I have an application that will be running on several desktop computers simultaneously (It will stay open 24/7). At midnight, Data will be copied from one table to another. Since my program will be open on several different machines, it will attempt to make this transaction multiple times which could cause loss of data. How do I centralize my code where this event will occur only one time? Any help will be greatly appreciated. I have several ideas as to how I could do this by scheduling a task on windows using a small app I made; however, my desire is to include the code to "copy the tables" in the application itself. Thanks.
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I created a time recording program in vb.net with a sql-server as backend. User can send there time entries into the database (i used typed datasets functionality) and send different queries to get overviews over there working time.
My plan was to put that exe in a folder in our network and let the user make a link on their desktops. Every user writes into the same table but can only see his own entries so there is no possibility that two user manipulate the same dataset.
During my research i found a warning that "write contentions between the different users" can be occur. Is that so in my case?
Has anyone experience with "many user using the same exe" and where that is using datasets and could give me an advice whether it is working or what i should do instead?
SQL Server will handle all of your multi-user DB access concerns.
Multiple users accessing the same exe from a network location can work but it's kind of a hack. Let's say you wanted to update that exe with a few bug fixes. You would have to ensure that all users close the application before you could release the update. To answer you question though, the application will be isolated to each user running it. You won't have any contention issues when it comes to CRUD operations on the database due to the network deployment.
You might consider something other than a copy/paste style publishing of your application. Visual Studio has a few simple tools you can use to publish your application to a central location using ClickOnce deployment.
http://msdn.microsoft.com/en-us/library/31kztyey(v=vs.110).aspx
My solution was to add a simple shutdown-timer in the form, which alerts users to saving their data before the program close att 4 AM.
If i need to upgrade, i just replace the .exe on the network.
Ugly and dirty, yes... but worked like a charm for the past 2 years.
good luck!
I have a Windows forms application which I have a bit of a sporadic issue with. The application would randomly start/spawn another instance of itself without any warning or reason. I only have one use of Process.Start in the whole application (15 forms/files and about 5000 lines of code) and that calls a net use command to map a network drive.
I've not been able to reproduce this in my testing and therefore I made the project a Windows Assembly Framework single instance application (pros/cons of this I know). This has obviously stopped any other instances of the application from running, but now at random intervals their program will minimise and snap to another application they have running. I don't know for certain whether this is related but they certainly sound a bit close for comfort!
Any ideas/pointers/thoughts appreciated.
Thanks,
Jamie
This could happen if the application, at some point, calls Application.Restart.
I'm doing a db in access 2002 and I've had some problems with the locking shared mode. I have an app that has a lot of programs and almost 10 users logged on. And one of things that the app do is open a report, that user choose the program and the number (usually has 4 numbers for each program), and before the report open, I open it in hidden mode and I edit the report for current program/number, with this rotine I just have one report that may turn in hundreds... saving memory and optimizing it. Then I save it and open it again in view mode.
But the problem is when has other person using the app, so the access can't edit and save report... just in exclusive mode!
Has a cmd in vba to allow momentarily changes in shared mode? I don't know, like freeze all user, save and then unfreeze them?
Or any other suggestion?
About create a Front-End/Back-End I think that is impracticable, cause is a beta version and I have to update it often and I already tried to do this also, but it's became too slow... I splitted then in a database(just tables) into network and front-end with all querys, forms, reports and linked tables in local PC, but it really became tooo slow. If someone can help me let it faster would solve my problems too
I splitted the db and I'm trying optimize it. I read a lot about it on the web and I changed all Access setting that I saw that need to be changed and now I get a faster program. But slower than with a single app.
But now there are just fell Forms that making my app slow.
For example I have some Forms that always when I close it I spends a long time waiting it to close ;(
So I realised that this Forms are always saving before close. And always that a form need to save(with linked tables taht are in the network) waste a lot of time, so I need to avoid this.
But I didn't get it so far...
I realise that this forms are saving because in form_open I hidde some columns(that are different for each program) and edit it caption. And then if I need to close form, it saves and waste this such time!
How could I hidde/edit this columns withou need to save form? Or how could I close form without save structure changes?
