I'm working on an rather small application (C#, winform) that is kind of front-end to MS Access database file stored on shared drive. While it is possible that drive could be down I am checking connection while loading Main Form.
I would like to know your opinions on how to deal with this problem.
I came up with ideas like:
Application shows only MessageBox
with an error message and close
itself (before actually showing up),
as it won't be useful at all.
Application load itself and then
display an error-message to not make
users confused (if they click warning
before reading the explanation).
What are yours best practices?
I think it's rather irrelevant whether the application is shown or not because in the end, you display the message box with the error anyway. The user clicks OK and you close your Application.
However, to me it's a bit nicer without the application showing in background, mainly because it makes no sense to fire it up when the database isn't available. Save yourself (and the pc) the time it takes to show it ;)
Related
I have an access database that has been used for many years, converted from Access 2000 to 2007 and was fine. In the last couple weeks it has been doing strange things!
There is a form for 'editing' a record. When the user clicked on the button to open this form, a small white box appeared and said 'Record Deleted'.
After that, the database was corrupted. I support this database and I can not even get into it in design view. When I try to open it (holding the shift key down while opening it), it takes a while, then it displays the Access design page that has the 'blank database' icon and to the right it lists the frequent opened databases.
So, I can't even get the to objects. The only option I had was to restore from a previous night backup. This meant the users lost all their work for the day. Today, one week later, it has happened again. All the users work was lost because I had to restore from backup.
I don't know where to begin to trouble shoot this since I can not get into it in design view when it has become corrupted. Looking for any suggestions to debug this. I can use a copy of the database I had restored.
Thanks
As a first and most important suggestion. You should split your database.You can do this from the database tools tab on top. By doing this you will have a seperate back end independat of the front end and your client will not loose any data as if they get the error / corrupted database it would not affect the data secured in the backend
Second I havent had the exact same error but in the past I have faced instances where the forms just dont work. a recommendation i read somewhere was to create a new blank form and copy over the elements from this form onto that and delete this form. I doubt if there is any problem with the VBA but it would be worth compiling the code to check.
Apologies if this does not help much, but I hope the first suggestions helps protect your client data in the instance your database crashes.
First, check if any automated VBA code or macro is running on OnOpen, OnLoad, OnCurrent, AfterUpdate, OnDirty, etc. events of the troubleshooting forms. Simply open the VBA window and look at code on the specific form's module. Or in the case of macros, open form in design view and check the Event tab of Property Sheet (and the same for specific buttons, textboxes, etc.). There may be DoCmd.RunCommands occurring when users interact with form controls.
Also, if you find yourself unable to open forms or deal with a corrupted database, consider beginning with a blank Access .accdb file and import all objects from the previous Access 2000 .mdb file. And if specific controls don't function properly, recreate them as needed.
As mentioned above, split your database between BackEnd (only tables) and FrontEnd (forms, queries, macros, modules) which prevents corruption, efficiently runs systems as only data is sent across the network and not whole application items, and overall fosters a better multi-user environment. Each user can have copies of the FE on their local machines but all will connect to one BE on a shared network. To help, Access 2007-2013 has a button for this on the Ribbon under Database Tools.
I've thought of writing a service method that I'd call within the catch block of a try/catch that writes error details to a table for viewing. Then I thought about if the services went down, the client app would have no way of reporting this data. This lead me to the thought of popping up a text box containing the exception details and a Copy button. The user would click the copy button to copy the text and paste it into an email to our support group.
It may sound crude, but I am new to client app development and haven't really given this much thought until now.
Use the Application.DispatcherUnhandledException Event. See this question for a summary (see Drew Noakes answer).
Be aware that there'll be still exceptions which preclude a successful resuming of your application, like after a stack overflow, exhausted memory or lost network connectivity while you're trying to save to the database.
I am currently running a SL3 project where we are in a highly iterative development mode with about 25 active test customers. I am making small changes at a clip of about 4 new builds per day. It is important to know this application is mission critical line of business for these 25 people, it is the tool they use all day to do their work so they are using it constantly and often launch their browser and the app in the morning and never close it until the end of the day.
The challenge is that when I make an update to the application I have no clean way to notify the users, in most cases this is ok as it is rare that I introduce a data contract change or something that would be a classic 'breaking' change to the app/service. Users keep plugging along and will get the change next time they refresh.
Right now we have resorted to emailing everyone and telling them to force refresh or close the browser and log back in.
Surely there is a better way...
Right now my train of thought is to have a method on the server that compares client xap versions and determines if the client being used is the most up to date, if so I will notify the user and make them update.
What have you done to solve this problem?
One way of doing it is to use a push mechanism (I used Kaazing Websoocket Gateway but any would do). When a new version of the XAP is released a message (either manually entered into the system by admin or automated triggered by XAP file change event) would be sent to all the clients. In the simplest scenario some notification would be shown to a user (telling him that a new version is released and the application needs to refresh) and then the app would refresh (by simply reloading the page) saving user's state if necessary.
If I would do this I would just keep it simple. A configuration value in web.config and a corresponding service method that simply returns that value (the value itself could be anything, but a counter is probably wise). Then you could have your Silverlight app poll that service method at regular intervals. Whenever the value changes (which you would do manually when you deploy a new version), just pop up a dialog telling the user to refresh the browser or log in/out. This way you don't have to force them to refresh every time. If you go with the idea of comparing xap file versions they will always be required to refresh, even for non-breaking changes.
