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When Are You Required To Set Objects To Nothing?

  • Artigo

A quick follow up on my earlier entry on the semantics of Nothing in VBScript. I see code like this all the time:

Function FrobTheBlob()
Dim Frobber, Blob
Set Frobber = CreateObject("BitBucket.Frobnicator")
Set Blob = CreateObject("BitBucket.Blobnicator")
FrobTheBlob = Frobber.Frob(Blob)
Set Frobber = Nothing
Set Blob = Nothing
End Function

What's the deal with those last two assignments? Based on the number of times I've seen code that looks just like this, lots of people out there are labouring under the incorrect belief that you have to set objects to Nothing when you're done with them.

First off, let me be very clear: I'm going to criticize this programming practice, but that does NOT mean that you should change existing, working code that uses it! If it ain't broke, don't fix it.

The script engine will automatically clear those variables when they go out of scope, so clearing them the statement before they go out of scope seems to be pointless. It's not bad -- clearly the code works, which is the important thing -- but it needlessly clutters up the program with meaning-free statements. As I've ranted before, in a good program every statement has a meaning.

When I see code like this, the first thing I think is cargo cult programmer. Someone was told that the magic invocation that keeps the alligators away is to put a banana in your ear and then set objects to Nothing when you're done with them. They do, and hey, it works! No alligators!

Where the heck did this thing come from?; I mean, you don't see people running around setting strings to "" or integers back to zero. You never see it in JScript. You only ever see this pattern with objects in VB and VBScript.

A few possible explanations immediately come to mind.

Explanation #1: (Bogus) Perhaps some earlier version of VB required this. People would get into the habit out of necessity, and when it became no longer necessary, it's hard to break the habit. Many developers learn by reading old code, so those people would pick up on the old practice.

This explanation is bogus. To my knowledge there has never been any version of VB that required the user to explicitly deallocate all objects right before the variables holding them went out of scope. I'm aware that there are plenty of people on the Internet who will tell you that the reason they set their objects to Nothing is because the VB6 garbage collector is broken. I do not believe them. If you've got a repro that shows that the GC is broken, I'd love to see it.

Explanation #2: (Bogus) Circular references are not cleaned up by the VB6 garbage collector. You've got to write code to clean them up, and typically that is done by setting properties to Nothing before the objects go out of scope.

Suppose you find yourself in this unfortunate situation:

Sub BlorbTheGlorb()
Dim Blorb, Glorb
Set Blorb = CreateObject("BitBucket.Blorb")
Set Glorb = CreateObject("BitBucket.Glorb")
Set Blorb.Glorber = Glorb
Set Glorb.Blorber = Blorb
'
' Do more stuff here
'

and now when the procedure finishes up, those object references are going to leak because they are circular.

But you can't break the ref by cleaning up the variables, you have to clean up the properties. You have to say

Set Blorb.Glorber = Nothing
Set Glorb.Blorber = Nothing

and not

Set Blorb = Nothing
Set Glorb = Nothing

Perhaps the myth started when someone misunderstood "you have to set the properties to Nothing" and took it to mean "variables" instead. Then, as in my first explanation, the misinformation spread through copying code without fully understanding it.

I have a hard time believing this explanation either. Because they are error-prone, most people avoid circular references altogether. Could it really be that enough people ran into circular ref problems and they all solved the problem incorrectly to cause a critical mass? As Tommy says on Car Talk: Booooooooooooogus!

Explanation #3: It's a good idea to throw away expensive resources early. Perhaps people overgeneralized this rule? Consider this routine:

Sub FrobTheFile()
Dim Frobber
Set Frobber = CreateObject("BitBucket.Frobber")
Frobber.File = "c:blah.database" ' locks the file for exclusive r/w access
'
' Do stuff here
'
Set Frobber = Nothing ' final release on Frobber unlocks the file
'
' Do more stuff here
'
End Sub

Here we've got a lock on a resource that someone else might want to acquire, so it's polite to throw it away as soon as you're done with it. In this case it makes sense to explicitly clear the variable in order to release the object early, as we're not going to get to the end of its scope for a while. This is a particularly good idea when you're talking about global variables, which are not cleaned up until the program ends.

