I've got a winforms application that is set up in the following manner: 2 buttons, a textbox, a collection K, function X and another function, Y.

1. Function X parses a large database and enumerates some of its data in the global collection.
2. Button 1 calls function X.
3. Function Y walks through the above collection and prints out the data in the textbox.
4. Button 2 calls function Y.

I'd like to call function X through a worker thread in such a way that:

1. The form remains responsive to user input. This comes intrinsically from the use of a separate thread.
2. There is never more than a single instance of function X running at any point in time.
3. K can be accessed by both functions at all times.

What would be the most efficient implementation of the above environment ?