If you want to take it further you could come up with some sort of mechanism to distinguish between different severity levels. For instance, if the new config value would contain the string "update_forced", you could force the users to reload the app by logging them out automatically (a little harsh, perhaps). If it contains the string "update_recommended", just show a little icon at the top right corner saying that there is a new version and that they should upgrade in their own time.
Granted, this was targeted at Silverlight 3, but with the PollingDuplex client and such in the newer versions of Silverlight, you could publish an "Update Now" bit to the clients, and build a mechanism in the client to alert the user that there is an update that is now out... that they should update it shortly, etc. You may even be able, through serialization and such, to save the state that they are in when they close the app to reload it.
We've done stuff similar with a LOB app that we built, so that as users are changing things, the rest of the userbase sees those changes immediately. Next up will be putting the flags in to change authorization and upgrades "on the fly" if you will.
What are my options for printing in Silverlight 3? Assume I have this awesome Silverlight application/control that creates a graphical display of some data. Now the user wants to print it.
I have considered a few options but I have yet to test any of these. Before I do that I would like to get some feedback on how it can be done.
Use the browser printing capabilites. In my experience this is does not provide a useful print, but perhaps with some interaction between the Silverlight host and the browser it can be done?
Use WriteableBitmap. The image can either be written locally, but this requires interaction from the user, or sent to the server where a suitable file (e.g. PDF file) can be generated and then sent back to the browser. Unfortunately you now get the overhead of sending the image twice across the network and increased complexity on the server side.
Send XAML back to the server that is then rendered in a WPF application running on the server. The result is the sent back to the client. I'm not sure if this is possible at all however, but if it is the network overhead is less than in option 2. Unfortunately, the complexity on the server side is even higher.
Wait for Silverlight 4?
One thing I have considered is that my awesome control probably will have a ScrollViewer at the highest level, but the user will want to print the entire content of the control, not just whatever is visible inside the bounds of the ScrollViewer. How can I handle this added complexity?
In all seriousness, I think your best option is to wait until Silverlight 4 if your client can wait that long. I've seen a good bit of buzz about SL 4 supporting printing on twitter, though it's not official. I'd wait until PDC in a few weeks and see if any Silverlight bits trickle out to support printing.
Take a look at SmartPrint for Silverlight 3: http://www.smartwebcontrols.com/SmartPrintDetails.aspx
TBH I wouldn't use any of those options:-
Printing from the browser. Fine if you are printing say a chart or something else that scales well on a single sheet of paper. Rubbish for anything else especially where you have scrolled content.
WriteableBitmap. I can't see a client-side only solution being acceptable to the user "Please save this and then print it" message. It could be made to work bouncing off the server but would be bad for bandwidth use (bandwidth is import right? because in a well-connect intranet you wouldn't using Silverlight?).
Sending XAML to server for rendering. Really awkward it would be WPF XAML not SL XAML, where and how would you do the binding, why send XAML at all, since the server needs to be pretty much clued in on this so why can't it hold the XAML needed as well. Or were you thinking of sending just pure XAML with all the data needed? Still its a lot of plumbing needed in the SL that isn't actually related to SL.
Use Silverlight 4, its possible that in the not to distant future this would be the correct no-brainer choice (personally I wouldn't hold my breath) but right now SL4 doesn't exist.
A 5th option
Place report generating code on the server and have the Silverlight app inform the server of the data set required (not necessarily posting the data merely the criteria needed to access the correct set). In my experience direct prints of GUIs aren't particularly satisfactory when the user really needs a good printed form of the data.
Its true that at times the user just wants to quickly get some offline access to a grid of data as it looks there and then. In that situation users often find an export to spreadsheet compatible file preferable to printing, which would be possible from SL.
Something akin to number two is pretty much your best bet and is what I've seen done for printing in most Silverlight apps so far.
You can have the app send content for printing back to the web server (i.e. a new handler or query string parameters to a printing page) and pop up another page for the user to print web content from, or you could allow the user to download a file and have them print that.
Sliverlight 3 does not support printing.
If you can wait for silverlight 4, they have given it "high priority"
If not use Writeablebitmap: http://www.andybeaulieu.com/Home/tabid/67/EntryID/161/Default.aspx
My program is in Flex but it doesn't really matter for the question I am asking. OK say I need to load an XML file for the application to work at all. If I capture an IOError while the xml file is loading, what logically should I do with that? The application needs it or the app is useless, so should I just keep re-trying on error, or should I notify the user to try again later? What would you do?
Thanks.
Ask the user what to do - Retry or Fail, with Fail meaning the app will close . If it makes sense, give the user a chance to browse to the resource.
It really depends on the nature of the file. If you know the file will exist at one time, it may make sense to wait for the file's creation (although this seems like a poor man's network model). However, in situations where an application is useless without a resource, I would fail unrecoverably and give meaningful error messages to the user, as well as log some debugging code to a file that the user could later submit for developer debugging.
Like GMail - do both. Notify the user when an error happens or a timeout is hit, and keep trying in the meantime.
Loading is taking longer than expected, retrying - please wait...
Notify the user that the XML is not available, and offer the user the possibility to retry loading the XML, locate another XML or quit the application.
I don't think you should really try to many times that the page has noticeable lag. It really depends on whether the file being accessed is controlled by a third party or not and whether it is usually failing for large chunks of time or just say a second.