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• Can you use data binding with the Content property of a WPF Frame?

  - by dthrasher

  I can use data binding to set the initial Content of a WPF Frame, but subsequent changes to the the bound property (implemented using INotifyPropertyChange) do not seem to change the content. Also, does anyone know if binding directly to the Content property in this way will cause the bound item to appear in the Frame or NavigationWindow's journal? Some context: I realize that I should probably be using the NavigationService to interact with the Frame, but I'm attempting to follow the MVVM pattern. It seems like it would be much simpler to databind to the Content property...

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• Why implement DB connection pointer object as a reference counting pointer? (C++)

  - by DVK

  At our company one of the core C++ classes (Database connection pointer) is implemented as a reference counting pointer. To be clear, the objects are NOT DB connections themselves, but pointers to a DB connection object. The library is very old, and nobody who designed is around anymore. So far, nether I, nor any C++ experts in the company that I asked have come up with a good reason for why this particular design was chosen. Any ideas? It is introducing some problems (partially due to awful reference pointer implementation used), and I'm trying to understand if this design actually has some deep underlying reasons? The usage pattern these days seems to be that the DB connection pointer object is returned by a DB connection manager class, and it's somewhat unclear whether DB connection pointers were designed to be able to be used independently of DB connection manager.

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• Django "Page not found" error page shows only one of two expected urls

  - by Frank V

  I'm working with Django, admittedly for the first time doing anything real. The URL config looks like the following: urlpatterns = patterns('my_site.core_prototype.views', (r'^newpost/$', 'newPost'), (r'^$', 'NewPostAndDisplayList'), # capture nothing... #more here... - perhaps the perma-links? ) This is in an app's url.py which is loaded from the project's url.py via: urlpatterns = patterns('', # only app for now. (r'^$', include('my_site.core_prototype.urls')), ) The problem is, when I receive a 404 attempting to utilize newpost, the error page only shows the ^$ -- it seems to ignore the newpost pattern... I'm sure the solution is probably stupid-simple but right now I'm missing it. Can someone help get me on the right track...

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• C# event or delegate or other solution?

  - by user295734

  Looking for some help or programmng ideas or mayeb there is some pattern that would help. Have an application that needs to fire alot of events sequentially, it could up to 100 or more unique events, it will be dynamic depeneding on the situation. Trying to find the best practice for doing this. My main idea right now is to create a list of objects iterate thru them, and fire each event. This seems wrong, or bad practice. Or maybe have one object and pass a list or params into one event? Or am I missing some feature in .NET that i could be using or implementing?

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• Close resources before exiting JFrame and TCP communication in Java

  - by Oz Molaim

  1. I'm writing a chat based application on TCP communication. I'm using NetBeans and I want to add functionality to the default EXIT_ON_CLOSE when exiting JFrame. The reason of course is because I want to clean resources and end threads safely. How can I call a method that clear resources and only then close the JFrame safely and end the process. 2. I need to implement the server side. The server has List/HashMap/Queue of 'Socket' with their chat nick-names. Is there any simple design pattern to do it correctly because I don't want to re-invent the wheel. thanks.

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• How can I dynamically inject code into event handlers in Delphi?

  - by mjustin

  For debugging / performance tests I would like to dynamically add logging code to all event handlers of components of a given type. For example, for all Dataset components located ona TDatamodule, I would like to add some code for the BeforeOpen and the AfterOpen event to store the start and end time and send a line to a logger with the elapsed time in the AfterOpen event. I would prefer to do this dynamically (no component subclassing), so that I can add this to all existing datamodules and forms with minimal effort only when needed. Iterating all components and filtering by their type is easy, but for the components which already have event handlers assigned, I need a way to store the existing event handlers, and assign a new modified event handler which first does the logging and then will invoke the original code which was already present. Is there a design pattern which can be applied, or even some example code which shows how to implement this in Delphi?

