Posts filed under 'MSAccess'
I’m currently researching ways to move my main MS Access application from a simple local network client/backend setup to a global, multiple remote sites configuration using SQL Server.
One of the challenges is to upsize the current MS Access 2007 backend database to SQL Server 2008.
If you try it from Access itself using the Upsizing Wizard, you may end up getting this error message:
The Upsizing Wizard only works with Microsoft SQL Server (Versions 6.50 SP5 or higher). Please log in to a SQL Server data source.
After spending some time fiddling around with SQL Server settings I couldn’t understand why I was still getting this error.
Turns out that the upsizing wizard is apparently sensitive to the version of SQL Server you’re using and it doesn’t consider SQL Server v10 (2008) as being later than v6.50…
This issue is in fact a blessing.
Microsoft provides a migration tool for upsizing MS Access database to SQL Server 2008 that’s orders of magnitude better than anything the basic wizard can do: the SQL Migration Assistant for Access, or SSMA.
SSMA lets you take a bunch of Access databases and move the tables and queries you choose to SQL Server, automatically linking them in your original database if you want.
It’s not just a one-off thing either: SSMA keeps track of the objects that where transferred and allows you to synchronise both schema and data as often as you need.
So here you are: do not use the basic MS Access Upsizing Wizard, download and use SSMA instead.
Strange COM Error
While SSMA works perfectly fine on my Windows 2008 x64 laptop, on my main Windows XP desktop it throws an exception when trying to load an Access database:
Unable to cast COM object of type ‘Microsoft.Office.Interop.Access.Dao.DBEngineClass’ to interface type ‘Microsoft.Office.Interop.Access.Dao._DBEngine’
… {00000021-0000-0010-8000-00AA006D2EA4}…
It was a COM error saying that the library for DAO couldn’t be loaded.
I couldn’t find any relevant information on the web.
After a while, I had a look at the DAO driver in
C:\Program Files\Common Files\Microsoft Shared\DAO\dao360.dll
and I noticed that the filename was in blue: that reminded me that I had set compression on the filesystem.
I disabled compression for the file and, magically, SSMA worked again…
Moral of the story: be careful about compressing your filesystem, some registered libraries and system files may work in unpredictable ways…
References
Updates
- 17MAR2009: Added section on the strange COM error.
- 14MAR2009 : Added links to Tony’s Access MVP website.
- 05JAN2009 : Original publication.
March 17th, 2009
My trusty old gigantic Sony Vaio is about 4 years old. It served me well and still works but it’s about to become my main development machine for the next couple of months and I can’t afford to have it die on me during that time.
It was time to get something as gigantic and more up-to-date in terms of technology.
I use VMware on my main desktop to keep multiple OS setups that match typical configurations of my customer’s machines.
This allows me to test my software before deployment and make sure everything works as expected.
It saved me many times from strange bugs and I would consider these final tests to be a mandatory step before deployment.
My old trusty vaio would be hard pressed to run any of these without slowing down to a crawl.
I looked at some possible replacements. Initially I checked Lenovo’s offerings but they don’t seem to offer anything in large screen size (WUXGA 1920×1200) (Note, actually, they have, but not really for me).
Dito for Dell, not counting their humongous XPS M1730 luggable gaming machine that was wayyy over the top as a work computer, not to mention probably heavier than its volume in pure gold.
On a hint from a friend I checked out Apple’s online store and saw they had a nice Macbook Pro configuration. I went to check it out in the retail store close to my office and they had that exact specification in stock, so, in what must have been the highest rated expense/time-to-think ratio of any decision I ever took, well, I bought it…
The spec, some bragging rights:
- Macbook Pro 17″
- Core Duo T9500 2.6GHz processor
- nVidia 8600M GT 512MB graphics card
- 200GB 7200rpm drive
- Kingston 4GB DDR2 667MHz RAM
- Hi Resolution 17″ 1920×1200 glossy screen
It’s a very nice machine, Apple knows how to make nice hardware, there is no question there.
OSX has some cool features, some of them still a bit foreign to me and some minor annoyances are creeping up, like Thunderbird’s not picking up my system date and time settings and displaying the date in the wrong format (a pet peeve of me), probably not Apple’s fault but annoying nonetheless.
