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Visual Studio Bug – ‘if’ followed by a try / catch causes debugger stepping error

Yesterday I was debugging and stepped into a method. I wanted to get past my parameter validation checks and into the meat of the method, so I quickly, F10’d my way down the method, but I noticed a line of code was stepped on which should not have been touched. The code was a simple parameter validation like: 1 2 if (enumerableObj == null) throw new ArgumentNullException("enumerableObj"); with several similar parameter validation lines above it and a try/catch block containing the meat of the method below it. The odd thing was, I thought I saw the debugger step on the throw statement even though the enumerableObj should have had a value. I assumed I had somehow passed in a null value to the enumerableObj parameter and had nearly missed the problem in my haste. I had been moving quickly, so quickly in fact that I had stepped about 3 more lines into the method before I even stopped. To be honest at this point, I wasn’t even sure if I saw it step into the ‘if’ block, so I repositioned my debug cursor back to the ‘if’ condition, and stepped again. Sure enough, it stepped into the ‘if’ block. I assumed I passed in a null parameter, but when I evaluated enumerableObj, it was set, what’s more, evaluating the entire enumerableObj == null expression resulted in false, as expected. But why the heck was I being stepped into the ‘if’ block when the ‘if’ condition was false? I retried it again, just in case the enumerableObj had somehow been set as a result of a side effect somewhere, but even then, it still stepped into the ‘if’ block. So, I did the standard stuff; cleaned my solution, deleted my bin and obj directories, reopening the solution, restarted Visual Studio, & rebooted, all the while rebuilding and retesting the project with each change. Nothing seemed to work. I even cut & pasted my code into notepad, then cut & pasted from notepad back into Visual Studio to ensure there was no hidden characters in my files.* None of this worked, so I started commenting out code in the method, and eventually was able to isolate it to the above code failing if, and only if, it was followed by a try / catch block. Seriously! If the try / catch block was there, it would step onto the throw statement even though it should not have, but when you removed... read more

Hey #region haters; Why all the fuss?

I hear a lot of programmers saying #regions are a code smell. From programmers I don’t know to celebrity programmers, while the development community appears to be passionately split.* The haters definitely have a point about it being used to hide ugly code, but when I open a class and see this, it just looks elegant to me. Now none of these regions are hiding thousands of lines of ugly code, actually, most of these regions contain only 3 properties and/or methods and the last curly brace is on line 299. So the whole thing with 17 properties and methods including comments and whitespace is only 300 LOC. … really, how much of a mess could I possibly be hiding? To me, the only question is whether I should have this functionality in the ContainerPageBase or the MasterPageBase**. You may also notice the regions I have are not of the Fields / Constructors / Events / Properties / Methods variety. It has taken some time for me to accept that all data members (aka fields) do not need to be at the top of the class as I was classically trained to do and that perhaps grouping them by functionality is a better idea. This philosophy only makes regions that much more valuable. … is anybody still here? …. have I converted anyone? 😉 * These posts are fairly old, but in my experience in the developer community; the consensus hasn’t changed. ** The Database Connection & Current User regions may have some scratching their heads. There are valid reasons for them, however the Data Connection region will never be included at this level again. More on that in a future post. Copyright © John MacIntyre 2010, All rights... read more

Workaround: Visual Studio Debugger will not step.

Often while I’m stepping through server side code, I’ll get the error message “Unable to step. The operation could not be completed. A retry should be performed.” Or the “Unable to step. The message filter indicated that the application is busy.” message. Once you’ve gotten either of these messages, neither F10 or F11 will work, you just keep getting the same message. Finding information on this problem has been elusive, but I finally found this blog post which confirms the problem I’ve always suspected, that it’s a race condition in the VS debugger which is triggered by pressing either F10 or F5 at the same time as a javascript event is triggered in IE. The blog post outlines 3 workarounds, none of which I care for, so I thought I’d share a little trick I’ve discovered which will usually allow you to get back on track and start debugging again. Here’s how I get the debugger back on track: Place a break point on the next line of code Press F5 When the break point is hit, F10 & F11 will work again Warning: There have been a few times when the debugger did not stop on my breakpoint, but for the most part, it stopped 99% of the time. I may have missed a distinction in those few... read more

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