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  • *UPDATED* help with django and accented characters?

    - by Asinox
    Hi guys, i have a problem with my accented characters, Django admin save my data without encoding to something like "&aacute;" Example: if im trying a word like " Canción ", i would like to save in this way: Canci&oacute;n, and not Canción. im usign Sociable app: {% load sociable_tags %} {% get_sociable Facebook TwitThis Google MySpace del.icio.us YahooBuzz Live as sociable_links with url=object.get_absolute_url title=object.titulo %} {% for link in sociable_links %} <a href="{{ link.link }}"><img alt="{{ link.site }}" title="{{ link.site }}" src="{{ link.image }}" /></a> {% endfor %} But im getting error if my object.titulo (title of the article) have a accented word. aught KeyError while rendering: u'\xfa' Any idea ? i had in my SETTING: DEFAULT_CHARSET = 'utf-8' i had in my mysql database: utf8_general_ci COMPLETED ERROR: Traceback: File "C:\wamp\bin\Python26\lib\site-packages\django\core\handlers\base.py" in get_response 100. response = callback(request, *callback_args, **callback_kwargs) File "C:\wamp\bin\Python26\lib\site-packages\django\views\generic\date_based.py" in object_detail 366. response = HttpResponse(t.render(c), mimetype=mimetype) File "C:\wamp\bin\Python26\lib\site-packages\django\template\__init__.py" in render 173. return self._render(context) File "C:\wamp\bin\Python26\lib\site-packages\django\template\__init__.py" in _render 167. return self.nodelist.render(context) File "C:\wamp\bin\Python26\lib\site-packages\django\template\__init__.py" in render 796. bits.append(self.render_node(node, context)) File "C:\wamp\bin\Python26\lib\site-packages\django\template\debug.py" in render_node 72. result = node.render(context) File "C:\wamp\bin\Python26\lib\site-packages\django\template\loader_tags.py" in render 125. return compiled_parent._render(context) File "C:\wamp\bin\Python26\lib\site-packages\django\template\__init__.py" in _render 167. return self.nodelist.render(context) File "C:\wamp\bin\Python26\lib\site-packages\django\template\__init__.py" in render 796. bits.append(self.render_node(node, context)) File "C:\wamp\bin\Python26\lib\site-packages\django\template\debug.py" in render_node 72. result = node.render(context) File "C:\wamp\bin\Python26\lib\site-packages\django\template\loader_tags.py" in render 62. result = block.nodelist.render(context) File "C:\wamp\bin\Python26\lib\site-packages\django\template\__init__.py" in render 796. bits.append(self.render_node(node, context)) File "C:\wamp\bin\Python26\lib\site-packages\django\template\debug.py" in render_node 72. result = node.render(context) File "C:\wamp\bin\Python26\lib\site-packages\sociable\templatetags\sociable_tags.py" in render 37. 'link': sociable.genlink(site, **self.values), File "C:\wamp\bin\Python26\lib\site-packages\sociable\sociable.py" in genlink 20. values['title'] = quote_plus(kwargs['title']) File "C:\wamp\bin\Python26\lib\urllib.py" in quote_plus 1228. s = quote(s, safe + ' ') File "C:\wamp\bin\Python26\lib\urllib.py" in quote 1222. res = map(safe_map.__getitem__, s) Exception Type: TemplateSyntaxError at /noticia/2010/jun/10/matan-domingo-paquete-en-la-avenida-san-vicente-de-paul/ Exception Value: Caught KeyError while rendering: u'\xfa' thanks, sorry with my English

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  • Revisiting .NET, but what should I focus on?

    - by Wayne M
    After about a two-year hiatus, I'm brushing up on my .NET skills to find a .NET job (my previous two positions have very little development, or development using legacy technologies, so apart from a few very minor apps I have not touched .NET in close to two years). I'm aware of things like ASP.NET MVC, and I have previously read on things like NHibernate and DI/IOC, albeit I have yet to use them apart from very trivial "Hello World" type applications. I have a subscription to Rob Conery's Tekpub website and occasionally watch these videos when I have free time. My concern is this: I don't live in a very technical area. I would be surprised if any but the most tech-savvy companies have heard of, let alone use, ASP.NET MVC, NHibernate (or even LINQ/EF), or know about IoC. I would be willing to bet a large sum of money that 95% of the possible jobs I could obtain will use the following: Visual Source Safe, if any VCS at all ASP.NET 2.0 Webforms (3.5 if lucky) Raw ADO.NET on top of a very thin implementation of the Gateway pattern Stored Procedures in the database for most CRUD operations Gratuitous use of code-behind, with a Service layer if I'm lucky If I were extremely lucky, I might find a shop that has heard of ORMs and either uses one, or has wrote their own data abstraction. Also if I were lucky, the company would be using Model-View-Presenter. In light of this I'm not sure what I should focus on learning. Personally, I would prefer to be using the latest stuff - ASP.NET MVC, NHibernate, jQuery, WCF etc. Reality says I should go back to the basics, since it looks like most potential opportunities aren't going to be anywhere near the cutting edge, or anywhere close to it. And, as much as I would like to find a position and start to show the other developers the benefits, in my past experience this has usually resulted in my being fired for "not being a team player" and doing things the bad old way. So, I am curious how you would approach a situation like this? What should I focus on, in order to A) Reaquaint myself with .NET, and B) Prepare myself to obtain a .NET job again that is more than likely going to use techniques that I and most other knowledgeable developers will scoff at?