So far so good and while I don’t mind using OSX for my browsing, email and creative stuff, that machine is meant to be running Windows Server 2008 x64 as a development platform.
Why Windows Server 2008 x64?
Well, it has some excellent features, a smaller footprint than Vista, all the aero eye candy, is apparently noticeably faster than Vista and has none of the nagging security prompt (you are considered administrator though, so keeping safe is entirely up to you).
The 64 bit version can also address the full 4GB of RAM without limitation and all server features are optionally installable.
By default, the installation is actually pretty minimal and you have to set services and options to get Windows configured as a proper workstation. It is after all, meant to be a server.
Oh, I almost forgot that there is also support for HyperV, although you must make sure you download the right version (if you list all available downloads in your MSDN subscription, you’ll see some that are explicitly without that technology).
Installing Windows Server 2008 x64 is remarkably easy.
- Get your hands on the ISO from your MSDN subscription or an install DVD from somewhere else (like a MS event, or even as a free 240 days download from Microsoft).
- You’ll need to repackage the ISO as it won’t work properly (something to do with non-standard file naming options).
It’s fairly easy if you follow the instructions from Jowie’s website (cached version): you can get the ImgBurn software for free as well, which is a good find in itself. It should’t take more than 30 minutes to repackage the DVD.
- In OSX, go to Applications > Utilities > Boot camp and follow the instructions on screen.
You will be able to resize the default partition by just moving the slider. I left 60GB for OSX and allocated the rest to Windows. The good thing is that OSX can read Windows partitions, so you can always store data there. Windows however, can’t read the HFS+ mac file system, although there are some third-party tools that can do it [1] [2] [3].
- Insert your repackaged DVD and Bootcamp will have rebooted the machine.
After a few minutes of blank screen (and no HDD activity light to let you know something is happening), windows setup launches.
- You will be then prompted with the choice of partition to install to.
Select the one named BOOTCAMP, then click the advanced options button and click format.
From there one, windows will install everything, then reboot, then carry on installing, then reboot one last time.
- Now, insert your OSX recovery CD 1. It should automatically launch the driver installation.
Once done, you’ll reboot to a nice, full-resolution windows prompt.
- All drivers will have been installed correctly except the one for Bluetooth. To easily solve that issue, just go to Spencer Harbar’s website and read how to install the Bluetooth drivers. Takes 5 minutes tops.
The final touches
A few notes to quickly get things running as expected.
- Get the most of your configuration by following the list of tweaks from Vijayshinva Karnure from Microsoft India.
- There are more tweaks, and even more tweaks available as well (don’t forget to enable Superfetch).
- Microsoft has a whole KB entry on enabling user experience.
- In the Control Panel > System > Advanced System Settings > Advanced > Settings > Advanced > Processor scheduling, set to Programs instead of Background services.
- Activate your copy of Windows using Control Panel > System.
I was getting an error code 0x8007232B DNS name does not exist error. To force activation, just click on the Change Product Key button and re-enter the same key you used during install.
Windows will activate straight away.
- When booting your Macbook, press the Option key and you will be presented a list of boot choices.
- You can check on Apple’s Bootcamp webpage other information about how to use the track pad, keyboard layouts etc,
References
August 31st, 2008
Access programming is inherently single-threaded. That’s usually OK as most operations are sequential anyway and it keeps things simple at the programming level.
There are times though where the lack of ability to run code on another thread is sorely missing: anything that takes a long time to run will just freeze the application, making it unresponsive and appearing to be locked and about to crash to the user.
Checking for the existence of network paths
Checking for the existence of network paths (directories or files) is one of these issues that can freeze an application for 30 seconds or more if the folder is not accessible.
This is a type of problem that benefits greatly from running in a separate thread: it can take such a long time that the best way to check for these remote paths is to launch the verification for their existence outside of Access and somehow get the result back and cache it for the current session so we don’t have to suffer these delays again every time we check for that path’s existence.
One easy way to do achieve that goal is to create plain DOS batch files that execute hidden from view, create a result file when they complete their task and delete themselves automatically when they are finished.
