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Hi Pete, Implementing pattern at this stage seems to be bit difficult since most of the functionalities are in place. This specific lock functionality wasn't there and introduced later stages. I presume, it would be nice to introduce some kind of wrapper or attribute in type level which ensure the object level isolation. However, my sincere thanks for your time. Please do update me in case if you sketch something. 
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To be honest - it sounds like you are going to be looking at some amount of "rearchitecting" anyway. Sorry.
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You might use Single Proxy between multiple Users and Rule collection.
Let Proxy decide which user can access which rule object.
Or let there be one Proxy object for each of your Rule object.Each user instead of accesing rule object directly can access Proxy of that rule object and in Proxy you can decide whether to allow user to access the rule object or not.
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It sounds like you are asking how to implement pessimistic locking. There are very simple ways of doing that, although most people agree that it is quite a user-unfriendly thing to do (but sometimes you have no choice).
Basically, create a mutex on the server for the particular rule being edited, and deny edit access to that rule for other users until the mutex is released. The mutex can be anything - for example MS Office products create a file when you open a document for editing, and delete it when you are done.
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Hi Guys,
I have a large, and quite complicated model that i origionaly defined using an object hierachy, but the solution has out grown that.
I require an in memory model that raises events when it is changed. These events can then be handled by any observing controls which in turn can update themselves.
As the model is large, and each control is only interested in one particular part of the Model, i would like to be able to pull out a section of the XML document and observe and apply changes to this block. Idealy i would like to be able to pull an XmlDocument from another XmlDocument and use that, but keeping it synchronised with the parent document.
I am limited to the XmlDocument object due to a .Net 2.0 limitation, although the XDocument (And associated LINQ model) would be perfect for what i am trying to achieve as each node raises change events that bubble up the object hierachy.
Are there any other solutions anyone else can think of?
Cheers
Tris
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Carrier Bags - 21st Century Tumbleweed.
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Tristan Rhodes wrote: I am limited to the XmlDocument object due to a .Net 2.0 limitation
Care to explain that?
led mike
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The application is in .Net 2.0, and the XDocument object is 3.5.
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Carrier Bags - 21st Century Tumbleweed.
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Tristan Rhodes wrote: The application is in .Net 2.0, and the XDocument object is 3.5.
Sure but 2.0 has other things like DataTable and DataSet which do have events?
led mike
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Scratch that.
I'll have a look into it.
Cheers
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Carrier Bags - 21st Century Tumbleweed.
modified on Friday, February 15, 2008 4:41 AM
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Hi Mike,
I don't think DataSets are appropriate to this problem. But i'm not sure what is. I've never encountered anything like this before so my approach may be wrong. I'll try to describe the application and my approach.
1) There is a hierachy of configurations, where a configuration represents a setup for physical goods. The hierachy represents their association.
2) Each configuration contains a block (Tree) of layout data for a visual designer, a block of Aggregates, and a number of other blocks representing various tertiary data tied to the configuration.
3) A number of different controls are bound to the blocks of data for a selected configuration, as well as a number of controls being bound to the hierachy of configuration (From point 1).
4) I am attempting to implement an MVC pattern, where the model would be the XML DOM, the view would be the various controls that are bound to the model, and the controller is the host form (for now) that handles events submitted from the various controls.
5) When the model is changed, i would like to update the views with the changes made. (This is my primary problem). I do not want to re-query the model completely and re-draw the UI when a block is changed, i am only interested in the actual changes made.
6) I require Undo / Redo functionality (Simple enough with an XML Document)
7) Not all displayed data is stored in the model. When the model changes an alternative data source is queried to load Images, Layout data and other values.
It makes me really appreciate how easy web development is when you just re-poll the model and draw a new page / widget.
If you could point me in the right direction with regards to an approach to this problem, it would be greatly appreciated. Alternatively design patterns that are relevant or strategies for solving any of the above issues individually would be just as good.
Cheers
Tris
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Carrier Bags - 21st Century Tumbleweed.