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  • SIFR 3.0 - Font Size

    - by Nick
    I have been working with SIFR 3.0 for some time now and the font-size never seems to work correctly. I understand the most basic concepts behind SIFR. SIFR runs when you load the page. It does some calculations one the size of the HTML rendered font and then replaces it with a flash movie that is roughly equal to that size. Because of this, you want to style your HTML font to match the size of your SIFR font as close as possible. My problem always comes up when trying to style these two font sizes to match. Let's say I want to use a SIFR font of Helvetica Neue Lt at about 32px. The HTML equivalent is something like Arial Narrow at about 36px with some negative letter spacing. So here is what I do. In sifr.css I'll write: @media screen { .sIFR-active h1 { visibility: hidden; z-index: 0 !important; font-size: 36px; } } Great, that gets the default HTML font the size I need. Now I need to update the flash SIFR font size. So I go into sifr-config.js and write something like this: sIFR.replace(HelveticaNeueThinCond, { selector: 'h1', css: '.sIFR-root { color: #762123; font-size: 32px; line-height: 1em; }', transparent: true }); So right now everything is working great. That is until my h1 text wraps more than one line. For some reason, when the text wraps it only shows the first line. It seems calculates the height wrong. This is very weird because I ran some tests. I took "visibility: hidden" off of "sIFR-active h1" to make sure that the HTML rendered text was the right size. It is, it takes up two lines. However, when the Flash replaces this text it gives it a min-height of one line of text. Odd. The only way I could find to fix this wrapping problem was to remove "font-size: 32px;" from "sIFR.replace(HelveticaNeueThinCond" in sifr-config. The problem I run into then is that it inherits the font-size set in sifr.css. Now the problem is that my HTML text is bigger then the SIFR text. So occasional my HTML text will wrap to a new line before my SIFR text leaving a big white space. So, how do I set two different font-size (one for my HTML text and one for my SIFR) without losing the wrapping. The only time I have been able to use the successfully is when I have a SIFR font that is so similar to a web safe font that they can share the same font-size attribute. Thanks

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  • Synchronized Enumerator in C#

    - by Dan Bryant
    I'm putting together a custom SynchronizedCollection<T> class so that I can have a synchronized Observable collection for my WPF application. The synchronization is provided via a ReaderWriterLockSlim, which, for the most part, has been easy to apply. The case I'm having trouble with is how to provide thread-safe enumeration of the collection. I've created a custom IEnumerator<T> nested class that looks like this: private class SynchronizedEnumerator : IEnumerator<T> { private SynchronizedCollection<T> _collection; private int _currentIndex; internal SynchronizedEnumerator(SynchronizedCollection<T> collection) { _collection = collection; _collection._lock.EnterReadLock(); _currentIndex = -1; } #region IEnumerator<T> Members public T Current { get; private set;} #endregion #region IDisposable Members public void Dispose() { var collection = _collection; if (collection != null) collection._lock.ExitReadLock(); _collection = null; } #endregion #region IEnumerator Members object System.Collections.IEnumerator.Current { get { return Current; } } public bool MoveNext() { var collection = _collection; if (collection == null) throw new ObjectDisposedException("SynchronizedEnumerator"); _currentIndex++; if (_currentIndex >= collection.Count) { Current = default(T); return false; } Current = collection[_currentIndex]; return true; } public void Reset() { if (_collection == null) throw new ObjectDisposedException("SynchronizedEnumerator"); _currentIndex = -1; Current = default(T); } #endregion } My concern, however, is that if the Enumerator is not Disposed, the lock will never be released. In most use cases, this is not a problem, as foreach should properly call Dispose. It could be a problem, however, if a consumer retrieves an explicit Enumerator instance. Is my only option to document the class with a caveat implementer reminding the consumer to call Dispose if using the Enumerator explicitly or is there a way to safely release the lock during finalization? I'm thinking not, since the finalizer doesn't even run on the same thread, but I was curious if there other ways to improve this.

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  • Entity Attribute Value Database vs. strict Relational Model Ecommerce question

    - by Dr. Zim
    It is safe to say that the EAV/CR database model is bad. That said, Question: What database model, technique, or pattern should be used to deal with "classes" of attributes describing e-commerce products which can be changed at run time? In a good E-commerce database, you will store classes of options (like TV resolution then have a resolution for each TV, but the next product may not be a TV and not have "TV resolution"). How do you store them, search efficiently, and allow your users to setup product types with variable fields describing their products? If the search engine finds that customers typically search for TVs based on console depth, you could add console depth to your fields, then add a single depth for each tv product type at run time. There is a nice common feature among good e-commerce apps where they show a set of products, then have "drill down" side menus where you can see "TV Resolution" as a header, and the top five most common TV Resolutions for the found set. You click one and it only shows TVs of that resolution, allowing you to further drill down by selecting other categories on the side menu. These options would be the dynamic product attributes added at run time. Further discussion: So long story short, are there any links out on the Internet or model descriptions that could "academically" fix the following setup? I thank Noel Kennedy for suggesting a category table, but the need may be greater than that. I describe it a different way below, trying to highlight the significance. I may need a viewpoint correction to solve the problem, or I may need to go deeper in to the EAV/CR. Love the positive response to the EAV/CR model. My fellow developers all say what Jeffrey Kemp touched on below: "new entities must be modeled and designed by a professional" (taken out of context, read his response below). The problem is: entities add and remove attributes weekly (search keywords dictate future attributes) new entities arrive weekly (products are assembled from parts) old entities go away weekly (archived, less popular, seasonal) The customer wants to add attributes to the products for two reasons: department / keyword search / comparison chart between like products consumer product configuration before checkout The attributes must have significance, not just a keyword search. If they want to compare all cakes that have a "whipped cream frosting", they can click cakes, click birthday theme, click whipped cream frosting, then check all cakes that are interesting knowing they all have whipped cream frosting. This is not specific to cakes, just an example.

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  • Subversion vision and roadmap

    - by gbjbaanb
    Recently C Michael Pilato of the core subversion team posted a mail to the subversion dev mailing list suggesting a vision and roadmap for the future of Subversion. Naturally, he wanted as much feedback and response as possible which is why I'm posting this here - to elicit some suggestions and contributions from you, the users of Subversion. Any comments are welcome, and I shall feedback a synopsis with a link to this question to the dev mailing list. Similarly, I've created a post on ServerFault to get feedback from the administator side of things too. So, without further ado: Vision The first thing on his "vision statement" is: Subversion has no future as a DVCS tool. Let's just get that out there. At least two very successful such tools exist already, and to squeeze another horse into that race would be a poor investment of energy and talent. There's no need to suggest distributed features for subversion. If you want a DVCS, there should be no ill-feeling if you migrate to Git, Mercurial or Bazaar. As he says, its pointless trying to make SVN like them when they already exist, especially when there are different usage patterns that SVN should be targetting. The vision for Subversion is: Subversion exists to be universally recognized and adopted as an open-source, centralized version control system characterized by its reliability as a safe haven for valuable data; the simplicity of its model and usage; and its ability to support the needs of a wide variety of users and projects, from individuals to large-scale enterprise operations. Roadmap Several ideas were suggested as being "very nice to have" and are offered as the starting point of a future roadmap. These are: Obliterate Shelve/Checkpoint Repository-dictated Configuration Rename Tracking Improved Merging Improved Tree Conflict Handling Enterprise Authentication Mechanisms Forward History Searching Log Message Templates If anyone has suggestions to add, or comments on these, the subversion community would welcome all of them. Community And lastly, there was a call for more people to become involved with Subversion development. As with most OSS projects it can be daunting to join, but there is now a push for more to be done to help. If you feel like you can contribute, please do so.