How to use it
Download the sample database below then just add the FileUtilities, HashTable and MD5 modules to your project and you can use the code as such:
The status variable will return either of the following values:
AsyncDirectoryStatus.OK if the path was found.AsyncDirectoryStatus.NotFound if the path was not found (either because it doesn’t exist or you don’t have the rights to access it).AsyncDirectoryStatus.Checking if the verification is in progress and we haven’t received a definite answer yet.
It’s up to you to decide how you want to handle that case. You could periodically check it, like I did in the example database, or you could disable the controls until you’re getting a confirmed result (by checking every time the user performs some action, like moving from record to record in a datasheet for instance).
You can call PathExistAsync as often as you want to check the status: it will not slow down your application (read the optional arguments section below though).
The result of the verification is cached, so querying the existence of the path is actually only done once; the result of subsequent queries for the same path is just instantly retrieved from memory.
Optional arguments
If you want to force the actual re-checking of a path without using the cached value, you can simply pass the ForceCheck optional parameter:
The first time you query for a path (or force it to be rechecked) there will be a short 150ms delay to give a chance to the function to return its result straight away (in case the path can be resolved quickly).
This may not be desirable if you’re checking a bunch of directories at a time. For instance, this is what I do when my application launches:
By querying the existence of all these paths as soon as my application launches, I am starting the verification process without introducing delays in the application itself: each verification will start in its own process, in parallel to the main application.
Later in the application, when I need to actually use these paths, their result is likely to be known.
How it works
The FileUtilities module contains the main code.
In it, the PathExistAsync function works in slightly different ways depending on whether it’s the first time it is being called for a particular path or not.
The first time
The first time the function is called for a given path, we create in the user’s temporary folder the small batch file whose name is simply a MD5 hash (see below) of the path with .bat appended to it.
This batch file simply checks for the existence of the path and will create a small file (whose name is the MD5 hash of the path) with either 0 or 1 in it depending on the result of the verification.
We initially cache the status of the verification for the Path into the AsyncDirectories hashtable (see below) as Checking.
Example of batch file automatically created to verify a path:
The Batch file name is 463C7367D8329BD6209A65A70A7DA08C.bat where the long number is actually the MD5 hash of the path we’re checking \\123.56.78.9\going nowhere.
Getting back the result
Whenever the PathExistAsync function is called, we check the currently cached result from the AsyncDirectories hastable.
If it is still Checking then we try to verify if we the result file has been created from the running batch. If not, we just return the same status, if yes, we read the result from the file, save it in the hashtable and delete the result file.
Useful libraries
The code makes use of 2 extremely useful libraries that I end up using quite often:
a HashTable implementation.
It makes it easy to create hashtable objects (otherwise known as Associative Arrays) to store and retrieve key/value pairs quickly.
Hashtables are often used to cache data and can be thought of arrays where the index is a string value instead of an number.
Here I use a hashtable to keep track of the paths we’ve checked and their result.
a MD5 hash implementation.
MD5 is a way to get a somewhat unique fixed-length value from a chunk of data.
It’s a mathematical function that guarantees that a small change in input (say a single bit in the input data) has a large effect on the output value (a totally different number will be generated) and that you can’t reverse the function (you can’t obtain the input just by looking at the output).
It is often used in security applications to transform sensitive data like passwords into unique values that can be (somewhat) safely stored because you can’t easily reverse a md5.
Well, MD5 are not that secure any longer but here we just use their ability to transform our path into a unique number that we can easily use as a filename and a key for our hash to retrieve the current status of the path being checked.
Sample database
Download the PathExistAsync01.zip (67KB) containing the Access 2007 ACCDB database.
Download the PathExistAsync02b.zip (121KB) containing the MDB database1 (untested as I only have Access 2007).
License
Please refer to the source code in the database for the exact licensing terms.
Note that the license only refers to code by me. When code from other sources is used, you will have to conform to their own licensing terms.
This work is licensed under a Creative Commons Attribution 3.0 Unported License.
References
June 20th, 2008
This project provides a custom and enhanced message box replacement for the default MsgBoxfound in Access. A Test database for Access 2007 is available at the bottom of this post. (Updated Tuesday 17MAR2009.)
