COM and ASPX problem

[bluebytez]

Hi, I am trying to call a COM component from ASPX, but I keep getting an InvalidCastException, it seems that the QueryInterface for the object fails.
I wrote the dll in another machine and exported it using COM+ Services.
I've even tried to write a simple COM component which exposes only one public sub that does NOTHING, but the ASPX still can't seem to initialize the interface.
Can anyone shed any light on this ?

 

[link9]

You must create a wrapper for your classic COM object to use it w/in the .NET framework. Be warned that you will lose much of your performance when you do so. Unless it's just an enormous component, the best practice is to completely re-write it using a managed provider.

http://msdn.microsoft.com/library/en-us/vbcn7/html/vaconCOMInteroperability.asp?frame=true

http://www.aspzone.com/articles/john/dotNETInterop/

hope that helps!
paul

 

[link9]

ps -- to use the legacy component, you'll have to put this bit in your page directive:

aspCompat="True"

 

[chiph]

I agree with Link9 - you need to write a wrapper (VS.NET should do this for you when you set a reference to the COM object). But if the object is not huge, and especially if you're calling it alot, then you should re-write it as a managed component.

Another thing to think about is that VB6 components under COM+ are single-threaded, no matter what you set the options to. And another thing to think about is that COM+ objects that do database access automatically promote their isolation level to "serialized" (i.e. exclusive), thus locking everyone else out (even people just doing reads).

The more I hear about COM+, the less I like it. We've got a guy from Microsoft Premier Services in the office this week, and he's saying that MS itself is moving away from COM+.

Chip H.