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  • Sockets server design advice

    - by Rob
    We are writing a socket server in c# and need some advice on the design. Background: Clients (from mobile devices) connect to our server app and we leave their socket open so we can send data back down to them whenever we need to. The amount of data varies but we generally send/receive data from each client every few seconds, so it's quite intensive. The amount of simultaneous connections can range from 50-500 (and more in the future). We have already written a server app using async sockets and it works, however we've come across some stumbling blocks and we need to make sure that what we're doing is correct. We have a collection which holds our client states (we have no socket/connection pool at the moment, should we?). Each time a client connects we create a socket and then wait for them to send us some data and in receiveCallBack we add their clientstate object to our connections dictionary (once we have verified who they are). When a client object then signs off we shutdown their socket and then close it as well as remove them from our collection of clients dictionary. Presumably everything happens in the right order, everything works as expected. However, almost everyday it stops accepting connections, or so we think, either that or it connects but doesn't actually do anything past that and we can't work out why it's just stopping. There are few things that we'r'e unsure about 1) Should we be creating some kind of connection pool as opposed to just a dictionary of client sockets 2) What happens to the sockets that connect but then don't get added to our dictionary, they just linger around in memory doing nothing, should we create ANOTHER dictionary that holds the sockets as soon as they are created? 3) What's the best way of finding if clients are no longer connected? We've read some many methods but we're not sure of the best one to use, send data or read data, if so how? 4) If we loop through the connections dictonary to check for disposed clients, should we be locking the dictionary, if so how does this affect other clients objects trying to use it at the same time, will it throw an error or just wait? 5) We often get disposedSocketException within ReceiveCallBack method at random times, does this mean we are safe to remove that socket from the collection? We can't seem to find any production type examples which show any of this working. Any advice would be greatly received

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  • Global Entity Framework Context in WPF Application

    - by OffApps Cory
    Good day, I am in the middle of development of a WPF application that is using Entity Framework (.NET 3.5). It accesses the entities in several places throughout. I am worried about consistency throughout the application in regard to the entities. Should I be instancing separate contexts in my different views, or should I (and is a a good way to do this) instance a single context that can be accessed globally? For instance, my entity model has three sections, Shipments (with child packages and further child contents), Companies/Contacts (with child addresses and telephones), and disk specs. The Shipments and EditShipment views access the DiskSpecs, and the OptionsView manages the DiskSpecs (Create, Edit, Delete). If I edit a DiskSpec, I have to have something in the ShipmentsView to retrieve the latest specs if I have separate contexts right? If it is safe to have one overall context from which the rest of the app retrieves it's objects, then I imagine that is the way to go. If so, where would that instance be put? I am using VB.NET, but I can translate from C# pretty good. Any help would be appreciated. I just don't want one of those applications where the user has to hit reload a dozen times in different parts of the app to get the new data. Update: OK so I have changed my app as follows: All contexts are created in Using Blocks to dispose of them after they are no longer needed. When loaded, all entities are detatched from context before it is disposed. A new property in the MainViewModel (ContextUpdated) raises an event that all of the other ViewModels subscribe to which runs that ViewModels RefreshEntities method. After implementing this, I started getting errors saying that an entity can only be referenced by one ChangeTracker at a time. Since I could not figure out which context was still referencing the entity (shouldn't be any context right?) I cast the object as IEntityWithChangeTracker, and set SetChangeTracker to nothing (Null). This has let to the current problem: When I Null the changeTracker on the Entity, and then attach it to a context, it loses it's changed state and does not get updated to the database. However if I do not null the change tracker, I can't attach. I have my own change tracking code, so that is not a problem. My new question is, how are you supposed to do this. A good example Entity query and entity save code snipped would go a long way, cause I am beating my head in trying to get what I once thought was a simple transaction to work. Any help would elevate you to near god-hood.

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  • Asynchronous subprocess on Windows

    - by Stigma
    First of all, the overall problem I am solving is a bit more complicated than I am showing here, so please do not tell me 'use threads with blocking' as it would not solve my actual situation without a fair, FAIR bit of rewriting and refactoring. I have several applications which are not mine to modify, which take data from stdin and poop it out on stdout after doing their magic. My task is to chain several of these programs. Problem is, sometimes they choke, and as such I need to track their progress which is outputted on STDERR. pA = subprocess.Popen(CommandA, shell=False, stdout=subprocess.PIPE, stderr=subprocess.PIPE) # ... some more processes make up the chain, but that is irrelevant to the problem pB = subprocess.Popen(CommandB, shell=False, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=pA.stdout ) Now, reading directly through pA.stdout.readline() and pB.stdout.readline(), or the plain read() functions, is a blocking matter. Since different applications output in different paces and different formats, blocking is not an option. (And as I wrote above, threading is not an option unless at a last, last resort.) pA.communicate() is deadlock safe, but since I need the information live, that is not an option either. Thus google brought me to this asynchronous subprocess snippet on ActiveState. All good at first, until I implement it. Comparing the cmd.exe output of pA.exe | pB.exe, ignoring the fact both output to the same window making for a mess, I see very instantaneous updates. However, I implement the same thing using the above snippet and the read_some() function declared there, and it takes over 10 seconds to notify updates of a single pipe. But when it does, it has updates leading all the way upto 40% progress, for example. Thus I do some more research, and see numerous subjects concerning PeekNamedPipe, anonymous handles, and returning 0 bytes available even though there is information available in the pipe. As the subject has proven quite a bit beyond my expertise to fix or code around, I come to Stack Overflow to look for guidance. :) My platform is W7 64-bit with Python 2.6, the applications are 32-bit in case it matters, and compatibility with Unix is not a concern. I can even deal with a full ctypes or pywin32 solution that subverts subprocess entirely if it is the only solution, as long as I can read from every stderr pipe asynchronously with immediate performance and no deadlocks. :)