Another -- perhaps better -- design would be to also have a "close" method on the object that throws away resources if you need to do so explicitly.  This also has the nice result that the close method can take down circular references.

I can see how overapplication of this good design principle would lead to this programming practice. It's easier to remember “always set every object to Nothing when you are done with it“ than “always set expensive objects to Nothing when you are done with them if you are done with them well before they go out of scope“. The first is a hard-and-fast rule, the second has two judgment calls in it.

I'm still not convinced that this is the whole story though.

Explanation #4: I originally thought when I started writing this entry that there was no difference between clearing variables yourself before they go out of scope, and letting the scope finalizer do it for you.  There is a difference though, that I hadn't considered. Consider our example before:

Sub BlorbTheGlorb()
Dim Blorb, Glorb
Set Blorb = CreateObject("BitBucket.Blorb")
Set Glorb = CreateObject("BitBucket.Glorb")

When the sub ends, are these the same?

Set Blorb = Nothing
Set Glorb = Nothing
End Sub

versus

Set Glorb = Nothing
Set Blorb = Nothing
End Sub

The garbage collector is going to pick one of them, and which one, we don't know. If these two objects have some complex interaction, and furthermore, one of the objects has a bug whereby it must be shut down before the other, then the scope finalizer might pick the wrong one! 

(ASIDE: In C++, the order in which locals are destroyed is well defined, but it is still possible to make serious mistakes, particularly with the bane of my existence, smart pointers. See Raymond's blog for an example.)

The only way to work around the bug is to explicitly clean up the objects in the right order before they go out of scope.

And indeed, there were widely-used ADO objects that had this kind of bug.   Mystery solved.

I'm pretty much convinced that this is the origin of this programming practice.  Between ADO objects holding onto expensive recordsets (and therefore encouraging early clears), plus shutdown sequence bugs, lots of ADO code with this pattern got written.  Once enough code with a particular pattern gets written, it passes into folklore that this is what you're always supposed to do, even in situations that have absolutely nothing to do with the original bug.

I see this all over the place. Here's some sample documentation that I copied off the internet:

You can save an instance of a persistent object using its sys_Save method. Note that you must call sys_Close on an object when you are through using it. This closes the object on the server. In addition you should set patient to Nothing to close the object in Visual Basic.

Dim status As String
patient.sys_Save
patient.sys_Close
Set patient = Nothing

Notice that calling the close method is a "must" but setting the variable to Nothing is a "should". Set your locals to Nothing : it's a moral imperative! If you don't, the terrorists have already won. (One also wonders what the string declaration there is for. It gets worse -- I've omitted the part of the documentation where they incorrectly state what the rules are for using parentheses. The page I got this from is a mass of mis-statements -- calling all of them out would take us very far off topic indeed.)

I would imagine that there are lots of these in the MSDN documentation as well.

What is truly strange to me though is how tenacious this coding practice is. OK, so some objects are buggy, and sometimes you can work around a bug by writing some code which would otherwise be unnecessary. Is the logical conclusion “always write the unnecessary code, just in case some bug happens in the future?”  Some people call this “defensive coding”.  I call it “massive overgeneralization“. 

True story: I found a performance bug in the Whidbey CLR jitter the other day. There's a bizarre situation in which a particular mathematical calculation interacts with a bug in the jitter that causes the jitter to run really slowly on a particular method. It's screwing up our performance numbers quite badly.  If I change one of the constants in the calculation to a variable, the problem goes away, because we no longer hit the buggy code path in the jitter.

