Working with Event Handlers in .NET -

when adding handlers indiscriminately object's events, realized can attach same handler event many times like. means handler called once each time attached.

i'm wondering these things:

• is there way @ handlers have been added object's event?
• is possible remove handlers event?
• where these correlations between event , handler stored?

if event marked c# event keyword there's no way outside object see subscribers - requisite information not visible.

from inside, can done, though complex , relies on details of implementation might change (though, haven't yet).

a workaround might useful though, it's valid remove handler that's not there - no exception thrown.

so code valid:

myconnection.closing -= connectionclosinghandler; myconnection.closing += connectionclosinghandler; 

if you're subscribed event, first line removes subscription.
if you're not subscribed event, first line nothing.

the second line hooks new subscription, , you're guaranteed not notified multiple times.

to answer last bullet point, when declare normal event:

public event propertychangedeventhandler changed; 

the compiler creates member variable of type propertychangedeventhandler stores subscribers. can take on storage if want:

public event propertychangedeventhandler changed {      add { ... }     remove { ... } } 

the use of -= , += modify subscription isn't syntactic sugar - delegates immutable, , new instance returned when add or remove handler. have @ delegate , multicastdelegate (both msdn links) more information on how works.