如何在mvc4中使用filecontentresult时显示加载消息和错误消息？

Im generating a large csv file on the server and returning it in mvc4, this takes about 30 seconds. I want to show a loading message to the user but since I cant download files using ajax I dont know what I should do. also if the file cant be generated, i.e there was no relevant data to be used to generate the file I want to be able to return a message to appear in the same page , I dont want to refresh the page or return an error code. is this possible?Im generating a large csv file on the server an