They'll fix the bug before we ship, but consider a hypothetical. Suppose we hadn't found the bug until after we'd shipped Whidbey. Suppose I needed to change my code so that in runs faster in the buggy Whidbey CLR. What's the right thing to do?

Solution One:   Change the constant to a variable in the affected method.  Put a comment as long as your arm in the code explaining to future maintenance programmers what the bug is, what versions of the framework causes the problem, how the workaround works, who implemented the workaround, and how to do regression testing should the underlying bug be fixed in future versions of the framework.  Realize that there might be similar problems elsewhere, and be on the lookout for performance anomalies.

Solution Two: Change all constants to variables. And from now on, program defensively; never use constants again -- because there might someday be a future version of the framework that has a similar bug. Certainly don't put any comments in the code. Make sure that no maintenance programmers can possibly tell the necessary, by-design uses of variables from the unnecessary, pointless uses. Don't look for more problems; assume that your heuristic solution of never using constants again is sufficient to prevent not only this bug, but future bugs that don't even exist yet. Tell other people that “constants are slower than variables“, without any context.  And if anyone questions why that is, tell them that you've been programming longer than they have, so you know best.  Maybe throw in a little “Microsoft suxors, open source rulez!” rhetoric while you're at it -- that stuff never gets old.

Perhaps I digress. I'd like to take this opportunity to recommend the first solution over the second.

This is analogous to what I was talking about the other day in my posting on Comment Rot. If you hide the important comments amongst hundreds of trivial comments, the program gets harder to understand.  Same thing here -- sometimes, it is necessary to write bizarre, seemingly pointless code in order to work around a bug in another object.  That's a clear case of the purpose of the code being impossible to deduce from the syntax, so call it out!  Don't hide it amongst a thousand instances of identical really, truly pointless code.

Comments

  • Anonymous
    April 28, 2004
    The good reason? ADO.

    Lots of the ADO samples in MSDN contain the Set <object> = Nothing, and for good reason, you don't want to keep database connections open (connection pooling aside) or tables locked.

    Of course there's always non-deterministic garbage control to through into the mix. Your object may fall out of scope, but who knows if it has been disposed yet. Not applicable to good old asp, but specifically calling dispose methods still applies in .net. Or does it? <g>

  • Anonymous
    April 28, 2004
    Not as bad as the Dim x as new xyz problems you get in VB. The only circumstances I've ever set stuff to nothing rather than letting the runtime do it is when destroying large collections. If you do it yourself then you can put up a progress bar, otherwise it looks like the worlds stopped (and if it's started swapping to disk then life is really bad)
    One possible reason is down to cut and pasting demo code which used to use globals perhaps?

  • Anonymous
    April 28, 2004
    In Access, it is 'convention' to do a .Close on all DAO.Recordset objects and DAO.Database objects, and set them = Nothing, like:

    Dim rs as DAO.Recordset
    Dim db as DAO.Database

    Set db = CurrentDB()
    Set rs = db.OpenRecordset("SELECT * FROM etc")
    'etc
    rs.Close
    db.Close
    Set rs = Nothing
    Set db = Nothing


    This is 'convention' because apparently there are/were bugs in earlier versions of Access (up to and including Access 97) where the Access window wouldn't close when you tried to close the application, no matter what you did. Ensuring your code always did the above fixed that problem.


    Here's a Google thread where Michael Kaplan [MS] hints at the bug, if not explicitly so:

    http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=active&selm=uLgaFdnX%23GA.226%40upnetnews05

    Also, here's something written by Michael Kaplan, though it confirms the bug in a straightforward manner, it is debunked three lines later:

    http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=active&selm=73i6a9%24158%40bgtnsc01.worldnet.att.net


    So, in summary:
    There are, or at least were, at one time, bugs that could be eliminated by ensuring we followed the 'convention'. Whether or not that is still the case, I don't know. Maybe get in touch with him; he's still around. Now I'm even more confused than when I began. But I'll still .Close/Set = Nothing everything until I hear different.