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Not a bad story but you never explain this:
Tristan Rhodes wrote: I don't think DataSets are appropriate to this problem.
If you think it is obvious from your post it's not, at least to me. I have implemented several .NET Desktop applications that use MVC with a DataSet at the core of the Model. In some cases the Data source is an XML file. However in most cases I started out thinking XML files would work and quickly moved on to using the SQL Desktop Database.
Our main .NET Desktop/Web application uses a Database with NHibernate and an Object Model. In my experience and listening to others on the internet talk about managing the session and data layers from a development standpoint, there is no silver bullet, period. You can't just drag and drop controls and handle events to generate a complete solution. If your project data has any level of complexity, and yours certainly does, you will have to do some development. Also IMHO Databases still rule when it comes to managing complex data relationships. If your project is large enough you might want to look into the Castle ActiveRecord implementation[^] which uses NHibernate.
led mike
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Hi Mike,
Thanks for the input. I Can't explain why DataSets are not appropriate, as i'm not sure what concrete reasons i have. I just have a feeling that going down that route would produce bad results, and i've been stung by DataSets before.
In the end, i decided to go with a bog standard XML DOM, and build an API Class(s) that applies transformations, queries the data, and raises application specific events when the DOM changes. I'll just see how it goes.
Cheers
Tris
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Carrier Bags - 21st Century Tumbleweed.
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Tristan Rhodes wrote: I just have a feeling
Some friendly advice. Don't base your technical decisions on your feelings.  Seriously, in todays world the availability of information eliminates the need to make blind decisions that were common years ago and resulted in the mountains of Technical Debt[^] that exist in the industry today.
led mike
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It's past experience as well, and i have looked into it. :P
I love the concept of Code Debt. Spent ages trying to get management to see what it was in my last job, but there's only so much you can teach old school VB heads. ^^
[Edit] And if you say you've never looked at a design or section of code and thought "Something is seriously wrong, but i can't put my finger on it.", i think you lie :P
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Carrier Bags - 21st Century Tumbleweed.
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One word. INotifyPropertyChanged. Have a look at this little puppy - it can be your best friend.
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AHHH!
I wish i knew about that 4 weeks ago 
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Carrier Bags - 21st Century Tumbleweed.
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Tristan Rhodes wrote: I wish i knew about that 4 weeks ago
Sorry. I only just read this thread last night.
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No worries. I don't think that it's suited for the problem i had, but it definitely has some uses is some other stuff i was working on. 
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Carrier Bags - 21st Century Tumbleweed.
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To be honest, I'm having a little trouble picking up the problem domain from this thread. I'm not sure why you need the XML and why you can't use properties.
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Well, i'm trying to route all events through a single root object, only wiring up a hierachy of observable lists, trees and properties to do that will be an absolute nightmare as the model is growing almost daily.
Additionally, i need to be able to run XPath queries on any part of the model and define some kind of schema to validate against. Which i couldn't do with objects.
It's a desktop app if that makes any difference, and the XML would be the state of the solution and everything pretty much revolves around changing that and keeping display parts synchronized with it.
Not sure how to describe it beyond that.
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Carrier Bags - 21st Century Tumbleweed.
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Short of hashing the different observable portions and then periodically checking to see if the hash has changed, tricky. Although if you implemented this with MVC, then it would be less tricky.
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Pete O'Hanlon wrote: INotifyPropertyChanged
That appears to be new in 3.5, yes? I haven't been there yet.
led mike
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It's been around since 2.0.
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Carrier Bags - 21st Century Tumbleweed.
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led mike wrote: That appears to be new in 3.5, yes?
.NET 2.0. I've used it to manage Dirty states in classes - it's rather neat.
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I still can't find the 2.0 Reference to this puppy?[^] 
System.ComponentModel.INotifyPropertyChanged<br />
Finally! Geez, apparently I have been implementing the IAmAnIdiot interface 
Last modified: 45mins after originally posted --
led mike
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