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  • Succinct introduction to C++/CLI for C#/Haskell/F#/JS/C++/... programmer

    - by Henrik
    Hello everybody, I'm trying to write integrations with the operating system and with things like active directory and Ocropus. I know a bunch of programming languages, including those listed in the title. I'm trying to learn exactly how C++/CLI works, but can't find succinct, exact and accurate descriptions online from the searching that I have done. So I ask here. Could you tell me the pitfalls and features of C++/CLI? Assume I know all of C# and start from there. I'm not an expert in C++, so some of my questions' answers might be "just like C++", but could say that I am at C#. I would like to know things like: Converting C++ pointers to CLI pointers, Any differences in passing by value/doubly indirect pointers/CLI pointers from C#/C++ and what is 'recommended'. How do gcnew, __gc, __nogc work with Polymorphism Structs Inner classes Interfaces The "fixed" keyword; does that exist? Compiling DLLs loaded into the kernel with C++/CLI possible? Loaded as device drivers? Invoked by the kernel? What does this mean anyway (i.e. to load something into the kernel exactly; how do I know if it is?)? L"my string" versus "my string"? wchar_t? How many types of chars are there? Are we safe in treating chars as uint32s or what should one treat them as to guarantee language indifference in code? Finalizers (~ClassName() {}) are discouraged in C# because there are no garantuees they will run deterministically, but since in C++ I have to use "delete" or use copy-c'tors as to stack allocate memory, what are the recommendations between C#/C++ interactions? What are the pitfalls when using reflection in C++/CLI? How well does C++/CLI work with the IDisposable pattern and with SafeHandle, SafeHandleZeroOrMinusOneIsInvalid? I've read briefly about asynchronous exceptions when doing DMA-operations, what are these? Are there limitations you impose upon yourself when using C++ with CLI integration rather than just doing plain C++? Attributes in C++ similar to Attributes in C#? Can I use the full meta-programming patterns available in C++ through templates now and still have it compile like ordinary C++? Have you tried writing C++/CLI with boost? What are the optimal ways of interfacing the boost library with C++/CLI; can you give me an example of passing a lambda expression to an iterator/foldr function? What is the preferred way of exception handling? Can C++/CLI catch managed exceptions now? How well does dynamic IL generation work with C++/CLI? Does it run on Mono? Any other things I ought to know about?

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  • Succinct introduction to C++/CLI for C#/Haskell/F#/JS/C++/... programmer

    - by Henrik
    Hello everybody, I'm trying to write integrations with the operating system and with things like active directory and Ocropus. I know a bunch of programming languages, including those listed in the title. I'm trying to learn exactly how C++/CLI works, but can't find succinct, exact and accurate descriptions online from the searching that I have done. So I ask here. Could you tell me the pitfalls and features of C++/CLI? Assume I know all of C# and start from there. I'm not an expert in C++, so some of my questions' answers might be "just like C++", but could say that I am at C#. I would like to know things like: Converting C++ pointers to CLI pointers, Any differences in passing by value/doubly indirect pointers/CLI pointers from C#/C++ and what is 'recommended'. How do gcnew, __gc, __nogc work with Polymorphism Structs Inner classes Interfaces The "fixed" keyword; does that exist? Compiling DLLs loaded into the kernel with C++/CLI possible? Loaded as device drivers? Invoked by the kernel? What does this mean anyway (i.e. to load something into the kernel exactly; how do I know if it is?)? L"my string" versus "my string"? wchar_t? How many types of chars are there? Are we safe in treating chars as uint32s or what should one treat them as to guarantee language indifference in code? Finalizers (~ClassName() {}) are discouraged in C# because there are no garantuees they will run deterministically, but since in C++ I have to use "delete" or use copy-c'tors as to stack allocate memory, what are the recommendations between C#/C++ interactions? What are the pitfalls when using reflection in C++/CLI? How well does C++/CLI work with the IDisposable pattern and with SafeHandle, SafeHandleZeroOrMinusOneIsInvalid? I've read briefly about asynchronous exceptions when doing DMA-operations, what are these? Are there limitations you impose upon yourself when using C++ with CLI integration rather than just doing plain C++? Attributes in C++ similar to Attributes in C#? Can I use the full meta-programming patterns available in C++ through templates now and still have it compile like ordinary C++? Have you tried writing C++/CLI with boost? What are the optimal ways of interfacing the boost library with C++/CLI; can you give me an example of passing a lambda expression to an iterator/foldr function? What is the preferred way of exception handling? Can C++/CLI catch managed exceptions now? How well does dynamic IL generation work with C++/CLI? Does it run on Mono? Any other things I ought to know about?

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  • Synchronized IEnumerator<T>

    - by Dan Bryant
    I'm putting together a custom SynchronizedCollection<T> class so that I can have a synchronized Observable collection for my WPF application. The synchronization is provided via a ReaderWriterLockSlim, which, for the most part, has been easy to apply. The case I'm having trouble with is how to provide thread-safe enumeration of the collection. I've created a custom IEnumerator<T> nested class that looks like this: private class SynchronizedEnumerator : IEnumerator<T> { private SynchronizedCollection<T> _collection; private int _currentIndex; internal SynchronizedEnumerator(SynchronizedCollection<T> collection) { _collection = collection; _collection._lock.EnterReadLock(); _currentIndex = -1; } #region IEnumerator<T> Members public T Current { get; private set;} #endregion #region IDisposable Members public void Dispose() { var collection = _collection; if (collection != null) collection._lock.ExitReadLock(); _collection = null; } #endregion #region IEnumerator Members object System.Collections.IEnumerator.Current { get { return Current; } } public bool MoveNext() { var collection = _collection; if (collection == null) throw new ObjectDisposedException("SynchronizedEnumerator"); _currentIndex++; if (_currentIndex >= collection.Count) { Current = default(T); return false; } Current = collection[_currentIndex]; return true; } public void Reset() { if (_collection == null) throw new ObjectDisposedException("SynchronizedEnumerator"); _currentIndex = -1; Current = default(T); } #endregion } My concern, however, is that if the Enumerator is not Disposed, the lock will never be released. In most use cases, this is not a problem, as foreach should properly call Dispose. It could be a problem, however, if a consumer retrieves an explicit Enumerator instance. Is my only option to document the class with a caveat implementer reminding the consumer to call Dispose if using the Enumerator explicitly or is there a way to safely release the lock during finalization? I'm thinking not, since the finalizer doesn't even run on the same thread, but I was curious if there other ways to improve this. EDIT After thinking about this a bit and reading the responses (particular thanks to Hans), I've decided this is definitely a bad idea. The biggest issue actually isn't forgetting to Dispose, but rather a leisurely consumer creating deadlock while enumerating. I now only read-lock long enough to get a copy and return the enumerator for the copy.

