Dynamically growing list

Question

Hi all, Im working on an assignment where I have to create a list of things. I use a radiobutton to see the list and another to create the list. the instruction was to make sure tht as I add into the list it grows...but the catch is that wen I load it again it shouldnt store the prev items. Shud erase them and reload them with the new item tht was currently added. So I cant use files or things like that. I thot of Arraylist/List but I dont knw if it an "recall" its prev items. Any ideas?
I am coding in c#
Thanks