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COM & Errors

Posted on 1998-07-21
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Last Modified: 2013-11-25
I've got a COM server written in VC++ 5.0 with ATL whose target client is applications written in VB.  What I would love to do is throw an exception from the COM component and have standard error handling in VB be able to trap it.  This approach isn't working.  I'm having a hard time finding any documentation on this issue.  Please help.
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Question by:rayb
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eburley earned 50 total points
ID: 1168208
support the ISupportErrorInfo interface, implementing InterfaceSupportsErrorInfo(riid) (ATL has an ISupportErrorInfoImpl which does this for you)

when an error happens:
Call CreateErrorInfo, passing the address of an
 ICreateErrorInfo * as the argument.

you can then use the functions in the ICreateErrorInfo object (SetDescription, SetGUID, SetHelpContext, SetHelpFile, SetSource) to populate the error.

when vb sees the error in IDispatch, it will call GetErrorInfo, then call InterfaceSupportsErrorInfo.  if your interface returns S_OK from this, vb will assume the error is legit, and use the information in the error object to inform the user.
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by:rayb
ID: 1168209
Thanks

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