My firm's Access database has been having some serious problems recently. The errors we're getting seem like they indicate corruption -- here are the most common:
Error accessing file. Network connection may have been lost.
There was an error compiling this function.
No error, Access just crashes completely.
I've noticed that these errors only happen with a compiled database. If I decompile it, it works fine. If I take an uncompiled database and compile it, it works fine -- until the next time I try to open it. It appears that compiling the database into a .ACCDE file solves the problem, which is what I've been doing, but one person has reported that the issue returned for her, which has me very nervous.
I've tried exporting all of the objects in the database to text, starting with a brand new database, and importing them all again, but that doesn't solve the problem. Once I import all of the objects into the clean database, the problem comes back.
One last point that seems be related, but I don't understand how. The problem started right around the time that I added some class modules to the database. These class modules use the VBA Implements keyword, in an effort to clean up my code by introducing some polymorphism. I don't know why this would cause the problem, but the timing seems to indicate a relationship.
I've been searching for an explanation, but haven't found one yet. Does anyone have any suggestions?
EDIT: The database includes a few references in addition to the standard ones:
Microsoft ActiveX Data Objects 2.8
Microsoft Office 12.0
Microsoft Scripting Runtime
Microsoft VBScript Regular Expressions 5.5
Some of the things I do and use when debugging Access:
Test my app in a number of VM. You can use HyperV on Win8, VMWare or VirtualBox to set up various controlled test environments, like testing on WinXP, Win7, Win8, 32bit or 64 bits, just anything that matches the range of OS and bitness of your users.
I use vbWatchDog, a clever utility that only adds a few classes to your application (no external dependency) and allows you to trap errors at high level, and show you exactly where they happen. This is invaluable to catch and record strange errors, especially in the field.
If the issue appears isolated to one or a few users only, I would try to find out what is special about their config. If nothing seems out of place, I would completely unsintall all Office component and re-install it after scrubbing the registry for dangling keys and removing all traces of folders from the old install.
If your users do not need a complete version of Access, just use the free Access Runtime on their machine.
Make sure that you are using consistent versions of Access throughout: if you are using Access 2007, make sure your dev machine is also using that version and that all other users are also only using that version and that no components from Access 2010/2013 are present.
Try to ascertain if the crash is always happening around the same user-actions. I use a simple log file that I write to when a debugging flag is set. The log file is a simple text file that I open/write to/close everytime I log something (I don't keep it open to make sure the data is flushed to the file, otherwise when Access crashes, you may only have old data in the log file as the new one may still be in the buffer). Things I log are, for instance, sensitive function entry/exit, SQL queries that I execute from code, form open/close, etc.
As a generality, make sure your app compiles without issue (I mean when doing Debug > Compile from the IDE). Any issue at this stage must be solved.
Make absolutely sure you close all open recordsets, preferrably followed by setting their variables to Nothing. VBA is not as sensitive as it used to be about dangling references, but I found it good practice, especially when you cannot be absolutely sure that these references will be freed (especially when doing stuff at Module-level or Class-level for instance, where the scope may be longer-lived than expected).
Similarly, make sure you properly destroy any COM object you create in your classes (and subs/functions. The Class_Terminate destructor must explicitly clean up all. This is also valid when closing forms if you created COM objects (you mentioned using ADOX, scripting objects and regex). In general keeping track of created objects is paramount: make sure you explicitly free all your objects by resetting them (for instance using RemoveAll on a dictionary, then assigning their reference to Nothing.
Do not over-use On Error Resume or On Error Goto. I almost never use these except when absolutely necessary to recover from otherwise undetectable errors. Using these error trapping constructs can hide a lot of errors that would otherwise show you that something is wrong with your code. I prefer to program defensively than having to handle exceptions.
For testing, disable your error trapping to see if it isn't hiding the cause of your crashes.
Make sure that the front-end is local to the user machine, You mention they get their individual front-end from the network but I'm not sure if they run it from there or if it it copied on their local machine. At any rate, it should be local not on a remote folder.
