Question

I am trying to add and remove events from a timer and I have the following code:

Timer myTimer = new Timer(); // Windows.Forms Timer  public void addEvent(MyDelegate ev) {     myTimer.Tick += new EventHandler(ev); }  public void removeEvent(MyDelegate ev) {     myTimer.Tick -= new EventHandler(ev); } 

I don’t know If Im doing anything stupid in trying to add and remove delegates in this fashion, I am able to add delegates and get them to fire as expected. However, when I attempt to remove the events, they continue to fire on Timers Tick.

Can anyone see anything obviously wrong?

Answer 1

I believe that this code:

myTimer.Tick -= new EventHandler(ev); 

creates a new EventHandler object. It will never remove an existing EventHandler. To get the functionality you want, you should be passing in EventHandlers, not MyDelegates, to the add and remove methods:

Timer myTimer = new Timer(); // Windows.Forms Timer  public void addEvent(EventHandler ev) {     myTimer.Tick += ev; }  public void removeEvent(EventHandler ev) {     myTimer.Tick -= ev; } 

The calling code will have to keep track of the EventHandlers added, so that it can pass in the same EventHandler object when it is time to unsubscribe.