September 2001
Intermediate to advanced
384 pages
11h 59m
English
Content preview from COM & .NET Component ServicesBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
Designing Queued Component Interfaces
When a client makes calls to a queued component, it interacts with the recorder provided by COM+. No actual calls to the real object occur. So, at the time of the call, the client has no way to receive output from the method, nor can it tell whether the call succeeded or failed. Consequently, when you design an interface to be supported by a COM+ queued component, you must avoid any outgoing parameters on any interface method.
Specifically, do not use any [out],
[in,out], or [retval] IDL
attributes on your method parameters. When you import a component
into the Component Services Explorer, COM+ inspects
the interfaces supported by that component, and if it detects an
output attribute, COM+ disables the queuing option for that
interface.
If you develop your COM+ component using Visual Basic 6.0, you do not
have direct access to your component IDL. Normally, this lack of
access would not be a problem. However, Visual Basic, by default,
treats method parameters as [in,out] parameters.
If you expect your component to be accessed as a queued component,
you have to explicitly use the Visual Basic ByVal
attribute on your method parameters.
Tip
In the next version of Visual Basic, Visual Basic.NET, all parameters are, by default, passed in by value instead of by reference. See Chapter 10 for more information.
A different kind of a parameter returned from a method is its return
value. You should avoid using custom
HRESULT
codes to indicate particular ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.