> Ladies and Gents,
>
> I have an event that I raise.  When that event is raised I raise it like
> this:
>
> if (NewAlert == null) return;
>
> AlertEventArgs aea = new AlertEventArgs(EmployeeID, AlertID);
>
> EventHandler<AlertEventArgs> eh = null;
>
> foreach (Delegate del in NewAlert.GetInvocationList()) {
> try {
> eh = (EventHandler<AlertEventArgs>)del;
> eh(this, aea);
> } catch (Exception ex) {
> Console.WriteLine(ex.Message);
> NewAlert -= eh;
> }
> }
>
> The benefit is that I can remove any event handlers that aren't there
> anymore and it works like a dispatch so if the subscription is dead for
> whateve reason it's removed. Good stuff, I like it, makes everything faster
> because it's not trying dead events over and over again.
>
> The problem is that on the other side of the event when it's subscribed to,
> I can't figure out how to periodically check to see if I'm still subscribed
> to the event in the object.  I need to be able to do my += stuff and then
> later on a timer say "Is that += still hooked up?" and get a yes or no so
> that I can resubscribe just in case it was something bogus that happened
> that caused the event to be unsubscribed (like an unintended bug that causes
> the above code to fall into the catch)
>
> Does anyone know how to test if an event handler is still hooked up? I can't
> find any documentation on the subject.

"Larry Lard" <larryl***@hotmail.com> wrote in message
news:1145613373.031455.232740@i39g2000cwa.googlegroups.com...
>
> James Hancock wrote:
>> Ladies and Gents,
>>
>> I have an event that I raise.  When that event is raised I raise it like
>> this:
>>
>> if (NewAlert == null) return;
>>
>> AlertEventArgs aea = new AlertEventArgs(EmployeeID, AlertID);
>>
>> EventHandler<AlertEventArgs> eh = null;
>>
>> foreach (Delegate del in NewAlert.GetInvocationList()) {
>> try {
>> eh = (EventHandler<AlertEventArgs>)del;
>> eh(this, aea);
>> } catch (Exception ex) {
>> Console.WriteLine(ex.Message);
>> NewAlert -= eh;
>> }
>> }
>>
>> The benefit is that I can remove any event handlers that aren't there
>> anymore and it works like a dispatch so if the subscription is dead for
>> whateve reason it's removed. Good stuff, I like it, makes everything
>> faster
>> because it's not trying dead events over and over again.
>>
>> The problem is that on the other side of the event when it's subscribed
>> to,
>> I can't figure out how to periodically check to see if I'm still
>> subscribed
>> to the event in the object.  I need to be able to do my += stuff and then
>> later on a timer say "Is that += still hooked up?" and get a yes or no so
>> that I can resubscribe just in case it was something bogus that happened
>> that caused the event to be unsubscribed (like an unintended bug that
>> causes
>> the above code to fall into the catch)
>>
>> Does anyone know how to test if an event handler is still hooked up? I
>> can't
>> find any documentation on the subject.
>
> I suspect that there isn't any automatic way for doing this - because
> the information on how the event's invocation list is stored is a
> private implementation detail of the class containing the event. As far
> as clients are concerned, all they are allowed to do with
> <object>.NewAlert is:
>
> - add delegates
> - remove delegates
>
> To quote the spec:
>
>>>
> Since += and -= are the only operations that are permitted on an event
> outside the type that declares the event, external code can add and
> remove handlers for an event, but cannot in any other way obtain or
> modify the underlying list of event handlers.
>>>
>
> So I think you'd have to add a method to the class which enables
> clients to supply a delegate and ask, is this delegate hooked up to
> your NewAlert event? Then internally to the client, it would be OK to
> go through the the GetInvocationList and check:
>
>        public bool IsAttached(EventHandler eh)
>        {
>            if (TheEvent != null)
>            {
>                foreach (EventHandler itereh in
> TheEvent.GetInvocationList())
>                {
>                    if (itereh == eh)
>                        return true;
>                }
>            }
>
>            return false;
>        }
>
>
> --
> Larry Lard
> Replies to group please
>