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PO
 

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    <p>Exceptions were designed for exactly that - exceptional circumstances. I try and think of it like this - if you assume everything that you depend on is working as normal for the majority of the time, and method X fails, then it's an exceptional circumstance because it doesn't normally happen and you should define exceptions to catch the situation.</p> <p>So in your situation, you assume the device to be up and running. Therefore exceptional circumstances in this case are the device not accepting a connection, it rejecting a connection, it not accepting data you send it or you not receiving data it should be sending etc. If your devices are routinely turned off several times a day, then you expect them to be turned off, so use return codes or a "bool IsDeviceOn();" method to check it before you connect.</p> <p>If it's something that you <strong>do expect</strong> to happen in normal circumstances, such as querying a device for its capabilities but the one you want isn't available, then use return codes, or a bool method - e.g. "bool DoesDeviceHaveThisCapability();" Don't catch an exception when it doesn't.</p> <p>Another example (for GUI apps) is user input. Don't use exceptions for that, because you do expect a user to input something incorrectly - we're not perfect.</p> <p>I have experienced massive performance issues due to using exceptions when they weren't truly exceptional circumstances. One example was when I was processing a 2GB data file 2-3 times a day. Some lines had valid prices in the format 0.00. Some didn't. I used a FormatException to catch those that didn't.</p> <p>Two years later when I had the chance to get a performance analyser on it, that particular line that caught the exception was responsible for 80% of the time used to analyse the file. I changed that to use the TryParse() method of int instead, and got a massive speed increase.</p> <p>For your examples, I would probably use:</p> <ol> <li>No response from device - exception if devices should be on 24/7, return code if routinely powered off</li> <li>Operation unauthorised - exception</li> <li>Comms failed - exception</li> </ol>
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    1. POConfused about when to throw an exception
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    1. USAndy Shellam
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    1. COI ended up doing pretty much exactly as u suggested. Thanks.
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      1. USHemant
 

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