What’s wrong with the default MsgBox
The default message box in Access is sometimes useful to warn, inform or ask confirmation from the user.
It has, however, a few drawbacks:
- It is bland: the standard message box does not even follow the currently selected Office 2007 scheme.
- The amount of text it can display is limited: if you try to display too much text it will be truncated.
- You can’t copy or save the content of the message.
- Because popup boxes are viewed as intrusive, people tend not to read them and end-up closing message boxes before they realize they may have contained useful information.
- They only displays plain text: you cannot format the message to draw attention to the key points.
- They are blocking, meaning that nothing can happen in the main application while the box is displayed (it can’t even shut down).
Sometimes you need to display an important message or require users to make take a decision.
Message boxes are not to be abused but they serve a useful purpose.
An enhanced message box
Rather than using the bland standard message box you can now have something a bit more customized.
Plain Text version of the enhanced custom message box under the Office Blue Colour Scheme:
RichText version of the enhanced custom message box under the Office Black Colour Scheme:
Here are the features of the enhanced message box:
- It is entirely compatible with the standard one: just change
MsgBox to Box
using find and replace should be enough (see tip below to avoid getting strange errors).
- It allows the user to simply click on a button to copy the content of the message to
the clipboard or save it to a text file to a configurable default location.
- It looks and feels like it belongs to the main application, following its colour scheme.
- It attempts to prevent users from blindly closing the modal box reading the message: buttons will first be inactive for a configurable amount of time. It’s not a perfect solution, but it is quite effective.
- There is a
RichBox version that can display rich HTML content, not just plain text, so important parts of the message can be formatted in a useful way.
- It is able to display large amount of data. While it’s not something you usually want, it may be useful for the message box to display more text in some situations (log or tracing information, legal documentation, etc).
- Rather than sprinkling your code with “
& vbCrLf & _” uglies, you can embed newlines in the text itself by using C-style “\n” escape sequences that will automatically be transformed into the appropriate newlines. Makes for clearer code and less typing.
- Because you get the source, you can easily customise the message box with new icons and colours to better match your overall application’s personality.
- It is non-blocking: if your application forces users to log-off after a certain amount of inactivity, the enhanced message box will just close rather than prevent Access from shutting down like the standard
MsgBox does. Of course, it’s up to you to decide how to handle that gracefully, if at all.
- It properly displays the expected button captions based on the language of the operating system, so it behaves very much like the default
MsgBox (for instance, it will properly display “Cancel” on English systems and “Annuler” on French ones).
- It also properly plays the system sounds associated with the type of message. You can also enable or disable the sound effect as needed.
How to use it
Download the demo below and copy (drag & drop) the following into your application:
- the
FormDialog form,
- the
API_GetTextMetrics module,
- the
Dialog module.
If you rename the FormDialog, make sure you replace any occurrence to it in the code, in particular in the Dialog module.
Since the enhanced message box is just a replacement for the standard one, you just use it like you would use the MsgBox.
There are a few additional settings that can be used to change the behaviour of the enhanced message boxes.
One is that you can adjust the delay before the buttons become activated.
Another one is that you can enable or disable whether beeps should be played or not.
The last settings is the folder where we should save the content of the message when the user clicks the Save button on the message box.
These few settings make the enhanced message box more customizable.
Large text
The standard MsgBox cannot display much text. On the other hand, there is no real limitation to the amount of text the Box and RichBox can display.
When the amount of information is too much to fit the maximum allowed size for the message box the text will overflow and can be scrolled up/down as necessary.
Limitations of the RichBox
The RichBox version relies on the normal TextBox control’s ability under Access 2007 to display RichText wich is nothing more than lightweight HTML.
Because font size may be varying a lot in the message, it becomes very difficult to accurately predict the size of the box needed to display the whole message.
Short of implementing a complete HTML engine, we have to rely on some assumptions to display HTML.
The risk is that sometimes the content may not properly fit the TextBox control in some circumstances.
If you use the RichBox, thoroughly try displaying your messages and tweak the HTML as necessary to include additional lines or non-breaking spaces to ensure that the result looks good.
If you don’t overuse font size and don’t display in multiple fonts the RichBox should do the right thing most of the time.
