If two delegates are created that point to the exact same method, and an
event is assigned both delegates, ...
myObj.MyEvent += new EventHandler(My Handler);
myObj.MyEvent += new EventHandler(My Handler);
.... does it recognize the duplicate method and ignore the second one, or
does it execute the same method twice when raised?
Jon
4  2525 
You'll delegate called twice.
Regards
Lee
"Jon Davis" <jo*@REMOVE.ME. PLEASE.jondavis .net> wrote in message
news:uD******** ******@TK2MSFTN GP10.phx.gbl... If two delegates are created that point to the exact same method, and an
event is assigned both delegates, ...
myObj.MyEvent += new EventHandler(My Handler);
myObj.MyEvent += new EventHandler(My Handler);
... does it recognize the duplicate method and ignore the second one, or
does it execute the same method twice when raised?
Jon
Jon,
Just a side note, this is very easy to test...
--
- Nicholas Paldino [.NET/C# MVP]
- ni************* *@exisconsultin g.com
"Jon Davis" <jo*@REMOVE.ME. PLEASE.jondavis .net> wrote in message
news:uD******** ******@TK2MSFTN GP10.phx.gbl... If two delegates are created that point to the exact same method, and an
event is assigned both delegates, ...
myObj.MyEvent += new EventHandler(My Handler);
myObj.MyEvent += new EventHandler(My Handler);
... does it recognize the duplicate method and ignore the second one, or
does it execute the same method twice when raised?
Jon
Even easier to ask. ;)
Jon
"Nicholas Paldino [.NET/C# MVP]" <ni************ **@exisconsulti ng.com> wrote
in message news:u5******** ******@TK2MSFTN GP10.phx.gbl... Jon,
Just a side note, this is very easy to test...
--
- Nicholas Paldino [.NET/C# MVP]
- ni************* *@exisconsultin g.com
"Jon Davis" <jo*@REMOVE.ME. PLEASE.jondavis .net> wrote in message
news:uD******** ******@TK2MSFTN GP10.phx.gbl... If two delegates are created that point to the exact same method, and an
event is assigned both delegates, ...
myObj.MyEvent += new EventHandler(My Handler);
myObj.MyEvent += new EventHandler(My Handler);
... does it recognize the duplicate method and ignore the second one, or
does it execute the same method twice when raised?
Jon
>> You can check whether a delegate contains a given event handler by
iterating
over the return value of GetInvocationLi st and using the overridden equality
operator (==) to check. <<
This is an excellent and very relevant answer, Simon, thank you very much!
Jon
"Simon Trew" <ten.egnaro@wer ts> wrote in message
news:ux******** ******@TK2MSFTN GP11.phx.gbl... The Remarks section of http://tinyurl.com/hsmt (MSDN Delegate.Combin e
documentation) states:
"The invocation list can contain duplicate entries; that is, entries that
refer to the same method on the same object."
The "Return value" section of http://tinyurl.com/hsne (MSDN
Delegate.Remove documentation) states:
If the invocation list of value matches a contiguous set of elements in
the invocation list of source, then the invocation list of value is said to
occur within the invocation list of source. If the invocation list of
value occurs more than once in the invocation list of source, the last
occurrence is removed.
So also, you will need to remove (using -= in C#) the same number of
duplicates as you added.
You can check whether a delegate contains a given event handler by
iterating over the return value of GetInvocationLi st and using the overridden
equality operator (==) to check.
e.g.
bool DelegateContain sHandler(Delega te delegate, EventHandler handler)
{
bool bFound = false;
foreach (Delegate d in MyObj.MyEvent.G etInvocationLis t())
{
bFound = d == handler;
if (bFound) break;
}
return bFound;
}
"Jon Davis" <jo*@REMOVE.ME. PLEASE.jondavis .net> wrote in message
news:uD******** ******@TK2MSFTN GP10.phx.gbl... If two delegates are created that point to the exact same method, and an
event is assigned both delegates, ...
myObj.MyEvent += new EventHandler(My Handler);
myObj.MyEvent += new EventHandler(My Handler);
... does it recognize the duplicate method and ignore the second one, or
does it execute the same method twice when raised?
Jon
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