I know how to do that with just a button, but these forms are datasheets and I can close it only in "X" Form button. And unfortunattely Access dont have BeforeClose event, and in a OnClose event it save before go to this sub!
See if you can make use of a WhereCondition with the DoCmd.OpenReport Method to avoid the need to modify your report's design at run time.
The WhereCondition is applied to your report's existing record source query as if it where written into that query's WHERE clause.
So if the record source for YourReport is ...
SELECT program_id, some_number, another_field
FROM YourTable;
... then this ...
DoCmd.OpenReport "YourReport", _
WhereCondition:="program_id = 7 AND some_number = 22"
would give you the same set of rows as would revising the record source to this ...
SELECT program_id, some_number, another_field
FROM YourTable
WHERE
program_id = 7
AND some_number = 22;
This advantage of this approach, if you can make it work for your situation, is that you would no longer need exclusive access to the db since you're not actually changing the report's design.
The related issue about beta status making it impractical to split the application is something you should re-consider carefully. Splitting ensures you can easily preserve the data in the BE when you roll out changes to the FE application. Even if you've come up with another method to avoid losing data when you change versions, that method can not be simpler than segregating the data into a BE file.
And when you split the application, each user should get their own copy of the FE file which is stored locally on their machine's hard drive; those FE files will contain links to the tables in the BE file which is stored on a file share.
Keeping the users' FE applications updated as you release new versions is a problem which has been solved. For example, see Tony Toews' Auto FE Updater. And you can find other approaches by searching the web.
If your concern is performance with a split application, check Tony's Microsoft Access Performance FAQ.
I have a small VB .Net application that, among other things, attempts to substitute system wide typed text by the user(hotstrings concept). To achieve that, I have deployed 'ahk2exe' and 'AutoHotkeySC.bin' with my application and did the following:
When a user assignes a new 'hotstring':
Kill 'hotstring' exe script file if running
Append new hotstring to the script file (if non exist then create a new one)
Convert edited/new script file to exe (using ahk2exe)
Run the newly converted script exe
(somewhere there I also check if the hotstring has been already assigned)
However, I am not totally satisfied with this method for the following two main reasons:
The extra resources deployed with the application.
Lag: The time it takes for the system to kill the process and then restart it takes a minimum of 5 seconds on my fast computer and more on other computers. That amount of time is much more than the time it takes the user to assign the hotstring, minimize/close the window and then test his/her new hotstring. When the user does so initially with no success they will think the process failed. So this method is not very good for user experience.
So, I am looking for a different method or implementation. May be using keyboard hooks? Or maybe adding a .dll library that achieves the same. Are there any resources you know about that might help (free or commercial)? What is the best way to achieve my desired goal?
Many thanks for your help.
Implementing what Autohotkey does would be a pretty non trivial task.
But I'm pretty sure that AHK supports an "autoreload" option for scripts
googling "autohotkey auto reload" turned up several pages discussing that very concept. IF that worked, all you'd have to do is update the script file and that's it, AHK should automatically reload the script.
I've created a small application that basically reads and writes to a single Excel.exe process. It's basically a timer that records the time I use on projects and then store it in an Excel sheet. This works great, however, I've noticed that if I open Excel manually, work on some sheets and whatnot, save and exit etcetc, the process my software use gets broken or something. The same thing that happens if I manually close the excel.exe process and my software doesn't "know".
So I was wondering if it's possible to protect the excel.exe process somehow? To make sure it can't be closed or tampered with in the meantime?
Let me suggest an alternative approach that does not require you to have an Excel process running all the time (after all, this also consumes a lot of system resources):
Let your application record your information. Every now and then -- for example, after a work entry has been finished or a specific time has elapsed -- open the Excel sheet, write the data, and close it again (also closing the Excel process that you are automating). This save operation should not take more than a few seconds and it will (mostly) prevent the problem you are experiencing.
In fact, since Office automation is always a bit painful, an even better way would be to output your data without requiring an Excel process. To do this, you could use
one of the third-party Excel libraries available for .net,
a CSV or HTML file, which can be opened by Excel, or
open the Excel file as a database with ADO.NET.
You cannot protect a process, but you can check the process.HasExited property to find out whether the process has terminated and take action based on that.
Add an exception handler. Either call non-throw methods if possible.