Casting Using Dynamic in c#

 [HttpPost]
        [CustomAuthorize(Roles = ACUserRoles.Admin + "," + ACUserRoles.ACRStaff)]
        public JsonResult AjaxGetACRStaff(Grid.GridFilter Filter)
        {
            dynamic s = JsonConvert.DeserializeObject(Filter.AddinfoJson);
            var releaseid = Convert.ToInt32(s["releaseid"]);
            var grid = GetACRStaff(Filter, null, releaseid);
            return Json(grid, JsonRequestBehavior.DenyGet);
        }