How can I pass structure pointer from COM server to .net client?

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Hi All,

I am a beginner in COM & .net interoperability.
I am having COM server dll which I am using into .net client through RCW(Runtime Callable Wrapper).
I have defined one custom structure in COM server application which I want to pass to .net client.
How can I expose this structure and is there any means to pass its pointer to client?
I tried using VARIANT* but this gives me exception as follows:
"An unhandled exception of type 'System.NullReferenceException' occurred in COMClient.exe
Additional information: Object reference not set to an instance of an object."

Is it a problem related to STA and MTA?

Please help me in this...

Thanks in Advance.

Posted 31-May-11 18:14pm

ggupta2009

Updated 31-May-11 18:41pm

Ramalinga Koushik

v2

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ggupta2009 14-Jul-11 1:02am

Thank you very much barneyman.

I got a good idea from your solution.

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barneyman · Accepted Answer · 2011-05-31T22:37:00

you can't pass ptr's between com and .net - one's memory is not addressable in the other

What you'll have to do is send a copy of the data over, and then marshal into .net

have a look at the size_is idl attibute on the com side

There's a good article here C# ATLCOM Interop code snipperts - Part 1[^]