Index empty C#

how do I code exception if my Index is empty?
I meant if the index is empty and I want to notified the users that "There are no data in your selection" otherwise the code will pull data out.

currently my code is reading data from web service.  Following code are working only if there are data in the index
// for Auto Memos
string tempAutoMemos = response.MemosResults.ToList()[0].MemoText;
// for Visa Memos
string tempVisaMemos = response.MemosResults.ToList()[1].MemoText;

and my question is there is chance that response.MemosResults will be empty and I needed to code that exception so if response.MemosResults is empty or null then notify user with a message