catch blocks that don't catch anything

Question

Is it good programming practice to make a catch block that does not catch anything? I mean something such as the folllowing:

catch(Exception ex) {}

The reason I ask is that there are some articles in this web site that do that. Is it good to show that as samples of good programming?

Sam Hobbs · Answer

Yes developers often don't take care of exceptions as thoroughly as we should especially in projects that are for learning purposes. Equivalently I sometimes leave out obvious exceptions to what I say. Certainly there are situations in which it is appropriate to ignore all errors and I apologize for not stating that explicitly.

theLizard · Answer

There are certain circumstances where catch(Exception ex) {} is used to simply fall through gracefully without crashing the system I know of cases (can't remember which ones though) where even if you had a message box or other error handling in the catch block it would never get there even though an error had been thrown because of say the return values from the place where the error occurred where not conducive to the type of error you are trying to catch Exception ex is a general catch condition and would not demonstrate what I am talking about but I assure you that what I am saying does happen. In these cases a general exception that does nothing is the only way to handle those types of errors. Frogleg's example is not a really good one because I would never see myself doing that in a try catch block no need to I would simply do this using (StreamReader sr = new StreamReader(@text.txt)) { string line; while ((line = sr.ReadLine()) != null && line.IndexOf() > 0) { string[] str = line.Split(''); // do whatever } } I do things like bool success = false; try { if(blah blah == getFromDatabase(harry potter)) success = true; } catch(Exceptionex) { //db error may have occurred don't care } return(success) in this case if there is a database error which I am really not interested in the catch stops an unconditional crash and the return value allows me to handle what I need to do. Bottom line is not all try catches need to handle exceptions with messages to the user.

Vulpes · Answer

Sorry I wasn't trying to imply that you're excused from writing poor code just because you're not a native English speaker! What I was implying is that the grammar of a native speaker of any language is likely to be better than that of a non-native speaker though this of course will certainly not be universally true.

Sam Hobbs · Answer

I would not be editing Hindi and this is not a matter of a human communication language. Let me emphasize this. It is frustrating for me when people post code of their own with catch blocks such as that.

Vulpes · Answer

I must confess that I often ignore error handling altogether when I post code partly through lack of time and partly because it may obscure whatever it is I'm trying to illustrate. In Frogleg's example I'd probably have used Trim() and/or the overload of String.Split() which ignores empty entries rather than try/catch but it's a good example nonetheless. I am full of admiration for authors who can write readable articles in something other than their native language. If Frogleg and I had to write our articles in (let's say) Hindi then I'm sure that Sam's red pencil would see a lot more action ;)

Mahesh Chand · Answer

I think it is OK to show this in your sample code because you're not really talking about a try..catch block but in real world application the catch block should catch something ;).

Sam Hobbs · Answer

Yes Vulpes my subject is incorrect. It is catching everything but just not doing anything. And I understand that articles are samples in articles are usually samples of other things. I hope that we can get articles to do something more like what Frogleg suggests. I don't want to name a specific article but there is one I looked at that is failing for some reason. I did not look closely but it is reading a web page as a text file and processing the HTML as text. It is apparently encountering an error and just quits without an error message or anything. So it is likely something such as what Frogleg shows. I see people posting code in forums with catch blocks as I describe. If people have problems with code samples from articles in this web site and they post questions here in forums about the code and the problem is hidden by this type of catch block then I think it would be better for sample code to show some kind of an error when relevant. If it is those of us in the forums that have to help with problems such as that then ir is relevant for us to ask that the problem be minimized. I think I see code such as that more than most members because I edit articles. Fortunately the two of you are so good at English grammar that I can ignore your articles but I ususally read them anyway because they are so good. I realize that there is not much we can do about code such as I describe here but I wanted to say something anyway.

Frogleg · Answer

Would you want to catch an exception and inform the user in this case try { using (StreamReader sr = new StreamReader(test.txt)) { string line; while ((line = sr.ReadLine()) != null) { string[] str = line.Split(''); // do whatever } } } catch (Exception ex) { //MessageBox.Show(ex.ToString()); } where for some reason there was a space between or especially at the end of the text file - (you don't need the spaces) or do catch the exception quietly and continue on

Vulpes · Answer

Well it's catching something - namely any exception which derives from the System.Exception class - but then choosing not to do anything about it. In practice I don't think there would be many occasions where you'd want to do this because if something is wrong and you're ignoring it then it may surface again later in the program. Often code within articles is just trying to illustrate some greater point so I think writers can be excused for not worrying too much about peripheral details.