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• Rails: common approach for handling exceptions in restful actions on objects that have been destroye

  - by Greg

  It is very common in Rails for an objects_controller controller to have RESTful edit and destroy actions like so: def edit @object = Object.find(params[:id]) end def destroy @object = Object.find(params[:id]) @object.destroy redirect_to :back end With an associated view that provides edit and destroy links like so: <%= link_to "Edit the Object", edit_object_path(object) %> <%= link_to "Delete", object, :confirm => 'Are you sure?', :method => :delete %> And it is easy to blow this up. If I open two browser windows, A and B, destroy an object with the "Delete" link in browser A and then press the "Edit" link in browser B, the find() in the edit action throws an exception. Obviously there are several ways to deal with this in the edit action: catch the exception and recover gracefully use @object = find(:first, "conditions... etc. and test the @object before going further But seeing as this is such a common pattern, I would love to know how other folks deal with this situation.

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• Using Regex to remove Carriage Returns in a CSV file in Notepad++

  - by Barry

  I have a CSV file I need to clean up. This is a one-time thing so I'd like to do it in Notepad++ if possible. The CSV file has two fields, one of which is wrapped in quotes. I'd like to remove any Carriage Returns from within the quoted field. I was trying to use this pattern but can't get it quite right... (.*)\"(.*)\n(.*)\"(.*) Also correct me if I am wrong, but I presume the "replace with" value would be something along the lines of: \1\2\3\4 Thanks in advance. I'm also open to alternate solutions such as a quick and dirty PERL script.

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• Can this be done with single SQL query

  - by Ghostrider

  I'm using MySQL. I have a table Type SubType 1 1 1 5 1 6 1 8 2 2 2 3 3 1 3 2 3 3 For each type there is some number of subtypes. For every subtype in a type there is a corresponding subtype in the next type: (1,1) => (2,2) (1,5) => (2,3) (1,6) => (2,2) (1,8) => (2,3) (2,2) => (3,1) (2,3) => (3,2) In case you haven't seen the pattern, here it is: you sort both current and next types by subtype, then in the next type you get subtype in the same position as your current subtype in current type is. If there are more subtypes in the current type that in the next one, you warp around and start from the first subtype in the next type. Is it possible to construct a query that takes current type and subtype and returns corresponding subtype in the next type?

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• Expand in linq not loading inner data collections from service.

  - by Kit

  I am seeing odd behavior with service queries! I am using MVVM pattern for a silverlight 3 app on 3.5 framework and Dataservices 1.5. The following code eager loads correctly the parent object and the child heirarchy perfectly IF and ONLY IF I am preloading the data. But I would like to fetch a different set of the parent object (and its child heirarchy) on different button clicks. What I am seeing is that on button click, only the parent object is retrieved, and the child heirarchy contains nothing. Any suggestions? Any ideas how to tackle this? Thanks all. The method: DataServiceQuery serviceQuery = (DataServiceQuery)(from m1 in dbEntities.gis_Region.Expand("gis_RegionValue/gis_Measure") where m1.RegionGuid == new Guid(regionGuid) select m1); serviceQuery.BeginExecute(GetRegionDetailAsyncResult, serviceQuery); The wired Async Result: DataServiceQuery query = (DataServiceQuery)result.AsyncState; gis_Region region = query.EndExecute(result).First();

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• A PHP object server for business logic

  - by Matthieu

  I wonder if such a thing is possible or even exist : In the MVC pattern, I would like to have the Model part to be persistant in memory, instead of reloading my instances at each execution. So I want only the Controller and View part to be executed. Is there any solution of server that would provide PHP objects (just like a Mysql server provides data records), and that keeps these objects in memory ? A problem would be also : how to have a constructed query to get objects ? Maybe PHP Linq ?

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• Django - Tips to avoid repeating code in views

  - by D Roddis

  I'm moving from a PHP background into Django development via python, mostly for the sake of tackling a MVC (or MVT) that I feel makes the most sense, although in this pattern I've started to notice a lot of repeated code in my views. For example, when logged in I have information regarding the user that I would like to appear on every page, although when using render_to_response and in every view this is required I have to grab the information and pass it to the render_to_response function. I'm wondering what would be the most efficient way to cut down on the duplicate code which would in essence be required in all views in a particular app. Thanks in advance.

