Which thead executes an event handler ?

Using events is a common way to synchronize threaded applications. In this scenario, each thread raises an event to signal its status to the main program or other threads. Other parts of the application, outside the thread that raised the event, handle the event and process the information.

Note   When an event is raised from one object to another object, the event handler will execute on the same thread that the RaiseEvent occurred. Therefore, if the event handler accesses shared data it must itself use synchronization if that data may be simultaneously accessed on a different thread