.NET called as COM interface

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Dave Braithwaite - 21 Jun 2005 18:41 GMT

I'm having trouble getting my head around calling .NET components from
legacy VC6.

I need to implement a logging "thing" (service, object, application,
whatever) in C# that will be called by legacy vc6 code. This "thing" will
need to:

- log messages from client applications to an SQL Server (MSDE) database
- minimise performance hit to client applications
- raise events after log messages are written to the database
- manage and limit connections to database given that its MSDE.
- support lots of potential simultaneuos connections from client
applications (say 20).

I believe I need to employ the COM interop services so that my client
applications can call into the .NET logging thing using COM.

I think I need to implement a global message queue. This will be serviced
by a thread that will pull log messages off one-by-one and add them to the
database raising events as it goes. I will also need some form of object(s)
that can be called by the client applications to place messages on this
queue.

I've had a look at c# objects exposed via CCW, COM+ and Window Services.
And am a little confused. Can someone, anyone, give me some pointers as to
how to proceed with all of this ?

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Nassos - 22 Jun 2005 13:53 GMT

Hi Dave,
Create a dll using c# and then use CreateObject from VB, you will not have
autoComplete, but this is a minor problem.
Hope that Helps

> I'm having trouble getting my head around calling .NET components from
> legacy VC6.
[quoted text clipped - 24 lines]
> to
> how to proceed with all of this ?

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dbraithwaite@lkuk.co.uk - 24 Jun 2005 08:34 GMT

Can you expand some please ?

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Nassos - 27 Jun 2005 09:11 GMT

Sure man , but bear with me cos my VB suck,
lets say that you build a Dll library with .NET called Test and contains 2
classes class1 and class 2 be carfull there is a option in vs.NET that allow
your dll to have com interoptability and produces a tlb file as well as a
dll, after you build your dll run cmd (Command prompt) and run regasm for
your tlb and dll, this will finish the NET part.
Now in the vb6 do:
Dim obj as Object
set obj = CreateObject("Test","Class1")
now this object obj has the methods and attributes of the Class1 class in
the Test dll, but if you type:
obj.Start() if the method Start exist, cos when you press the dot you will
NOT have a list of the available methods and attributes, it will run the
method and if doesn't exist it will NOT produce an error.
Hope that helps

> Can you expand some please ?

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Nassos - 27 Jun 2005 09:18 GMT

here is a microsoft link for making a NET dll and call it as COM
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dndotnet/html/c
allnetfrcom.asp
CU

> Sure man , but bear with me cos my VB suck,
> lets say that you build a Dll library with .NET called Test and contains 2
[quoted text clipped - 13 lines]
>>
>> Can you expand some please ?

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dbraithwaite@lkuk.co.uk - 28 Jun 2005 10:46 GMT

Thanks for the help.

In the end, I decided to ditch C# and go back to good old (unmanaged)
C++ as an ATL server. I've implemented pretty much all I specified in
the post.

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.NET called as COM interface

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