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• System.Timers.Timer leaking due to "direct delegate roots"

  - by alimbada

  Apologies for the rather verbose and long-winded post, but this problem's been perplexing me for a few weeks now so I'm posting as much information as I can in order to get this resolved quickly. We have a WPF UserControl which is being loaded by a 3rd party app. The 3rd party app is a presentation application which loads and unloads controls on a schedule defined by an XML file which is downloaded from a server. Our control, when it is loaded into the application makes a web request to a web service and uses the data from the response to display some information. We're using an MVVM architecture for the control. The entry point of the control is a method that is implementing an interface exposed by the main app and this is where the control's configuration is set up. This is also where I set the DataContext of our control to our MainViewModel. The MainViewModel has two other view models as properties and the main UserControl has two child controls. Depending on the data received from the web service, the main UserControl decides which child control to display, e.g. if there is a HTTP error or the data received is not valid, then display child control A, otherwise display child control B. As you'd expect, these two child controls bind two separate view models each of which is a property of MainViewModel. Now child control B (which is displayed when the data is valid) has a RefreshService property/field. RefreshService is an object that is responsible for updating the model in a number of ways and contains 4 System.Timers.Timers; a _modelRefreshTimer a _viewRefreshTimer a _pageSwitchTimer a _retryFeedRetrievalOnErrorTimer (this is only enabled when something goes wrong with retrieving data). I should mention at this point that there are two types of data; the first changes every minute, the second changes every few hours. The controls' configuration decides which type we are using/displaying. If data is of the first type then we update the model quite frequently (every 30 seconds) using the _modelRefreshTimer's events. If the data is of the second type then we update the model after a longer interval. However, the view still needs to be refreshed every 30 seconds as stale data needs to be removed from the view (hence the _viewRefreshTimer). The control also paginates the data so we can see more than we can fit on the display area. This works by breaking the data up into Lists and switching the CurrentPage (which is a List) property of the view model to the right List. This is done by handling the _pageSwitchTimer's Elapsed event. Now the problem My problem is that the control, when removed from the visual tree doesn't dispose of it's timers. This was first noticed when we started getting an unusually high number of requests on the web server end very soon after deploying this control and found that requests were being made at least once a second! We found that the timers were living on and not stopping hours after the control had been removed from view and that the more timers there were the more requests piled up at the web server. My first solution was to implement IDisposable for the RefreshService and do some clean up when the control's UnLoaded event was fired. Within the RefreshServices Dispose method I've set Enabled to false for all the timers, then used the Stop() method on all of them. I've then called Dispose() too and set them to null. None of this worked. After some reading around I found that event handlers may hold references to Timers and prevent them from being disposed and collected. After some more reading and researching I found that the best way around this was to use the Weak Event Pattern. Using this blog and this blog I've managed to work around the shortcomings in the Weak Event pattern. However, none of this solves the problem. Timers are still not being disabled or stopped (let alone disposed) and web requests are continuing to build up. Mem Profiler tells me that "This type has N instances that are directly rooted by a delegate. This can indicate the delegate has not been properly removed" (where N is the number of instances). As far as I can tell though, all listeners of the Elapsed event for the timers are being removed during the cleanup so I can't understand why the timers continue to run. Thanks for reading. Eagerly awaiting your suggestions/comments/solutions (if you got this far :-p)

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• Intersection of sets Mongodb

  - by afvasd

  Hi everyone I am new to mongo, this is my db design: product := { name: str group: ref, comments: [ ref, ref, ref, ref ] } comments := { ... a bunch of comments stuff } tag := { _id: int, #Need this for online requests tag: str, products: [ {product: ref, score: float}, ... ], comments: [ {comment: ref, score: float}, ...], } So my usage pattern is: GIVEN a product, find comments that have certain tag and sort them accordingly. My current approach involves: Look for that tag object that has tag=myTag pull all the comments out, sorted look for that product where product.name=myProduct pull all the comments out (which are dbrefs by the way) loop through the result of 2, and checking if they are in 4, (this I can do a limit 10) etc. It's pretty inefficient. Any better methods?

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• Is ActiveMQ unreliable?

