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vbcomponents thread: mts events


Message #1 by Shreekar Joshi <joshishreekar@y...> on Mon, 4 Mar 2002 23:35:19 -0800 (PST)
For COM+ Events, you can read the "Platform SDK Documentation\Component 
Services\Com+ (Component Services)\Services Provided by COM+\COM+ Events" 
subject in MSDN.  If you feel a little boring to find the document in such 
deep path, you can just search & open the cossdk.chm file after you 
installed MSDN with "Platform SDK Documentation" option selected.
Reading the topic can make you know all about the new features in COM+ 
(relate to COM), then you will will agree that COM+ > mts + com + msmq.
If you think reading this topic will cost you many many time, here is the 
shorter version in my mind:
For events defined in COM, we need to declare it with "dim withevents" 
statment, this will limited to early binding programs & just cause 
broadcast for all processes bind to this event (in same computer).
So once event fired, it needs to wait all processes that already bind to 
it to finish their response functions one by one, then it can continue the 
next statment below the statmant that fire this event.
For COM+ Events, MS bring new concept for event binding.  It will be 
defined as following simple example:
1. make one public creatable ComA with Method1 (can be no any statment in 
this method), and this method has some parameters.
2. In ComB, define Method2, create one instance of ComA & call Method1 
with information as parameters that need to be transfered to other 
processes just like in event.
3. In ComC, define Methon3, implements ComA & write the code in Method1 to 
deal with the parameters (maybe just simply display them in the form).
4. In COM+ Application, add ComB & ComC, create one event publisher EP1 
for ComB, create one event subscription ES1 for EP1.
Then every time, while ComB call the ComA.Method1, the implemented code in 
ComC will be called.
You can just imagine that through COM+ Events stratage, we just link the 
ComB.Method2 & ComC.Method3 together, once Method2 be called, Method3 will 
be called too.
Because we are not using events here, so only ComC will be response to 
the "Method2 event".
With using more features in COM+ Events, we can use transience com+ event 
binding & event filter to let not all instance of ComC to be called.  And 
all ComC can also be defined to be called pararell too.
And with QC, we even can let this calling be tranfered to other 
computers...
Use COM+ features wisely, you will find it is powerful than mts + com + 
msmq (sure, .net will be much better).

Wish this could let you have an idea about COM+ Events.  

Kent Liu
MCSD

> Hi
> 
> Thanks a lot for the reply.
> I admit it is a bit daunting for me right now to
> understand what u r saying.
> Can u please shed some light on what is the Event
> Subscription ? 
> Meanwhile, I will dig deeper into MSDN to understand
> what u r saying.
> With help, I am determined to make this work.
> 
> Regards
> Shreekar Joshi

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