public async Task <ActionResult> NewCoursesAsync()
{
var lastUpdateId = await CatalogManager.GetLastSuccessUpdateIdWithNewCoursesAsync();
var feedString = await CatalogManager.CreateUpdateFeedStringAsync(lastUpdateId, Request.Url, Url);
Response.Cache.SetExpires(DateTime.UtcNow.AddHours(24.0));
Response.Cache.SetCacheability(HttpCacheability.Server);
Response.Cache.AddValidationCallback(CheckCacheItem, lastUpdateId);
return(Content(feedString, "text/xml;charset=utf-8", Encoding.UTF8));
}