You mention using SQL Server as a backend. Try to trace all the queries being executed. It's possible that the issue comes from communication with SQL Server, a corrupt driver, a security issue that prevents some queries from being run, a query returning unexpected data, etc. Watch the log files and event log on the server closely for strange errors, especially if they involve security.
Speaking of event log, look for the trace of the crash in the event log of your users. There may be information there, however cryptic.
If you use custom ribbon actions, make sure thy are not causing issues. I had strange problems over time with the ribbon. Log all all function calls made by the ribbon.
Related
I have an access front-end that connects to SQL Server tables and works fine. When I compile it into an accde file however, I get various errors when closing the DB. The errors seem to indicate that the program is still looking for a table or the value of a global variable. There is a routine in the Form_Close() event of a hidden form that Deletes all the links to the SQL Server back-end. So, how can I debug an already compiled access database? Why does the compiled DB behave differently than the uncompiled (accdb) version?
You need to trap errors using On error goto LabelName or if you don't care about errors you should use On error resume next on top of your code. You should still post your code to get more accurate help.
Are you talking about the same computer, or different computer?
The compiled accDE are VERY sensitive to being executed on a different machine (even the same version). The reason for this is that the compiled accDE takes on your current office release version.
In terms of global variables, and error handling?
accDE's are the BEST choice, since un-handled errors does not re-set local, or even global variables. In effect, a accDE runs like a un-stoppable freight train.
if your accDB (un-compiled) works and runs fine on your computer, then I have NEVER seen a case in which the accDE does not run, and in fact run better and behavies far more ro-bust.
So, no, you can't debug the accDE, but you can the accDB on the SAME computer.
If you are running the accDE on a different computer, then you left out a massive, huge and SPECTUALAR bit of information in your post.
If you ARE running the accDE on the same computer (that you created it with), then about the only possible is that the accDE file extension is using a different version of access to run with. This is rare - I would thus from the control panel, applications and features find your version of access and right click and do a repair on your office install.
The issue of patch version of office/access is VERY significant here. The reason of course is that if you deploy the accDB, it will often work because access can (and does) detect that the current version (even SP/patch/update) level of Access is different, then it can re-compile the code on the fly (because the accDB has the source code). The accDE does not, and thus it can't re-compile. However, I still STRONG suggest you deploy the accDE and resolve the SP/patch level issue since a accDE is oh so much more reliable in its operations compared to un-compiled accDB's.
I would be rather stunned if you are experiencing this issue on the same computer running the accDB and that computer is then used to create the accDE. If this is the actual case, then I would create a new blank accDB, and import everything from the old accDB, and then ensure it can compile the code (from IDE debug->compile). If the app compiles, then create the accDE, and it should work just fine. So, if this is same machine, then your accDB is damaged or corrupted. As I stated, create a new one, import everything from old, and create your accDE from that. It will work, and I never seen a case in which a accDB works, and a accDE does not work (on same machine).
1st thing to do is to decompile your application ...just Google Ms Access Decompile.
When you perform the Decompile and try to compile is almost certain that you will find some "forgotten" mistakes.
2nd if 1st fails its time to implement a robust logging system...based on text file writing, in order to avoid dependencies just work low : https://learn.microsoft.com/en-us/office/vba/language/reference/user-interface-help/freefile-function.
If it still fails post back with more info.
I'm seeing a strange build bug a lot. Sometimes after typing some code we receive the following build error.
Class 'clsX' must implement 'Event PropertyChanged(sender As Object, e As PropertyChangedEventArgs)' for interface System.ComponentModel.INotifyPropertyChanged'.
And
'PropertyChanged' cannot implement 'PropertyChanged' because there is no matching event on interface 'System.ComponentModel.INotifyPropertyChanged'.
Those error should never go together! Usually we can just ignore the exception and build the solution but often enough this bug stops our build. (this happens a lot using Edit and Continue which is annoying)
We're using Vb.net and c# mixed in one big solution.
Removing the PropertyChanged event and retyping the same code! sometimes fixes this.
Question:
Has anyone else seen this problem and has some suggestions how to prevent his?