Don’t overuse the RichBox to display colourful messages. There is a fine line between being informative and tasteless. Keep colours and formatting where it is useful.
I think that in most cases, the plain text version Box is more than enough.
Replacing MsgBox in existing code
As I said above, replacing the standard MsgBox is easy but you need to make sure your search and replace parameters are configured correctly:
If you’re getting strange compile errors, it may be because you forgot to tick the Find Whole Word Only and some of the strings containing the letter sequence “msgbox” were replaced in the process.
If that’s the case, you can revert the damage by simply doing a search and replace across the whole project on:
- VbboxStyle or VbDialog.BoxStyle to be replaced with VbMsgBoxStyle
- VbboxResult or VbDialog.BoxResultto be replaced with VbMsgBoxResult
How it works
The code makes extensive use of Win32 API calls.
Most of the hard work is done in the FomDialog class form. There is too much there to really go into the details but you are welcome to have a look at the commented code.
The code relies also on a utility function from Stephen Lebans used to calculate the size of of text. I have made some minor modification to that code so I would refer you to his original implementation if you are interested in calculating TextBox sizes for forms or reports.
In the code for the FormDialog, I re-implement some of the expected functionalities of the MsgBox: proper arrangement of the buttons, displaying of the appropriate icon, etc.
Once this is done, we calculate the size of the textbox needed to display the whole of the message.
In the case of RichText, we first use Application.PlainText() to convert the HTML into properly formatted plain text. We then calculate the Textbox size using a slightly larger font than needed as a way to ensure that the content of the RichText message will fit the box in most cases.
Once we know the size of the TextBox, we can easily resize the form to properly display the TextBox.
If there is too much text, we resize the form to its maximum permissible (70% or screen width and 90% of screen height) and change some of the visual cues to let the user know the text is overflowing.
One thing of note is the way the form is kept modal.
Rather than using DoCmd.OpenForm and DoCmd.Close I use the form as a class and create an instance manually (see the code in Dialog.Box and Dialog.Richbox). I keep this instance alive until I got the form’s result back.
If you are interested in knowing how the form is made modal, this is the code in FormDialog.ShowModal() what keeps the form open until the user clicks a button:
The Sleep() function is a Win32 API that stops the current process for the given number of milliseconds. This in effects hands back the control to the Operating System for a short time. That way the system is still responsive and does not consume resources when it’s just waiting for user input.
Sample database
You can download a sample database containing all the necessary code as well as a number of tests.
This version only contains the database in Microsoft Access 2007 accdb format.
Download the EnhancedMsgBox01.zip (116KB), v1.3 containing the ACCDB database.
Code Updates
v1.3: 17MAR2009
Thanks to Henry of Access-Pro.de for proposing a correction to the default buttons behaviour.
- Updated behaviour for the default buttons. They are now focused in a way that matches that of the standard msgbox.
- Reversed the naming of the buttons on the form to make it a bit more consistent with the standard box.
v1.2: 07SEP2008
Thanks to Andy Colonna (http://www.pcesoft.com) for uncovering the following bugs (check out his free Spell Checker with source code!):
- Corrected bug in
Form_FormDialog.FilenameSanitize() function that would
fail to remove all invalid characters for a file name.
- File name for the saved text message will be truncated to first 32 characters
of message box title in
Form_FormDialog.MakeFriendlyFileName().
- Changed the use of
FollowHyperlink to ShellExecute to avoid security warning
in some instances in Form_FormDialog.btCopyToFile_Click()
- Corrected twips to pixel conversion bug in
API_GetTextMetrics.fTextWidthOrHeight() that
would result in an improperly sized dialog box when the text message was too
wide.
v1.1: 08AUG2008
- Corrected code for
DefaultButtonDelay (thanks to Geoffrey) (was referencing
wrong variable, causing self-referencing code).
- Corrected code for
Box and RichBox to take the DefaultSavedTextFileFolder
into account (the path was previously not passed onto the dialog boxes and
the text file would always be created in the application folder instead of
the one specified by DefaultSavedTextFileFolder)
- Added license notice at top of source code.
v1.0: 20MAY2008
Resources
This work is licensed under a Creative Commons Attribution 3.0 Unported License.
