public class JsonpResult : JsonResult

    {

        public JsonpResult()

        {

            this.Callback = "callback";

        }

        public JsonpResult(string callback)

        {

            this.Callback = callback;

        }

        /// <summary>

        /// Jsonp 回调的 function 名称，默认为 callback

        /// </summary>

        public string Callback { get; set; }

        public override void ExecuteResult(ControllerContext context)

        {

            if (context == null)

            {

                throw new ArgumentNullException("context");

            }

            var request = context.HttpContext.Request;

            var response = context.HttpContext.Response;

            string jsoncallback = (context.RouteData.Values[this.Callback] as string) ?? request[this.Callback];

            if (!string.IsNullOrEmpty(jsoncallback))

            {

                if (string.IsNullOrEmpty(base.ContentType))

                {

                    base.ContentType = "application/x-javascript";

                }

                response.Write(string.Format("{0}(", jsoncallback));

                response.Headers.Add("P3P", "CP=CAO PSA OUR");

            }

            base.ExecuteResult(context);

            if (!string.IsNullOrEmpty(jsoncallback))

            {

                response.Write(")");

            }

        }

    }

 [HttpGet]

        public JsonpResult GetComContent( string key)

        {

            string data = "hi:"+key;

            return new JsonpResult() { Data = data, JsonRequestBehavior = JsonRequestBehavior.AllowGet };

        }