

        public override void ExecuteResult(ControllerContext context)
        {
            if (context == null)
                throw new ArgumentNullException("context");

            if (JsonRequestBehavior == JsonRequestBehavior.DenyGet && string.Equals(context.HttpContext.Request.HttpMethod, "GET", StringComparison.OrdinalIgnoreCase))
                throw new InvalidOperationException("JSON GET is not allowed");

            HttpResponseBase response = context.HttpContext.Response;
            response.ContentType = string.IsNullOrEmpty(this.ContentType) ? "application/json" : this.ContentType;

            if (this.ContentEncoding != null)
                response.ContentEncoding = this.ContentEncoding;

            if (this.Data == null)
                return;

            var scriptSerializer = JsonSerializer.Create(this.Settings);
            scriptSerializer.Serialize(response.Output, this.Data);
        }
    }

    public class JsonNetActionFilter : IActionFilter
    {
        public void OnActionExecuted(ActionExecutedContext filterContext)
        {
            //把 filterContext.Result从JsonResult换成JsonNetResult
            //filterContext.Result值得就是Action执行返回的ActionResult对象
            if (filterContext.Result is JsonResult && !(filterContext.Result is JsonNetResult))
            {
                JsonResult jsonResult = (JsonResult)filterContext.Result;
                JsonNetResult jsonNetResult = new JsonNetResult();
                jsonNetResult.ContentEncoding = jsonResult.ContentEncoding;
                jsonNetResult.ContentType = jsonResult.ContentType;
                jsonNetResult.Data = jsonResult.Data;
                jsonNetResult.JsonRequestBehavior = jsonResult.JsonRequestBehavior;
                jsonNetResult.MaxJsonLength = jsonResult.MaxJsonLength;
                jsonNetResult.RecursionLimit = jsonResult.RecursionLimit;
                filterContext.Result = jsonNetResult;
            }
        }
        public void OnActionExecuting(ActionExecutingContext filterContext)
        {
        }
    }