Hi,
My website has a setup whereby when the application starts a module called SiteContent is "created". This runs a clearup function which basically deletes any irrelevant data from the database, in case any has been left in there from previously run functions.
The module has instances of Manager classes - namely RangeManager, CollectionManager, DesignManager. There are others but I will just use these as an example. Each Manager class contains an array of items - items may be of type Range, Collection or Design, whichever one is relevant. Data for each range is then read into an instance of Range, Collection or Design. I know this is basically duplicating data - not very efficient but its my final year project at the moment so I can always change it to use Linq or something similar later, when I am not pressured by the one month deadline.
I have a form which, on clicking the Save button, saves data by calling SiteContent.RangeManager.Create(vars) or SiteContent.RangeManager.Update(Range As Range, vars) (or the equivalent for other manager classes, whichever one happens to be relevant).
These functions call a stored procedure to insert or update in the relevant table.
Classes Range, Collection and Design all have attributes such as Name, Description, Display and several others. When the Create or Update function is called, the Manager loops through all the other items to check if an item with the same name already exists. The Update function ensures that it does not compare the item being updated to itself. A custom exception (ItemAlreadyExistsException) is thrown if another item with the same name is found.
For some weird reason, if I go into a Range, Collection or Design in edit mode, change something and try to update it, it occasionally doesnt update the item. When I say occasionally I mean every 3 - 4 page loads, sometimes more. I see absolutely no pattern in when or why it occurs. I have a try-catch statement which catches ItemAlreadyExistsException, and outputs "An item with this name already exists" when caught. Occasionally it will output this; other times it will not.
Does anyone have any idea why this could happen? Maybe a mistake which someone has made and solved before?
I used to have regular expressions in place that the names were compared to - I believe it was [a-zA-Z]{1, 100} (between 1 and 100 lower- or upper-case characters). For some reason the customer who I am developing the site for used to get errors saying its not in the correct format. Yet he could try the same text 5 minutes later and it would work fine. I am thinking this could well be the same problem, since both problems occur at random.
Many thanks in advance.
Regards,
Richard Clarke
Edit: After much time spent narrowing down the code, I have decided to wait till my brother, who has been a programmer for at least 8 years more than I have, to come down over Easter and get him to have a look at it. If he cant solve it then I will zip the files up and put them somewhere for people to access and have a go at.
I narrowed it down literally to the minimum number of files possible, and it still occurs. It seems to be about every 10th time. Having said that, I force the manager classes to refresh every 10 page loads or 5 minutes (whichever one is sooner). I may look into this - this could be causing a problem. Basically each Manager contains an array of an object. This array is populated using data from the database. The Update function takes an instance of the item and the new values to be set for the object. If it happens to be a page load where the array is reset (ie the data is loaded freshly from the database) then the object instance with the same ID wont be the same instance as the one being passed in. This explains the fact that it throws an ItemAlreadyExistsException now and then. It all makes sense now the more I think about it. If I were to pass in the ID of the object to be altered, rather than the object itself, then it should work perfectly. I will answer the question if I solve it..