What is the correct way to handle an unknown topic in a RTD server written in C++?

Asked Mar 18 '13 at 20:33

Active Mar 18 '13 at 20:33

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I'm writing an RTD server for Excel in C++. I've implemented my server and for the most part it works. The issue I have is when a cell has a call to RTD with a topic which isn't valid. For instance, I might have a call which looks like: =RTD("MyRTDServer", "", "realtime", A1, "IOPerSec")

Where the cell A1 will eventually have the name of a performance counter. When ConnecteData is called the first time, the topic might not be blank or invalid, but at some point later on, the topic changes because the content of A1 changes. I assume I will get another ConnectData call.

The questions I have is:

Can you do something in ConnectData to tell Excel that the topic is not valid?
If you can't tell Excel that the topic is not valid, how do you return N/A to Excel?

asked Mar 18 '13 at 20:33

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What happens if you return null from ConnectData? – Govert Mar 18 '13 at 20:52
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To return #N/A I think you need to create an error variant with code -2146826246. – Govert Mar 18 '13 at 21:00

What is the correct way to handle an unknown topic in a RTD server written in C++?

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