How to add morethan one interface for a COM object

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Hi,

I have created a COM DLL Server Project and accessed it by creating a clinet having CoCreateInstance().

Then i have modified the COM server project by adding one more interface.

In order to obtain the object for the second interface, i have called the QueryInterface function.

But QueryInterface always returns "E_NOINTERFACE".

What is the mistake i am making, please clarify.

What are the points we need to keep in mind while creating the second interface?

Kindly Advise.

Thanks,
Ganesamoorthy

Posted 27-Jan-11 19:38pm

Ganesamoorthy.S

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Sergey Alexandrovich Kryukov 28-Jan-11 1:42am

Show you code.

Ganesamoorthy.S 28-Jan-11 2:20am

<pre>HRESULT hr;
IGreet *greetObject;
IGreet2 *greetObject2;
CString strTemp;
hr = CoInitialize(NULL);
if (FAILED(hr) )
return ;
hr = CoCreateInstance(CLSID_Greet,NULL,CLSCTX_INPROC_SERVER, IID_IGreet,(void **)&greetObject);
if (FAILED(hr) )
{
CoUninitialize();
return ;
}
cout << greetObject->Sayhello("Ganesh") << endl;

hr = greetObject->QueryInterface(IID_IGreet2,(void **)&greetObject2);
if (FAILED(hr) )
{
CoUninitialize();
return ;
} </pre>

Ganesamoorthy.S 28-Jan-11 7:00am

AcceptÂ Answer RejectÂ Answer
.I have completed this on my own.

Adding interface to a COM, is as usual but if we suppose to use QUERYINTERFACE then it has to be implemented(implement interface option must be chosen).

I did it and got the expected result.

Sergey Alexandrovich Kryukov 28-Jan-11 12:04pm

What a relief! Thank you for the note. :-)
--SA

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Ganesamoorthy.S · Answer 1 · 2011-01-28T00:59:00

Solution 1

I have completed this on my own.

Adding interface to a COM, is as usual but if we suppose to use QUERYINTERFACE then it has to be implemented.

I did it and got the expected result.

Posted 28-Jan-11 0:59am

Ganesamoorthy.S

Debojyoti Majumder · Answer 2 · 2011-01-28T02:17:00

Solution 2

Have you updated the .idl file?
If not then update it.

Use the midl tool to compile your .idl file.
Add the changed files (stub and client) in your project.

Then use your COM object.
Hope this have helped you. ;P

Posted 28-Jan-11 2:17am

Debojyoti Majumder