When User Clicks Dropdown / Doesn't Select Anything

I currently have a few comboboxes in my project that on the 'Dropdown' event, I have them show items from a database that I have bound to the Combobox, I have tried this on several other events too with the same result.The problem i'm having is when the user clicks the dropdown but doesn't select anything, it automatically defaults the first item in the combobox although nothing was ever really selected so what I want is the combobox to remain blank UNTIL they click on an item in the dropdown, is there a way to avoid this? Is there some code I can place in the combobox's selected indexchange to prevent the first item in the list from appearing unless it was actually physically clicked?