How implement VB.NET interface event in managed c++?

  • Thread starter Thread starter Brett Hall
  • Start date Start date
B

Brett Hall

I have a VB.NET interface that my managed C++ code is to implement. I
seem to
be stuck implementing an event defined in that interface. Does anyone
have a
simple code snippet that will show me the basics of what I need to
implement?
I've seen all the MSDN articles on implementing events in managed C++
and
I've gotten events to work without issue when implementing all the
constructs
myself. I fail miserably when trying to correctly implement an event
defined
in a VB.NET interface. It's not clear what's defined implicitly and
explicitly. I need your help.

Let's say we have a trivial VB.NET interface defined (my syntax may be
off):

Public Interface ISomethingTrivial
Sub Func1()
Event Loaded()
End Interface

On the managed C++ side I would have:

__gc class MySomethingTrivial : public ISomethingTrivial
{
public:
// Constructor
// Destructor

void Func1() { /* Do something here */ }

// How implement the event here???
}

If I go ahead and implement the add_EventName() remove_EventName()
events I
get errors about multiple methods being defined. So I get the gist that
these
are created "behind the scenes" for me at compile time. I don't know
how to
define the raise_EventName() appropriately as I don't know what else is
under
the covers that I need to call. Each time I attempt to implement the
event
(incorrectly) I can successfully compile my managed C++ class, but when
I go
to instantiate an instance of it in my VB code I get "Cannot call New
on a
class listed as MustOverride". I assume I will see this until I
correctly
implement the event. Someone out there must have experience with
this....

Many thanks for your help. - Brett
 
Let's say we have a trivial VB.NET interface defined (my syntax may be
off):

Public Interface ISomethingTrivial
Sub Func1()
Event Loaded()
End Interface

On the managed C++ side I would have:

__gc class MySomethingTrivial : public ISomethingTrivial
{
public:
// Constructor
// Destructor

void Func1() { /* Do something here */ }

// How implement the event here???
}
Click to expand...


Did you try
__event void Loaded() { ... }
 
Thanks for the reply.

What do I call in { ... } to ensure clients that subscribed to the
event get the event? That's what I don't get. What do I call Invoke()
on to ensure subscribers of the event get the event? Is there a
delegate defined "under the covers" for me? This is where I'm lost.
Asking the question another way, is there a way to view my precompiled
header or class or whatever with the "under the covers" stuff shown?
Let me know if I'm still not making sense...
 
After some more experimenting tonight I have the answer for the example
above.

__gc class MySomethingTrivial : public ISomethingTrivial
{
public:
// Constructor
// Destructor

void Func1()
{
// Do stuff
Fire_Loaded();
}

virtual __event LoadedEventHandler *Loaded;
void Fire_Loaded()
{
Loaded();
}
};

Many Thanks. Brett
 
Back
Top