  • Anonymous
    April 28, 2004
    I don't think it's a myth because that's how we ended our query to a SQL 6.5 db from ASP 2.0. If we didn't, the db server would lock up, plain and simple.

    These days? Probably unnecessary, but if the code works, who am I to complain?

  • Anonymous
    April 28, 2004
    Matt Curland has made several posts about this on various VB newsgroups, confirming that setting local variables to Nothing immediately before they go out of scope isn't required, although admittedly there may have been good reasons for this in older versions of VB. I think this was Eric's point, there are of course times when you want to explicitly set a local object to Nothing before it goes out of scope, but it's not necessary to do it just before a local object goes out of scope.

    Some of Matt's arguments were:

    1. Why not also call SysFreeString and SafeArrayDestroy on your string and array variables if you don't trust VB to clean up after you?
    2. With statements generate hidden local variables, but you can't access them. If you use a With statement with an object, how are you going to set the hidden object to Nothing?
    3. It's inefficient because VB runs the same code again as part of its normal teardown. In fact, explicitly setting objects to Nothing results in a vbaCastObj call whereas the normal teardown results in faster vbaFreeObj calls.

    A collection of Matt's posts on the subject can be found here:

    http://tinyurl.com/3ajhk

  • Anonymous
    April 28, 2004
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  • Anonymous
    April 28, 2004
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  • Anonymous
    April 28, 2004
    The comment has been removed

  • Anonymous
    April 28, 2004
    The comment has been removed

  • Anonymous
    April 28, 2004
    Re: Matt Curland posts -- thanks for the links to those. Matt is The Man. One of these days I'll tell you guys about a conversation Matt and I once had about the differences between VBScript and VB's default property resolution Intellisense logic -- it is ARCANE to say the least.

    Re: ASP -- excellent point, and one that I had not considered. In ASP it is sometimes very difficult to know where you are and what scope you're in.

    However, just to clarify, my beef is specifically with people who clear object variables IMMEDIATELY before they go out of a local scope. It is a really good idea to clear variables that hold expensive resources as soon as you're done with them if you're going to go do other stuff before they fall out of scope.

    Re: Semicolon rules: I blogged about that already, see

    http://weblogs.asp.net/ericlippert/archive/2004/02/02/66334.aspx

  • Anonymous
    April 28, 2004
    Eric,

    I agree with you on this issue. Almost.

    In some older versions of ADO (I don't know if the problem has since been fixed, or if the real root cause was Q255986), if you raised an error before explicitly cleaning up local ADO recordets (closing them and setting them to nothing) you got:

    Method '~' of object '~' failed

    This meant you needed to:

    1. cache error details
    2. clean up recordsets (close and set to nothing)
    3. raise original error

    Search Google Groups (Advanced Search) using Message ID uRi4ddceBHA.186@cppssbbsa01.microsoft.com (see particularly the 4th point).

    Seeya
    Matthew

  • Anonymous
    April 28, 2004
    Take Outs for 28 April 2004

  • Anonymous
    April 28, 2004
    Setting objects to Nothing is a convention required by the company I work at, despite the fact that many advanced programmers here know it's not required. In fact, automatic cleanup is one of the better reasons to use VB at all, and having a convention to do it yourself makes the code a lot worse. I think our reasoning is that there are times where you have to set objects to nothing to deal with circular references, and that carried over into all uses of objects.

    I almost started laughing when I saw that your "random example" was from Intersystems, as we use Intersystems Cache for our back end database. However, we don't use any of the VB-integration features that that web page refers to.

  • Anonymous
    April 29, 2004
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  • Anonymous
    April 29, 2004
    The comment has been removed

  • Anonymous
    April 29, 2004
    Something else that I think muddied the waters a few years ago was when you stuck MTS or COM+ in front of the object you were creating. The client does a CreateObject, a wrapper in the interception runtime(MTS/COM+) is created and the 'real' object is owned by it not you. You get a ref to the wrapper back.