  - by user122991

  Hello, We have been using ActiveMQ 5.2 in our distributed enterprise application for about 3 months. During that time, we have experienced debilitating failures at least twice weekly. In particular, we see: 1) Topic publisher has its connection arbitrarily closed and experiences EOF on attempt to publish. Note well that this issue is not a function of some timeout. It does not correlate reliably with any inactivity. 2) Queue listeners never receive message. Message simply sits on Queue. 2) is much rarer (hardly ever) than 1). In both cases, the failures are highly intermittent-- they cannot be reliably reproduced through any testing usage pattern. Also, there are no errors or warning in the AMQ logs. Have others experienced similar problems? Is there an opinion that some other JMS provider is more reliable? thanks, Joe

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• memristor is a new paradigm (fourth element in integrated circuits)? [closed]

  - by lsalamon

  The memristor will bring a new paradigm of programming, opened enormous opportunities to enable the machines to gain knowledge, creating a new paradigm toward the intelligence altificial. Do you believe that we are paving the way for the era of intelligent machines? More info about : Brain-like systems? "As for the human brain-like characteristics, memristor technology could one day lead to computer systems that can remember and associate patterns in a way similar to how people do. This could be used to substantially improve facial recognition technology or to provide more complex biometric recognition systems that could more effectively restrict access to personal information. These same pattern-matching capabilities could enable appliances that learn from experience and computers that can make decisions." [EDITED] The way is open. News on the subject Brain-Like Computer Closer to Realization

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• When and why will an OS initialise memory to 0xCD, 0xDD, etc. on malloc/free/new/delete?

  - by LeopardSkinPillBoxHat

  I know that the OS will sometimes initialise memory with certain patterns such as 0xCD and 0xDD. What I want to know is when and why this happens. When Is this specific to the compiler used? Do malloc/new and free/delete work in the same way with regard to this? Is it platform specific? Will it occur on other operating systems, such as Linux or VxWorks? Why My understanding is this only occurs in Win32 debug configuration, and it is used to detect memory overruns and to help the compiler catch exceptions. Can you give any practical examples as to how this initialisation is useful? I remember reading something (maybe in Code Complete 2) that it is good to initialise memory to a known pattern when allocating it, and certain patterns will trigger interrupts in Win32 which will result in exceptions showing in the debugger. How portable is this?

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• Recurrance Calendar Issue in Lotus Notes

  - by Preeti

  Hi all, I am creating a Daily Reccurrance pattern in calendar items. But there is a issue as before clicking "save and Send Invitations" button, but in the Document Properties field i am able to view the RepeatForUnit and based on its value i am identifying the Reccurrance type like (D: for daily, W: for Weekly, M: for montlhy etc). But, After clicking on the "save and Send Invitations" button, the Recurrance is getting saved but after that, i am unable to get the RepeatForUnit field in Document Properties. Kindly help me, how to identify the Reccurrance type and the related fields. Note: I am using Domino.dll using C#. Regards, Preeti

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• How to check connection leak using regular expression ?

  - by gauravkarnatak

  I have to check connection leak in my application i.e. open connections which have not been closed. After searching, after I found out that a thousands times connections have been opened but I can't manually go to each and every code fragment and check for connection close thing. I think, it could be possible using a regular expression but the fact is, I am not that well versed with regex that I could write one. Please suggest a regular expression for checking in a no of java files that a opened connection has been closed or not. My code pattern is something like this. try { /* Some code goes here */ con = EJBUtil.getConnection(JNDI_NAME); /* Some code goes here */ } finally { /* Some code goes here */ DBUtil.close(con); or closeConnection.close(con); /* Some code goes here */ }

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• Efficient storage/retrieval method for replayable comet style applications (Google Wave, Etherpad)

  - by Gareth Simpson

  I am considering a web application that would have the same kind of multi user, automatic saving, infinite undo / replay capabilities that you see in Google Wave and Etherpad (albeit on a drastically smaller scale and userbase). Before I go away and reinvent the wheel, is this something that has already been addressed as either a piece of technology or library, or even just a design pattern. I know this isn't necessarily the best Stack Overflow question as there is probably not a "right" answer, but my Google-fu has failed me and I'd just like a reading list! Ordinarily I would be developing under python/django but this is not a firm requirement just a preference :)

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• Zend Framework - Database Table Singleton

