Release Lock when form close

Question

Hi.

I have a form which have System.Threading.Timer which is updating after 1 sec.

In timer tick method i have a list on which i acquire lock first the extract data from list and display it in the Grid view.

problem is this when I close the form, application hangs sometime.

In form closing i am using following statement to close the timer

timerUpdate.Change(Timeout.Infinite, Timeout.Infinite);

Does it required to release lock from the list [which was locked in timer tick method]??