Free for re-use in any application or tutorial providing clear credit is made about the origin of the code and a link to this site is prominently displayed where end-users can easily access it.
May 20th, 2008
In my previous article about changing the MS Access colour scheme I had the need to allow the user to restart the database after the colour scheme was changed.
(Article and Code Updated 13FEB2009.)
Being able to cleanly restart and compact the application is also useful in other instances:
- Changes made to the environment
- Recovering from errors (for instance after a network disconnection)
- Forcing the user to re-log cleanly into the application
- Automatically restarting a long-running application (for instance so that it may automatically compact on close and restart afresh with or without user intervention).
The problem is that you cannot -to the best of my knowledge- close and open again the same database from within MS Access itself.
Most executables cannot do that and the way to solve the issue is usually to pass the control to another boostrap programme, close the main application and let the bootstrap programme re-open the main application again.
I wanted a simple and clean way of using it. One that would not require shipping external programmes.
How to use it
Download the sample database below, copy the Utilities module or just the Restart sub defined in it into your own application.
To use it, just call the Restart sub and the application will close and re-open.
If you supply the optional Compact:=true parameter, the database will also be compacted during the restart process.
This will work for normal databases (mdb/accdb) and also compiled (mde/accde) and runtime (accdr) databases as well.
Important note
If you want to use this code do not enable the Compact on Close option in Access for your database as the code doesn’t pick that up yet.
Instead, you can either simply call restart Compact:=true on user action (for instance from a menu) or on other triggers, for instance when the database is being open and hasn’t been compacted for more than a week.
How it works
If you’re curious about the technical details, here is how it was put together.
The main idea is that the MS Access database application has to be self-sufficient and restart itself by performing these steps:
- create a small batch file
- run the batch file, passing the path and extension of our database
- close the main application
- the running batch file would wait for the MS Access lock file to be removed
- once the lock file disappears, we open the database after compacting it if required.
The key point here is that the batch file cannot just reopen the database right away: if the application is big or if it’s compacting on close for instance, it may take several seconds to actually close.
The only moment we can be pretty sure that the database is effectively closed is when the lock file is deleted by MS Access.
The batch file is hard-wired in the Restart sub that does all the work:
When the application runs the batch file, it passes 4 arguments:
- the full path to the MSAccess.exe executable (used for compacting the database)
- the full path to the database without the extension
- the database file extension without the leading “.”
- the appropriate database lock file extension (
laccdb or ldb).
This allows us to easily construct the path to either the database or the lock file at line 07 and 09.
Line 08 is actually only inserted if we need to compact the database: it simply launches MSAccess.exe with the /compact command line switch.
The funny use of PING is actually a simple way to wait for some time before we check if the lock file is still there or not. There is not SLEEP or WAIT function provided by default in Windows so we have to be a bit creative and use the time-out option of the PING command trying to ping an inexistent, but valid, IP address.
Once the lock file has disappeared, we open the database at line 09 and then delete the batch file itself so we leave no leftovers.
The other thing of note is that we now use a counter to keep track of the number of times we checked the existence of the lock file.
Once this counter reaches a pre-determined amount (60 by default, ~ 45 seconds) we consider that there is a problem and the database application didn’t close, so we just exit and delete the batch file.
Download the DatabaseRestart.zip (48KB) containing both an Access 2007 ACCDB and Access 2000 MDB test databases.
Other implementations
Code Updates
v1.2: 13FEB2009
- Added optional parameter to compact the database during restart.
v1.1: 09AUG2008
- Now a separate test database (used to be bundled with the Colour Scheme sample).
- Added support for older Access versions (an Access2000 MDB is now included).
- Corrected wrong lock file extension for accd* files.
- Added a time-out feature after which the batch file will delete itself
after a while if the Access lock file wasn’t released
(for instance following a crash).
- Added checks to delete the batch file if it has not deleted itself for some
reason (for instance after a reboot).
- The batch file now has a unique name based on the name of the database,
allowing multiple databases to be restarted from the same directory.
- Added license notice at top of source code.
- Updated the article to reflect the changes.
v1.0: 06MAY2008
This work is licensed under a Creative Commons Attribution 3.0 Unported License.
May 6th, 2008
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