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  • Java Nimbus LAF with transparent text fields

    - by Software Monkey
    I have an application that uses disabled JTextFields in several places which are intended to be transparent - allowing the background to show through instead of the text field's normal background. When running the new Nimbus LAF these fields are opaque (despite setting setOpaque(false)), and my UI is broken. It's as if the LAF is ignoring the opaque property. Setting a background color explicitly is both difficult in several places, and less than optimal due to background images actually doesn't work - it still paints it's LAF default background over the top, leaving a border-like appearance (the splash screen below has the background explicitly set to match the image). Any ideas on how I can get Nimbus to not paint the background for a JTextField? Note: I need a JTextField, rather than a JLabel, because I need the thread-safe setText(), and wrapping capability. Note: My fallback position is to continue using the system LAF, but Nimbus does look substantially better. See example images below. Conclusions The surprise at this behavior is due to a misinterpretation of what setOpaque() is meant to do - from the Nimbus bug report: This is a problem the the orginal design of Swing and how it has been confusing for years. The issue is setOpaque(false) has had a side effect in exiting LAFs which is that of hiding the background which is not really what it is ment for. It is ment to say that the component my have transparent parts and swing should paint the parent component behind it. It's unfortunate that the Nimbus components also appear not to honor setBackground(null) which would otherwise be the recommended way to stop the background painting. Setting a fully transparent background seems unintuitive to me. In my opinion, setOpaque()/isOpaque() is a faulty public API choice which should have been only: public boolean isFullyOpaque(); I say this, because isOpaque()==true is a contract with Swing that the component subclass will take responsibility for painting it's entire background - which means the parent can skip painting that region if it wants (which is an important performance enhancement). Something external cannot directly change this contract (legitimately), whose fulfillment may be coded into the component. So the opacity of the component should not have been settable using setOpaque(). Instead something like setBackground(null) should cause many components to "no long have a background" and therefore become not fully opaque. By way of example, in an ideal world most components should have an isOpaque() that looks like this: public boolean isOpaque() { return (background!=null); }

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  • Multi-part question about multi-threading, locks and multi-core processors (multi ^ 3)

    - by MusiGenesis
    I have a program with two methods. The first method takes two arrays as parameters, and performs an operation in which values from one array are conditionally written into the other, like so: void Blend(int[] dest, int[] src, int offset) { for (int i = 0; i < src.Length; i++) { int rdr = dest[i + offset]; dest[i + offset] = src[i] > rdr? src[i] : rdr; } } The second method creates two separate sets of int arrays and iterates through them such that each array of one set is Blended with each array from the other set, like so: void CrossBlend() { int[][] set1 = new int[150][75000]; // we'll pretend this actually compiles int[][] set2 = new int[25][10000]; // we'll pretend this actually compiles for (int i1 = 0; i1 < set1.Length; i1++) { for (int i2 = 0; i2 < set2.Length; i2++) { Blend(set1[i1], set2[i2], 0); // or any offset, doesn't matter } } } First question: Since this apporoach is an obvious candidate for parallelization, is it intrinsically thread-safe? It seems like no, since I can conceive a scenario (unlikely, I think) where one thread's changes are lost because a different threads ~simultaneous operation. If no, would this: void Blend(int[] dest, int[] src, int offset) { lock (dest) { for (int i = 0; i < src.Length; i++) { int rdr = dest[i + offset]; dest[i + offset] = src[i] > rdr? src[i] : rdr; } } } be an effective fix? Second question: If so, what would be the likely performance cost of using locks like this? I assume that with something like this, if a thread attempts to lock a destination array that is currently locked by another thread, the first thread would block until the lock was released instead of continuing to process something. Also, how much time does it actually take to acquire a lock? Nanosecond scale, or worse than that? Would this be a major issue in something like this? Third question: How would I best approach this problem in a multi-threaded way that would take advantage of multi-core processors (and this is based on the potentially wrong assumption that a multi-threaded solution would not speed up this operation on a single core processor)? I'm guessing that I would want to have one thread running per core, but I don't know if that's true.

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  • A mysterious compilation error: cannot convert from 'const boost::shared_ptr<T>' to 'const boost::shared_ptr<T>'

    - by Stephane Rolland
    I wanted to protect the access to a log file that I use for multithreaded logging with boostlog library. I tried this stream class class ThreadSafeStream { public: template <typename TInput> const ThreadSafeStream& operator<< (const TInput &tInput) const { // some thread safe file access return *this; } }; using it this way (text_sink is a boostlog object): //... m_spSink.reset(new text_sink); text_sink::locked_backend_ptr pBackend = m_spSink->locked_backend(); const boost::shared_ptr< ThreadSafeStream >& spFileStream = boost::make_shared<ThreadSafeStream>(); pBackend->add_stream(spFileStream); // this causes the compilation error and I get this mysterious error: cannot convert from 'const boost::shared_ptr<T>' to 'const boost::shared_ptr<T>' the whole compile error: Log.cpp(79): error C2664: 'boost::log2_mt_nt5::sinks::basic_text_ostream_backend<CharT>::add_stream' : cannot convert parameter 1 from 'const boost::shared_ptr<T>' to 'const boost::shared_ptr<T> &' 1> with 1> [ 1> CharT=char 1> ] 1> and 1> [ 1> T=ThreadSafeStream 1> ] 1> and 1> [ 1> T=std::basic_ostream<char,std::char_traits<char>> 1> ] 1> Reason: cannot convert from 'const boost::shared_ptr<T>' to 'const boost::shared_ptr<T>' 1> with 1> [ 1> T=ThreadSafeStream 1> ] 1> and 1> [ 1> T=std::basic_ostream<char,std::char_traits<char>> 1> ] 1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called I suspect that I am not well defining the operator<<()... but I don't find what is wrong.