We're using a code generator that causes this error to surface but just editing some files manually triggers this exception too. This error occur's on multiple machines using various setups.
Someone had the same exact issue discussed here. It sounds like there is an issue with this build picking up an old version of a binary. I would try the following in order:
Verify all assembly references use project references where possible within the Visual Studio solution.
Disable build parallelization in case there is some weird file locking issue with concurrent project builds. Go to Tools -> Options, Projects and Solutions -> Build and Run, then set "maximum number of parrellel project builds" to 1. Not the best solution but it may help narrow down the problem.
Disable the Hosting Process in case it's locking some file causing an assembly to not get rebuilt correctly. For C# project go to Project Properties, Debug tab, and uncheck "Enable the Visual Studio hosting process". For VB.NET project you'll need to Unload Project, Edit the project file, and add <UseVSHostingProcess>false</UseVSHostingProcess> to the PropertyGroup of each configuration. Again, not the best solution but you probably won't notice a difference.
Lastly, try doing a Clean + Build to try and resolve the issue when it occurs (I know this is not a fix but it's easy enough to do), also Rebuild may be slightly different than Clean + Build so try the latter if the former doesn't work.
As I can not comment due to lack of appropriate points.
But I would like to share one of my experience:
In an aspx.cs page I was working, used to compile fine and some time gave mysterious error of a variable not defined or function not defined or sometime variable or the function defined two times. I changed possibly each and every variable and function name but there seemed no effect , but after entering a simple space or a new line at any place in the file used to solve the compile error. At one time I tried to save the file (in a different encoding as i am used to experiments) and found that the file was not saving in the correct encoding (i.e. the ansi encoding because the file had a unicode character ), I removed the unicode character and that compile error didn't bothered me again.
This unicode character problem could be (not a hard and fast rule) there so you could check it.
Nuke & restore using source control (TFS instructions here):
Make sure you have everything checked in
Exit Visual Studio
Rename the project directory to .Bak (effectively deleting it)
Reopen Visual Studio and in source control:
Get Specific Version
check 'Overwrite... not checked out' and 'Overwrite ... even if local version matches'
Re-open project
Another problem: Make sure some source files are not newer than the current date (or your date is set back). Often this happens in apps where you are doing logic that requires certain things to happen differently on certain dates. You change your clock to test it, make a revision to the source with the date advanced, set the date back, and viola, rebuild does not rebuild that file.
You say 'typing it in again' - can you try just saving? After 40 years since MULTIX the .net build still decides what has changed by checking the file timestamp.
good luck!
When you get the error, is it always on the VB calling C# side, or vice-versa, or does it work both ways?
If the answer is either of the first two situations, try building the "callee" project within the solution before building the "caller" project to see if it stops the situation.
Also, just in case it may jog something for you to think about, does this error crop up when you change a VB file or a C# file, or is there no correllation?
Oh, and sorry this looks like an answer instead of a comment, I cannot post comments yet (need 50 rep).
I have an old VW3/ENVY image with a parcel loaded as unmanaged code (exactly the situation Mastering ENVY/DEVELOPER warns against). Unfortunately, this problem happened a long time ago and it's too late to just "go back" to an image without the parcel loaded.
Apparently, there is a way to solve this problem (we have one development image where this has been solved, and there are normal configuration maps that contain the exact same code as the unmanaged parcel but they can't be loaded), but the exact way has long since been forgotten (and there are some problems with taking that particular dev image as the base for a new runtime image, so I need to find out how how to do it again).
In theory, it should be possible to remove the parcel and reload the code from a configuration map. In practice, all normal ways (using the ParcelBrowser or directly calling UnmanagedCode>>remove) fail. I even tried manually removing the offending selectors from the method dictionary, but past a certain point (involving a call to #primBecome:) the whole image hangs completely (I can't even drop into the debugger). I started hacking the instances of the classes and methods, hoping I'd trick ENVY into thinking that these particular methods are normal versioned code, but without any success yet.
Are there any smalltalk/envy gurus around that still remember enough of VW 3 to provide me with any pointers?
Status update
After a week of trying to solve the problem I finally made it, at least partially, so in case anyone's interested...