    The complexity introduced makes non-deterministic cleanup (by the VBA runtime) really hard (like impossible) if there are bugs in anything created by it(either directly or indirectly). That's where a lot of the method ~ of object ~ errors (as mentioned above) used to come from because MTS had noticed that things had gone badly wrong - unexpected ref counts etc.

  • Anonymous
    April 29, 2004
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  • Anonymous
    April 29, 2004
    The comment has been removed

  • Anonymous
    April 29, 2004
    The comment has been removed

  • Anonymous
    April 30, 2004
    > IServer::CreateObject keeps an internal list of objects it creates

    I have no idea whether that's true or not, and I haven't got the IIS sources handy anymore. I suppose that could be accurate -- it could be that the server needs to hold onto the objects to implement some of the transactability semantics?

    But I'm just guessing here. I would certainly have assumed that it did not hold onto any objects.

    Next time I need to debug into IIS and pull the sources down I'll check it out.

  • Anonymous
    May 01, 2004
    The comment has been removed

  • Anonymous
    May 03, 2004
    Another well-respected reference page which has some bearing on this subject is this:
    http://www.15seconds.com/issue/010514.htm

    As other posters have said, destroying objects ASAP probably became normal practice simply because of ADO. But there are plenty of badly-written COM objects around that might be suspect, and unless you've got the source who knows what might be left behind, so the accepted thinking is that it's preferable to take control and explicitly release resources as often as possible rather than leave it to what should be a foolproof garbage collection system in theory, but which is in reality likely to be less than perfect.

  • Anonymous
    May 08, 2004
    I did some empirical testing using a C++ COM object that we created in-house. The object's FinalRelease gets called whether or not you set the object to nothing. FinalRelease gets called even when you call Reponse.End to end the script.

  • Anonymous
    May 11, 2004
    Interesting insights into the background of Nothingness...
    For the present, in scripting circles, I would say it is now cargo cult stuff applied by imitation, like preceding each and every object name with an "obj". :)

  • Anonymous
    May 13, 2004
    The comment has been removed

  • Anonymous
    May 22, 2004
    I guess when a programmer has spent hours figuring that Close then Set to Nothing is the answer to an otherwise incomprehensible bug that learning sticks forever. (I've also seen cases where the flakiness wastes days and I've even seen "new technologies" that consume three months of a programmers life before they're thrown out because of some gotcha.)

    That's the danger of releasing flaky code. I'm with the defensive programmer on this. (Better programming that works than becoming an ex programmer in frustration!)

  • Anonymous
    May 22, 2004
    Perhaps the answer to all this would have been for Microsoft to be open about the ADO bug and have fixed it immediately.

    Therefore, to help prevent a similar practice in future, can we have a publically available .Net bug list? It should contain bugs that have not yet been fixed as well as bugs which have been fixed.

  • Anonymous
    May 23, 2004
    Bob Riemersma,

    Your example re: Excel is a red herring and does not relate to the issue at hand.

    As the MS support page clearly notes, the problem has nothing to do with the setting variables to Null / Nothing - it is to do with the fact that JScript uses garbage collection (while VB / VBScript uses reference counting).

    I would expect similar behaviour from any garbage collecting environment (such as .NET).

    You do state:

    <quote>
    In VBScript doing an XLApp.Quit doesn't result in Excel shutting down until you Set XLApp = Nothing or of course exit the scope of the variable containing the reference
    </quote>

    which is exactly Eric's point - setting XLApp = Nothing or letting it go out of scope are equivalent.

    Seeya

  • Anonymous
    May 25, 2004
    I would wager that this is due to one or both of the following: 1) an empirically derived rule, based on buggy automation implementations from "the good ol' days"; 2) well-meaning but wrong advice based on misunderstanding of scope, etc.