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  • hibernate column uniqueness question

    - by Seth
    I'm still in the process of learning hibernate/hql and I have a question that's half best practices question/half sanity check. Let's say I have a class A: @Entity public class A { @Id @GeneratedValue(strategy=GenerationType.AUTO) private Long id; @Column(unique=true) private String name = ""; //getters, setters, etc. omitted for brevity } I want to enforce that every instance of A that gets saved has a unique name (hence the @Column annotation), but I also want to be able to handle the case where there's already an A instance saved that has that name. I see two ways of doing this: 1) I can catch the org.hibernate.exception.ConstraintViolationException that could be thrown during the session.saveOrUpdate() call and try to handle it. 2) I can query for existing instances of A that already have that name in the DAO before calling session.saveOrUpdate(). Right now I'm leaning towards approach 2, because in approach 1 I don't know how to programmatically figure out which constraint was violated (there are a couple of other unique members in A). Right now my DAO.save() code looks roughly like this: public void save(A a) throws DataAccessException, NonUniqueNameException { Session session = sessionFactory.getCurrentSession(); try { session.beginTransaction(); Query query = null; //if id isn't null, make sure we don't count this object as a duplicate if(obj.getId() == null) { query = session.createQuery("select count(a) from A a where a.name = :name").setParameter("name", obj.getName()); } else { query = session.createQuery("select count(a) from A a where a.name = :name " + "and a.id != :id").setParameter("name", obj.getName()).setParameter("name", obj.getName()); } Long numNameDuplicates = (Long)query.uniqueResult(); if(numNameDuplicates > 0) throw new NonUniqueNameException(); session.saveOrUpdate(a); session.getTransaction().commit(); } catch(RuntimeException e) { session.getTransaction().rollback(); throw new DataAccessException(e); //my own class } } Am I going about this in the right way? Can hibernate tell me programmatically (i.e. not as an error string) which value is violating the uniqueness constraint? By separating the query from the commit, am I inviting thread-safety errors, or am I safe? How is this usually done? Thanks!

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  • Why does one loop take longer to detect a shared memory update than another loop?

    - by Joseph Garvin
    I've written a 'server' program that writes to shared memory, and a client program that reads from the memory. The server has different 'channels' that it can be writing to, which are just different linked lists that it's appending items too. The client is interested in some of the linked lists, and wants to read every node that's added to those lists as it comes in, with the minimum latency possible. I have 2 approaches for the client: For each linked list, the client keeps a 'bookmark' pointer to keep its place within the linked list. It round robins the linked lists, iterating through all of them over and over (it loops forever), moving each bookmark one node forward each time if it can. Whether it can is determined by the value of a 'next' member of the node. If it's non-null, then jumping to the next node is safe (the server switches it from null to non-null atomically). This approach works OK, but if there are a lot of lists to iterate over, and only a few of them are receiving updates, the latency gets bad. The server gives each list a unique ID. Each time the server appends an item to a list, it also appends the ID number of the list to a master 'update list'. The client only keeps one bookmark, a bookmark into the update list. It endlessly checks if the bookmark's next pointer is non-null ( while(node->next_ == NULL) {} ), if so moves ahead, reads the ID given, and then processes the new node on the linked list that has that ID. This, in theory, should handle large numbers of lists much better, because the client doesn't have to iterate over all of them each time. When I benchmarked the latency of both approaches (using gettimeofday), to my surprise #2 was terrible. The first approach, for a small number of linked lists, would often be under 20us of latency. The second approach would have small spats of low latencies but often be between 4,000-7,000us! Through inserting gettimeofday's here and there, I've determined that all of the added latency in approach #2 is spent in the loop repeatedly checking if the next pointer is non-null. This is puzzling to me; it's as if the change in one process is taking longer to 'publish' to the second process with the second approach. I assume there's some sort of cache interaction going on I don't understand. What's going on?

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  • How to efficiently save changes made in UI/main thread with Core Data?

    - by Jaanus
    So, there have been several posts here about importing and saving data from an external data source into Core Data. Apple documents a reasonable pattern for this: "import and save on background thread, merge saved objects to main thread." All fine and good. I have a related but different problem: the user is modifying data in the UI and main thread, and thus modifies state of some objects in the managed object context (MOC). I would like to save these changes from time to time. What is a good way to do that? Now, you could say that I could do the same: create a background thread with its own MOC and pass the changed objectID-s there. The catch-22 for me with this is that an object's ID changes when it is saved, and I cannot guarantee the order of things happening. I may end up passing a different objectID into the background thread for the same object, based on whether the object has been previously saved or not, and I don't know if Core Data can resolve this and see that different objectID-s are pointing to the same object and not create duplicates for me. (I could test this, but I'm lazywebbing with this question first.) One thought I had: I could always do MOC saves on a background thread, and queue them up with operationqueue, so that there is always only one save in progress. I would not create a new MOC, I would just use the same MOC as in main thread. Now, this is not thread safe and when someone modifies the MOC in main thread while it is being saved in background thread, the results will probably be catastrophic. But, minus the thread safety, you can see what kind of solution I'd wish for. To be clear, the problem I need to fix is that if I just do the save in main thread, it blocks the UI for an unacceptably long period of time, I want to move the save to background thread. So, questions: what about the reasoning of an object ID changing during saving, and Core Data being able to resolve them to the same object? Would this be the right way of addressing this problem? any other good ways of doing this?

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  • "EXC_BAD_ACCESS: Unable to restore previously selected frame" Error, Array size?

