List Getting Cleared Every Button Click Inside Update Panel?

url...I've got a drop down inside an update panel, and I am trying to get it to allow the person using the page to add users to a list that is bound to a gridview. The list is a global variable, and on page_load I set that to the gridview's datasource and databind it. However, anytime I click the 'add a user' button, or the button to remove the user from the list. It appears like it is doing a full post back even though all these elements are inside the update Panel.[code]Now I thought the point of an update panel was to be able to update things inside of it without doing a full post_back and reloading the page. So if that's the case, why is it calling page_load everytime I click the buttons? I ran this code and debug and I see that even before any of the code associated with button press fires, page_load runs again.I tried putting the gvAssociatedUser.Datasource = associatedFaculty and the line below inside the Page.IsPostBack check, that prevented the page from working. I tried every combination of settings of the update panel for ChildrenAsTriggers and UpdateMode, and none of them worked.

I've tried won't get it to work.It wasn't causing a full postback so I was wrong as to the cause. I thought the page was doing a full post back thus resetting my associatedFaculty list global variable, but it isn't doing a full postback.The issue I am having is everytime I click btnAddUser it will add one element to the associatedFaculty list and thus bound to gvAssociatedusers. This works the first time, but the second time I click it, it overwrites the first element. So it appears like my associated Faculty list is getting reset each time I click the button?