    Someone previously commented that Excel sometimes would get stuck in memory when invoked from Jscript. It wasn't the only app. In the mid-to-late 1990s timeframe, lots of devs were learning to write automation objects, and making the requisite mistakes along the way. Perhaps stuck apps were due to actual bugs in their implementation. Or, perhaps the bugs were due to references getting parked in global variables or in some intermediate scope. Setting "o = Nothing" is black magic that works, so why not do it everywhere? Regarding my second point: I'm a C++ developer, so the idea of scope, ctors & dtors, etc makes sense. But, for folks who started out with QBasic or Pascal and moved to VB, perhaps the idea of destruction was new. Granted, these languages did have scope, but especially with Basic, the paradigm (when I learned it, at least) was "all globals, baby!"

  • Anonymous
    May 28, 2004
    with apologies to Wm. Shakespeare...

    If setting objects to Nothing not be mandatory, it nonetheless remains useful from a documentation standpoint, since once an object is set to Nothing then the script should no longer make use of that object.

    Those obsessed with the "cargo cult" metaphorical aspect of this practice may merely treat it as documentation, while those who continue to implement the practice for other reasons can do so freely.

    And then we can all live happily ever after!8-))

  • Anonymous
    May 28, 2004
    Indeed, self-documenting code is goodness!

    But why stop at objects? Why not set strings and arrays and numbers back to their initial values to indicate that you're done using them?

  • Anonymous
    June 02, 2004

    I think that I located the source of this practice among VBScripters ... in the Holy Scripting Bible (otherwise known as SCRIPT56.CHM), there is a very oft used Method called "Run", and therein is an example at the end of said holy verse ...

    =====

    Example 2
    The following VBScript code opens a command window, changes to the path to C: , and executes the DIR command.

    Dim oShell
    Set oShell = WScript.CreateObject ("WSCript.shell")
    oShell.run "cmd /K CD C: & Dir"
    Set oShell = Nothing

    =====

    Oops !!, it seems that this practice is sanctioned by the Scripting Bible itself !?!? It spread viral-like from the holy book itself ... ;o)

    (i've often thought that if the SCRIPT56.CHM was updated - surely a long overdue task, the inconsistencies are confusing and many - then a lot of things could be cleared up just with a documentation revision !?) ;o)

  • Anonymous
    June 14, 2004
    I know it is a bit late to comment on this blog, but I have just experienced one of those cases in VB6, where setting an object reference to Nothing made a difference.

    In this case, I have a UserControl which implements an custom interface using the Implements keyword. A form using this control stores an interface pointer (of this custom interface type) to the control.

    Initially, the VB6 application crashed on exiting. After setting the interface pointer to Nothing, the program no longer crashed on exiting.

    In face, I have often seen this kind of problem, if you store an interface to a control on a VB6 form.

    For example, if a form passes an interface to one of its controls to another form, then that other form had better free the interface. Otherwise the program will probably crash on exiting. (To be fair, this is a lousy practice anyway, but quite legal VB6).

    I wish these cases did not exist, but it does seem naive to believe that they don't.

    Phil

  • Anonymous
    July 10, 2004
    The comment has been removed

  • Anonymous
    July 15, 2004

    Performance Question:

    We make a large collection of many objects. It seems to take longer (several minutes) to clean up the objects than to create them (under a minute). How can we clean them up faster? We just want them to all go away.

    We've tried similar tasks in C++ and Java and both are sub-second to create and delete millions of similar objects. VB takes about a minute to create and several minutes to delete.

    We've tried letting VB clean up automatically, and we've also tried to explcitly set the objects and the collection to nothing. Nothing seems to get it going any faster.

  • Anonymous
    July 15, 2004
    Clearly something weird is going on. But there's nowhere near enough information for me to diagnose the problem.

    I would try running the slow code through a profiler and see what it comes up with. If that doesn't help, the best I can suggest is a support call -- make up a small, solid repro that demonstrates the problem, and call it in.

