Brendan Enrick

Daily Software Development

Throwing Away Return Values

So it probably took me 15 seconds to track down this error in my code, and those wasted seconds, while very minor, are exactly why I wish Visual Studio or ReSharper or some program would alert me to what I've mistakenly done. It is easy with some methods to throw away a return value without noticing.

If I am calling a method which has a return value I am ignoring, it might be nice if it made it a little more obvious I am doing so. Perhaps an underline with a note explaining that I am not processing a return value. Sure lots of people ignore return values all the time, but they really shouldn't be. The return value probably exists for a reason.

As an example assume you want to get a substring.

string myString = "LongStringWithTooMuchStuffSoItProbablyNeedsToBeCutDownToSize";
myString.Substring(5,10);
Console.WriteLine(myString);

Looking at that code it is pretty easy to miss the fact that I am not doing anything with the return value. Right now the value written to the console is "LongStringWithTooMuchStuffSoItProbablyNeedsToBeCutDownToSize". I am just ignoring the value that substring is returning. This means I am not actually doing anything. I am just printing out the original string. What I really should have written is this.

string myString = "LongStringWithTooMuchStuffSoItProbablyNeedsToBeCutDownToSize";
myString = myString.Substring(5,10);
Console.WriteLine(myString);

It wouldn't be that difficult for a program to detect unused return values. I am already informed when I don't use variables. Since plenty of plug-ins for visual studio already read method signatures, one of them could easily detect that I am ignoring the return value of that method. Ah the little things. Not too big a deal, but kind of annoying since I executed my program once and had to look to see why my code didn't work as expected.

Maybe some program does mention this already, or maybe there is some setting I need to enable to do this. Please let me know if you know of one.

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