Forcing RegisterXLL function to return false

[Andrew Lockhart]

Hi,

I've created an XLL/COM addin project like the example in the distribution, ComAddInRegisterObject.dna, but using C#. I'm writing some error handling at start up and there are certain situations where the XLL/COM addin will not be able to load and run the code, but not initialise correctly, such as missing environment variables etc. - run-time errors in the COM Addin OnConnection Method. I have a VBA Addin that is calling RegisterXLL to start up my XLL/COM object.

RegisterXLL returns a Boolean; is there a way to programmatically set this return value? Auto_Open doesn't return a value and throwing an exception from Auto_Open causes the ExcelDNA diagnostics to come up. Ideally I would like my VBA code to try and load the add-in and be able to detect if there are any initialisation errors.

Or is the recommendation to hold a global in the C# that I query from a very simple XLL function called something like InitialisedOK?

Regards

[Govert van Drimmelen]

Hi Andrew,

 

Microsoft’s documentation for xlAutoOpen (the .xll entry point) states that:

“Your implementation of this function must return 1 (int).”

So it does not seem like an appropriate mechanism for indicating some error during loading.

There might be some other error cases that cause RegisterXLL to return something interesting, of course.

 

In Excel-DNA the plumbing around AutoOpen is not likely to change anyway, so I can’t see a good way to thread some result code back with this mechanism.

 

Your add-in specific mechanism with a simple XLL function (which you can make hidden so it doesn’t show up the functions dropdown) should be fine. It can even return a string with some diagnostic information if there is an error.

 

-Govert

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[Andrew Lockhart]

Thanks, that's exactly what I did and it worked fine.

Regards

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