  • Anonymous
    July 15, 2004
    we've run side by side tests of simple samples. Creating 1 million instances of simple objects (3 members, 1 Str, 1 Double, 1 Int) and addint them to basic collections. We've then tried deleting the collection and deleting the objects individually.

    We've done this in VB6, C++, and Java. Java and C++ complete the whole thing sub second. VB app takes almost a minute to create and several minutes to clean up. VB app freezes during the clean up but eventually completes.

    The item above by Peter Ibbotson at 4/28/2004 12:05 PM sounds exactly like what we are experiencing. We just accepted that VB was this slow but are hoping that there is some way to delete these objects more efficiently.

  • Anonymous
    July 15, 2004
    Same collection object in each case, or is it a different object in each?

    My guess -- which, I will point out again, is a guess in total absence of actually seeing the scenario -- is that some collection objects are optimized for large sets and some are not, and perhaps that is the nature of the problem?

  • Anonymous
    July 15, 2004
    The comment has been removed

  • Anonymous
    July 15, 2004
    I believe you that its slow. I don't know whether the collection class was even designed to handle collections of that size.

    My point though is that comparing this code against the "equivalent" code in C++ is not actually a valid comparison unless the C++ code uses exactly the same collection object. If the C++ code uses the same collection object AND it is still faster, then odds are very good that there's something wrong in the language engine. If it is just as slow, odds are very good that the problem is in the collection class.

    What collection objects do you use in the C++ and Java benchmarks?

  • Anonymous
    July 18, 2004
    In C++ and Java the tests were done with regular lists, not the same Collection class used in VB.

    But we've also tried a test in VB where we use a linked list rather than a collection. It is faster, but deleting the objects still takes much longer than it should.

  • Anonymous
    July 19, 2004
    Then you're not comparing apples to apples, are you? If you want to find out what's slow, you don't change everything. You change one thing at a time.

    Odds are very good that it's the collection object that's slow.

    In any event, is this a meaningful benchmark? Are you actually writing a program that must handle millions of data which are allocated and deallocated frequently? In that case I would recommend that you either (a) use a language which allows you fine-grained control over memory lifetime -- like, say, C++, or (b) use a language which runs in an environment with a specially tuned garbage collector, like C# or VB.NET.

  • Anonymous
    July 19, 2004
    I wish we had done it in C++.

    Our basic need is to create a list of structs to hold some data properties. We create them all at once, we use them, then we delete them all at once.

    Creating and using them is pretty fast. It's just deleting them that takes long. Which makes me wonder if we are doing something wrong. But it sounds like we did things the accepted way and this is just the built-in penalty for using VB.

    I was hoping there was some trick to speeding it up like there is for strings. We also need to concat large strings from many small parts. We started by using the STR1 = STR1 & STR2, which was slow. We replaced it with a string buffer and it sped up literally tens of thousands of times faster for very large strings.

    But it sounds like no such workaround is available for objects.

  • Anonymous
    February 14, 2006
    I know it's been a long time since this article was active but I had a 1/2c to throw in.  I think the underlying reason could be as simple as: lots of VB coders probably started life as C/C++ coders.  They knew they had to free their allocated objects before they went out of scope and can't get used to the idea that VB will do it for them.

  • Anonymous
    June 01, 2006
    The comment has been removed

  • Anonymous
    May 12, 2008
    To Barry Dorrans : I disagree - if you have an open connection to a db you close it not set it to Nothing connection.close which is different from what this article is talking about....

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  • Anonymous
    January 25, 2011
    Am I the only one who noticed that half this article repeats itself? Also, @Pete, C++ programmers would not make that mistake, they are used to local variables cleaning themselves up nicely.

  • Anonymous
    April 02, 2012
    Hi there. I do not speak English and I did not understand any of the writings. <% Dim zz zz = "Hello World" Response.Write (zz) Set zz=Nothing %> Is it true? Please answer in simple terms.