    - by Job
    Hi there, I have an algorithm for creating the sieve of Eratosthenes and pulling primes from it. It lets you enter a max value for the sieve and the algorithm gives you the primes below that value and stores these in a c-style array. Problem: Everything works fine with values up to 500.000, however when I enter a large value -while running- it gives me the following error message in xcode: Program received signal: “EXC_BAD_ACCESS”. warning: Unable to restore previously selected frame. Data Formatters temporarily unavailable, will re-try after a 'continue'. (Not safe to call dlopen at this time.) My first idea was that I didn't use large enough variables, but as I am using 'unsigned long long int', this should not be the problem. Also the debugger points me to a point in my code where a point in the array get assigned a value. Therefore I wonder is there a maximum limit to an array? If yes: should I use NSArray instead? If no, then what is causing this error based on this information? EDIT: This is what the code looks like (it's not complete, for it fails at the last line posted). I'm using garbage collection. /*--------------------------SET UP--------------------------*/ unsigned long long int upperLimit = 550000; // unsigned long long int sieve[upperLimit]; unsigned long long int primes[upperLimit]; unsigned long long int indexCEX; unsigned long long int primesCounter = 0; // Fill sieve with 2 to upperLimit for(unsigned long long int indexA = 0; indexA < upperLimit-1; ++indexA) { sieve[indexA] = indexA+2; } unsigned long long int prime = 2; /*-------------------------CHECK & FIND----------------------------*/ while(!((prime*prime) > upperLimit)) { //check off all multiples of prime for(unsigned long long int indexB = prime-2; indexB < upperLimit-1; ++indexB) { // Multiple of prime = 0 if(sieve[indexB] != 0) { if(sieve[indexB] % prime == 0) { sieve[indexB] = 0; } } } /*---------------- Search for next prime ---------------*/ // index of current prime + 1 unsigned long long int indexC = prime - 1; while(sieve[indexC] == 0) { ++indexC; } prime = sieve[indexC]; // Store prime in primes[] primes[primesCounter] = prime; // This is where the code fails if upperLimit > 500000 ++primesCounter; indexCEX = indexC + 1; } As you may or may not see, is that I am -very much- a beginner. Any other suggestions are welcome of course :)

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  • quartz: preventing concurrent instances of a job in jobs.xml

    - by Jason S
    This should be really easy. I'm using Quartz running under Apache Tomcat 6.0.18, and I have a jobs.xml file which sets up my scheduled job that runs every minute. What I would like to do, is if the job is still running when the next trigger time rolls around, I don't want to start a new job, so I can let the old instance complete. Is there a way to specify this in jobs.xml (prevent concurrent instances)? If not, is there a way I can share access to an in-memory singleton within my application's Job implementation (is this through the JobExecutionContext?) so I can handle the concurrency myself? (and detect if a previous instance is running) update: After floundering around in the docs, here's a couple of approaches I am considering, but either don't know how to get them to work, or there are problems. Use StatefulJob. This prevents concurrent access... but I'm not sure what other side-effects would occur if I use it, also I want to avoid the following situation: Suppose trigger times would be every minute, i.e. trigger#0 = at time 0, trigger #1 = 60000msec, #2 = 120000, #3 = 180000, etc. and the trigger#0 at time 0 fires my job which takes 130000msec. With a plain Job, this would execute triggers #1 and #2 while job trigger #0 is still running. With a StatefulJob, this would execute triggers #1 and #2 in order, immediately after #0 finishes at 130000. I don't want that, I want #1 and #2 not to run and the next trigger that runs a job should take place at #3 (180000msec). So I still have to do something else with StatefulJob to get it to work the way I want, so I don't see much of an advantage to using it. Use a TriggerListener to return true from vetoJobExecution(). Although implementing the interface seems straightforward, I have to figure out how to setup one instance of a TriggerListener declaratively. Can't find the docs for the xml file. Use a static shared thread-safe object (e.g. a semaphore or whatever) owned by my class that implements Job. I don't like the idea of using singletons via the static keyword under Tomcat/Quartz, not sure if there are side effects. Also I really don't want them to be true singletons, just something that is associated with a particular job definition. Implement my own Trigger which extends SimpleTrigger and contains shared state that could run its own TriggerListener. Again, I don't know how to setup the XML file to use this trigger rather than the standard <trigger><simple>...</simple></trigger>.

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  • Git repo planning questions

    - by masonk
    At work, development uses perforce to handle code sharing. I won't say "revision control", because we aren't allowed to check in changes until they are ready for regression testing. In order to get my personal change sets under revision control, I've been given the go-ahead to build my own git and initialize the client view of the perforce depot as a git repo. There are some difficulties in doing this, however. The client view lives in a subfolder of ~, (~/p4), and I want to put ~ under revision control as well, with its own separate history. I can't figure out how to keep the history for ~ separate from ~/p4 without using a submodule. The problem with a submodule is that it looks like I have to go make a repository that will become the submodule and then git submodule add <repo> <path>. But there is nowhere to make the submodule's repository except in ~. There seems to be no safe place to create the initial client view of the depot with git p4 clone. (I'm working off of the assumption that initing or cloning a repo into a subdirectory of a git repo is not supported. At least, I can find nothing authoritative on nested git repos.) edit: Is merely ignoring ~/p4 in the repo rooted at ~ enough to allow me to init a nested repo in ~/p4? My __git_ps1 function still thinks I'm in a git repository when I visit an ignored subdirectory of a git repo, so I'm inclined to think not. I need the "remote" repository created by git p4 sync to be a branch in ~/p4. We are required to keep all of our code in ~/p4 so that it doesn't get backed up. Can I pull from a "remote" branch that is really a local branch? This one is just for convenience, but I thought I could learn something by asking it. For 99% of the project, I just want to start the with the p4 head revision as the inital commit object. For the other 1%, I would like to suck down the entire p4 history so that I can browse it in git. IOW, after I'm done initalizing it, the initial commit of remotes/p4/master branch will contain: revision 1 of //depot/prod/Foo/Bar/* revision X of other files in //depot/prod/*, where X is the head revision and the remotes/p4/master branch contains Y commits, where Y is the number of changelists that had a file in //depot/prod/Foo/Bar/*, with each commit in the history corresponding to one of those p4 changelists, and HEAD looking like p4's head.

