MenuStrip.Items.Remove - Add Item To Dropdown Menu Upon Creation

I have my program set up to read the contents of a Directory, and then populate a drop down menu with the names of the files in the directory. (I am using the MenuStrip). Inside my program, it is also set up to create a new file in that directory, and I wish to add this item to the dropdown menu upon creation. The list is entirely created and populated from the code, and the contents of the list depend entirely on what's in the directory.

I have tried using MenuStrip.Items.Remove(menuItem1). Now, when this command gets executed, it does remove the top level Menu, however when I go to repopulate the menu, I end up with duplicates of my files listed in the drop down. I am stuck with how to clear these out as well?