First, I had to fix file pointers for the umnanaged code (otherwise, all everything that tried to touch the methods would throw an exception). It looks like ENVY extends Parcel so that, in theory, all integer file pointers are changed to ENVY's void filepointer when loaded, but in my case, I had to do it manually (a Parcel provides enumeration for all selectors it defines). Another way would be to tweak the filePointer code, but that can't easily be done automatically on every image where it's needed.
Then, the parcel can be discarded, which drops the parcel information, but keeps the code. The official "Discard" mechanism needs to have a valid changes file (which envy doesn't use so it has to be set manually, and reset afterwards) and the parcel source (which we fortunately had).
To be able to make any changes to the methods (either manually, or via loading an application or class from ENVY), they need to get rid of their unmanaged status. This can be done by manually tweaking TheClass>>applicationAssocs (I also got rid of all references to the classes in UnmanagedCode sich as timestamps, and removed the reference to the discarded parcel). I actually had some info on how to get to this point from my boss, but I haven't been able to understand the instructions until I almost figured it out by myself.
This finally allowed me to load and reload all the Applications that contained the classes. In theory. In practice, the image still hung completely whenever I tried to load a newer version of the Application (that contained the code formerly in the parcel).
It turned out that the crashes had absolutely nothing to do with the code being unmanaged, but with the fact that the parcel in question modified InputState>>process:, where it caused an exception due to a missing and/or uninitialized class variable (the InputState>>initialize method wasn't called until after the new process: method was in place). I had to modify the Notifier class to dump all exceptions to a file to find out what was going on. Adding the class variable to the source of the class (instead of adding it via reflection), suspending the input processing thread via toBeLoadedCode and starting it again in the loaded method and creating a new version of the application solved even this problem.
Now everything works, in theory. In practice it's still unusable, because reloading the WindowSystem or VisualworksBase applications causes their initialization blocks to run, and a whole lot of settings are reset to their defaults - fonts and font sizes, window colors, UI settings... And there doesn't seem to be any way to just save the settings to a file and load them later on, or just to see what all the settings are (either the official Settings menu doesn't show everything, or we have a heavily tweaked image... so much for reconstructing it from scratch). But that's a completely different question.
Well, normally the recommendation would be that you should be able to rebuild your development image from scratch by loading your code from the repository. But if you had that, then the answer would be simple, just discard that image and reload. I think it's been long enough that I've lost whatever knowledge I've had about how to mess with the internal structures to get it back, and it sounds like you've tried a lot of things. So, although it might be painful, figuring out the recipe to rebuild your development image by loading stuff from the repository sounds like it may be your best bet. It probably isn't all that horrible, there just might be a few dependencies on the image state, or special doits that need to be executed.
You also probably need to validate what's in the repository against what's in the image you're working from. If there was unmanaged code loaded and then someone modified it and saved it, it's not clear to me that it would have been saved to ENVY. So you probably want to audit everything that was unmanaged code and if it's been changed, save that to a repository edition.
Sorry I don't have any better answers.
Assuming self-registration is used to install components as part of a larger installer program, why is self-registration bad? E.g. self-registering vb custom controls or capicom or whatever. I acknowledge that self-registration is probably not as safe in the case of a dll you wrote yourself, but I'm not discussing those.
The MSDN lists several reasons why self-registration is bad, reproduced here:
Rollback won't work properly.
OK, this reason makes sense.
Advertisement will not work as well.
Ignoring the fact that advertisement is only important for certain types of software clients, I don't understand why this is an issue. Only the main application needs to be advertised, not its components.
Self-registration does not support per-user keys properly.
So what? Giving every user access to "common" components is not a bad thing unless you have a lot of users on the machine, in which case it's still not world-ending.
Self-registration is more susceptible to coding errors.
I can definitely believe this, except in the case of dlls which were written by Microsoft (they may have errors, but I don't think trusting them is unreasonable). And in the case of tlbs and ocxs which were generated by software, coding errors seem pretty unlikely.
Self-registering dlls may link to other dlls.
