Accessing COM error info from c#

[SimonHeffer]

I have a COM server written in MSVC 6 C++. If I use a C++ client and get an error my server will give back error information using IErrorInfo. So if the client calls a method that throws a com_error exception the following will find out what's gone wrong...

ReportErrorInfo(IUnknown * punk){
	USES_CONVERSION;
	CComBSTR bstrError;
	CComPtr<ISupportErrorInfo> pSEI;
	if (!punk)
	{
		strcpy(ErrorMessage,"No interface to COM server");
	}
	else try
	{
		HRESULT hr = punk->QueryInterface(IID_ISupportErrorInfo,(void **) &pSEI);
		if(SUCCEEDED(hr))
		{
			CComPtr<IErrorInfo> pEO;
			if(S_OK == ::GetErrorInfo(NULL, &pEO))
			{
				CComBSTR bstrDesc;
				pEO->GetDescription(&bstrDesc);
				strcpy(ErrorMessage,OLE2T(bstrDesc));
                               // something useful in ErrorMessage by now
...

But when calling the same method on the server (and expecting the same error) from a C# client using catch (COMException e) then e.Message is
"Error HRESULT E_FAIL has been returned from a call to a COM component."

rather than what GetDescription( ) returns.

Any idea where to start looking?

[Plater]

Well you could try looking to see if there is an inner exception
OR tell it to catch (Exception e) instead of a specific type.
Since I think if <some exceptiontype A> inherits from comException, then catching comException will catch that <some exceptiontype A> and cast it as a comException, losing info?
The same might also apply if the inner exception is comException and there's an out exception?
Not sure if that will help at all or not

[SimonHeffer]

Thanks for that.

However I've tried both with no luck.

[Plater]

You could try writing an unmanged wrapper for it that would take the correct com_error thing and fire off a managed-style error message?

Not that I know how to do that, just throwing it out there.