  - by Sonny

  I have found myself doing this in my code to 'cache' the work done when instantiating my Zend_Db_Table models: if (Zend_Registry::isRegistered('x_table')) { $x_table = Zend_Registry::get('x_table'); } else { $x_table = new Default_Model_DbTable_X; Zend_Registry::set('x_table', $x_table); } It bothered me that this method isn't very DRY and it dawned on me today that a singleton pattern would probably be a better way to do this. Problem is, I've never written a singleton class. When I did some web searches, I found some offhand comments about Zend_Db_Table singletons, but no real examples. I already have meta-data caching configured. How do I make my Zend_Db_Table models singletons? Are there pitfalls or downsides?

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• Session is Closed! NHibernate shouldn't be trying to grab data

  - by Jeremy Holovacs

  I have a UnitOfWork/Service pattern where I populate my model using NHibernate before sending it to the view. For some reason I still get the YSOD, and I don't understand why the object collection is not already populated. My controller method looks like this: public ActionResult PendingRegistrations() { var model = new PendingRegistrationsModel(); using (var u = GetUnitOfWork()) { model.Registrations = u.UserRegistrations.GetRegistrationsPendingAdminApproval(); } return View(model); } The service/unit of work looks like this: public partial class NHUserRegistrationRepository : IUserRegistrationRepository { public IEnumerable<UserRegistration> GetRegistrationsPendingAdminApproval() { var r = from UserRegistration ur in _Session.Query<UserRegistration>() where ur.Status == AccountRegistrationStatus.PendingAdminReview select ur; NHibernateUtil.Initialize(r); return r; } } What am I doing wrong?

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• Sqlalchemy layout with WSGI application

  - by TheDude

  I'm working on writing a small WSGI application using Bottle and SqlAlchemy and am confused on how the "layout" of my application should be in terms of SqlAlchemy. My confusion is with creating engines and sessions. My understanding is that I should only create one engine with the 'create_engine' method. Should I be creating an engine instance in the global namespace in some sort of singleton pattern and creating sessions based off of it? How have you done this in your projects? Any insight would be appreciated. The examples in the documentation dont seem to make this entirely clear (unless I'm missing something obvious). Any thoughts?

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• VB.net: Custom ' TODO: List on an Interface

  - by Shiftbit

  How do I add my own todo and comments list to appear on Interfaces? I want it to pop up like IDisposable does: Public Class Foo : Implements IDisposable Private disposedValue As Boolean = False ' To detect redundant calls ' IDisposable Protected Overridable Sub Dispose(ByVal disposing As Boolean) If Not Me.disposedValue Then If disposing Then ' TODO: free other state (managed objects). End If ' TODO: free your own state (unmanaged objects). ' TODO: set large fields to null. End If Me.disposedValue = True End Sub #Region " IDisposable Support " ' This code added by Visual Basic to correctly implement the disposable pattern. Public Sub Dispose() Implements IDisposable.Dispose ' Do not change this code. Put cleanup code in Dispose(ByVal disposing As Boolean) above. Dispose(True) GC.SuppressFinalize(Me) End Sub #End Region End Class Whenever I enter my own comments and todo list they are never autogenerated like IDisposable Interface does. I would like my own Interfaces to preserve the comments so that I can share my Interfaces with in source documentation.

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• GridView items are displaying the wrong drawables sometimes.

  - by originalbryan

  I've implemented a GridView based on this tutorial. It works great unless open up the search dialog or rotate the screen then scroll around. When the search dialog and virtual keyboard appear, the drawables for each of my grid items shift. I can click on them and they do what I expect, except the drawable is wrong. The same problem happens when I go into landscape mode and scroll around. If I scroll down, up, the down again, the drawables are shuffled. For better illustration, let's say I have three objects, each with an image. Obj A shows an Apple Obj B shows a Banana Obj C shows a Cantaloupe When the shift occurs I end up with: Obj A shows an Cantaloupe Obj B shows a Banana Obj C shows a Apple The problem isn't consistent between the two causes (search dialog and screen rotate n' scroll), but each cause itself is consistent. Scrolling around repeatedly reveals a pattern as does the search dialog appearing. How can I stop this from happening?

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