In the case of dlls generated by programs, it doesn't seem likely that self-registration will fail due to this but adding the registration keys manually would have worked. I'd rather have my self-registration return an error that I'm missing the dlls.
I'm sure this will draw flames :/
Edit: Crossed out arguments that I think actually matter (based on user responses and my own).
As far as this item:
Self-registration does not support per-user keys properly.
So what? Giving every user access
to "common" components is not a bad
thing unless you have a lot of users
on the machine, in which case it's
still not world-ending.
It's not just a matter of how many users are on a machine, but also what permissions they have. If not an administrator, the user will be unlikely to have permission to update the HKEY_LOCAL_MACHINE portion of the registry.
The item
Self-registering dlls may link to
other dlls
applies when you try to register the dll, but the installer has not yet copied/installed another dll your registering function requires.
I would add one potential "gotcha" which I have run into (with auto-generated self-registration code for MS COM objects):
Self-registration runs the executable, with all that entails/requires. So, for example, if your component directly or indirectly logs the fact that it was activated (perhaps for security logging if the component is only supposed to be running at very specific points or in very specific contexts, or in coordination with other applications), registration will appear to be an activation (unless you're careful about logging). This can also be interesting if your logs record, say, the context in which the component was utilized, in which case you will have whatever inherited context triggered the self-registration.
Not a big deal in most cases, but it can cause some subtle confusion sometimes. I'd add it to the list of reasons why it's probably not preferable.
I'm new to VB6 but i'm currently in charge of maintaining a horror of editor like tool with plenty of forms, classes, modules and 3rd party tools all chunk together like the skin faces on that guy in the texas chainsaw massacre...
What i don't understand is why i get different results when i run the app in debugging mode, vs when i compiled it and run it on my devevelopment pc vs when i installed it on a different pc.
Yes i know i'm dumb, so please direct me to where i can find out more about this. I'm hoping to find out something like different linking, registry related etc connection that i'm simply not getting right now, i.e. something like wax on, wax off :P
The main pain in the neck is when i'm trying to debug some errors from my QA and i need to find a spare pc to test this on plus i can't directly debug because i don't know where the code is if i do it that manner.
Thanks.
i run the app in debugging mode vs when i compiled it and run it on my
devevelopment pc
When you compile you have the option of compiling to native code or pcode. The debugger runs using pcode only. Under rare circumstances when you compile to native code there will be a change in behavior. This particular is really rare. I used VB6 since it's release and I may get it once or twice a year. My application is a complex CAD/CAM creating shapes and running metal cutting machine and has two dozen DLLs. Not a typical situation. At home with my hobby software I never ran into this problem.
There are another class of errors that result from event sequencing problems. While VB6 isn't truly multi-tasking it has the ability to jump out of the current code block to process a event. If it re-enters the same block for the new event interesting things (to say the least) can result. I think this is the likely source of your problems as you software is an editor which is a highly interactive type of software.
In general the problem is fixed by reordering the effected areas. You find the effected area by inserting MsgBox or write to a text file to log where you are. I recommend logging to a text file as MsgBox tend to alter behavior that are timing or multi-tasking related.
Remember if a event fire while VB6 in the middle of a code block and there a DoEvents floating around then it will leave the code block process the event and return to the original code block. If it re-enters the same code block and you didn't mean for this to happen then you will have problems. And you will have different problems on different computers as the timing will be different for each.
The easiest way to deal with this type of issues is create some flag variables. In multi-tasking parlance they are known as semaphores or mutexes. WHen you enter a critical section of code, you set it true. When you leave the routine you set it to false. If it is already true when you enter that section of code you don't execute it.
when i installed it on a different pc.
These are usually the result of the wrong DLL installed. Most likely you have an older version while the target has a newer version. I would download the free Virtual PC and create a clean Window XP install to double check this.
If your problem is event timing this too can be different on different computers. This is found by logging (not MsgBox) suspect regions.
If you can display a screen shot or the text of your specific errors then I can help better.
The first thing to check would be the versions of all the dlls that your app depends on - including the service pack version of the VB6 dll.
Have you any more specific details about what's behaving differently?