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  • Verify Authenticode signature as being from our company for automatic updater

    - by James Johnston
    I am implementing an automatic update feature and need some advice on how to do this securely using best practices. I would like to use the downloaded file's Authenticode signature to verify that it is safe to run (i.e. originates from our company and hasn't been tampered with). My question is very similar to question #2008519. The bottom-line question: what's the best, most secure way to check Authenticode signatures for an automatic update feature? What fields in the certificate should be checked? Requirements being: (1) check signature is valid, (2) check it's my signature, (3) old clients can still update when my certificate expires and I get a new one. Here's some background information / ideas from my research: I believe this could be broken into two steps: Verify that the signature is valid. I believe this should be easy using WinVerifyTrust as outlined in http://msdn.microsoft.com/en-us/library/aa382384(VS.85).aspx - I don't expect problems here. Verify that the signature corresponds to our company, and not another company. This seems to be a more difficult question to answer: One possibility is to check some of the strings in the signature. Could be obtained via code at MS KB article #323809, but this article doesn't make recommendations on what fields should be checked for this type of application (or any other, for that matter). Question #1072540 also illustrates how to get some certificate info, but again doesn't recommend what fields to actually check. My concern is that the strings might not be the best check: what if another person is able to obtain a certificate with the same name, for example? Or if there's a valid reason for us to change the strings in the future? The person at question #2008519 has a very similar requirement. His need for a "TrustedByUs" function is identical to mine. However, he goes about doing the check by comparing public keys. While this would work in the short-term, it seems like it won't work for an automatic update feature. This is because code signing certificates are only valid for 2 - 3 years max. Therefore, in the future, when we buy a new certificate in 2 years, the old clients wouldn't be able to update any more due to the change in public key.

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  • Bulk inserts into sqlite db on the iphone...

    - by akaii
    I'm inserting a batch of 100 records, each containing a dictonary containing arbitrarily long HTML strings, and by god, it's slow. On the iphone, the runloop is blocking for several seconds during this transaction. Is my only recourse to use another thread? I'm already using several for acquiring data from HTTP servers, and the sqlite documentation explicitly discourages threading with the database, even though it's supposed to be thread-safe... Is there something I'm doing extremely wrong that if fixed, would drastically reduce the time it takes to complete the whole operation? NSString* statement; statement = @"BEGIN EXCLUSIVE TRANSACTION"; sqlite3_stmt *beginStatement; if (sqlite3_prepare_v2(database, [statement UTF8String], -1, &beginStatement, NULL) != SQLITE_OK) { printf("db error: %s\n", sqlite3_errmsg(database)); return; } if (sqlite3_step(beginStatement) != SQLITE_DONE) { sqlite3_finalize(beginStatement); printf("db error: %s\n", sqlite3_errmsg(database)); return; } NSTimeInterval timestampB = [[NSDate date] timeIntervalSince1970]; statement = @"INSERT OR REPLACE INTO item (hash, tag, owner, timestamp, dictionary) VALUES (?, ?, ?, ?, ?)"; sqlite3_stmt *compiledStatement; if(sqlite3_prepare_v2(database, [statement UTF8String], -1, &compiledStatement, NULL) == SQLITE_OK) { for(int i = 0; i < [items count]; i++){ NSMutableDictionary* item = [items objectAtIndex:i]; NSString* tag = [item objectForKey:@"id"]; NSInteger hash = [[NSString stringWithFormat:@"%@%@", tag, ownerID] hash]; NSInteger timestamp = [[item objectForKey:@"updated"] intValue]; NSData *dictionary = [NSKeyedArchiver archivedDataWithRootObject:item]; sqlite3_bind_int( compiledStatement, 1, hash); sqlite3_bind_text( compiledStatement, 2, [tag UTF8String], -1, SQLITE_TRANSIENT); sqlite3_bind_text( compiledStatement, 3, [ownerID UTF8String], -1, SQLITE_TRANSIENT); sqlite3_bind_int( compiledStatement, 4, timestamp); sqlite3_bind_blob( compiledStatement, 5, [dictionary bytes], [dictionary length], SQLITE_TRANSIENT); while(YES){ NSInteger result = sqlite3_step(compiledStatement); if(result == SQLITE_DONE){ break; } else if(result != SQLITE_BUSY){ printf("db error: %s\n", sqlite3_errmsg(database)); break; } } sqlite3_reset(compiledStatement); } timestampB = [[NSDate date] timeIntervalSince1970] - timestampB; NSLog(@"Insert Time Taken: %f",timestampB); // COMMIT statement = @"COMMIT TRANSACTION"; sqlite3_stmt *commitStatement; if (sqlite3_prepare_v2(database, [statement UTF8String], -1, &commitStatement, NULL) != SQLITE_OK) { printf("db error: %s\n", sqlite3_errmsg(database)); } if (sqlite3_step(commitStatement) != SQLITE_DONE) { printf("db error: %s\n", sqlite3_errmsg(database)); } sqlite3_finalize(beginStatement); sqlite3_finalize(compiledStatement); sqlite3_finalize(commitStatement);

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  • ObjectDisposedException from core .NET code

    - by John
    I'm having this issue with a live app. (Unfortunately this is post-mortem debugging - I only have this stack trace. I've never seen this personally, nor am I able to reproduce). I get this Exception: message=Cannot access a disposed object. Object name: 'Button'. exceptionMessage=Cannot access a disposed object. Object name: 'Button'. exceptionDetails=System.ObjectDisposedException: Cannot access a disposed object. Object name: 'Button'. at System.Windows.Forms.Control.CreateHandle() at System.Windows.Forms.Control.get_Handle() at System.Windows.Forms.Control.PointToScreen(Point p) at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent) at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks) at System.Windows.Forms.Control.WndProc(Message& m) at System.Windows.Forms.ButtonBase.WndProc(Message& m) at System.Windows.Forms.Button.WndProc(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m) at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam) exceptionSource=System.Windows.Forms exceptionTargetSite=Void CreateHandle() It looks like a mouse event is arriving at a form after the form has been disposed. Note there is none of my code in this stack trace. The only weird (?) thing I'm doing, is that I do tend to Dispose() Forms quite aggressively when I use them with ShowModal() (see "Aside" below). But I only do this after ShowModal() has returned (that should be safe right)? I think I read that events might be queued up in the event queue, but I can't believe this would be the problem. I mean surely the framework must be tolerant to old messages? I can well imagine that under stress messages might back-log and surely the window might go away at any time? Any ideas? If you could even suggest ways of reproducing, that might be useful. John Aside: TBH I've never quite understood whether calling Dispose() after Form.ShowDialog() is strictly necessary - the MSDN docs for ShowDialog() are to my mind a bit ambiguous.

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  • How is IObservable<double>.Average supposed to work?

    - by Dan Tao
    Update Looks like Jon Skeet was right (big surprise!) and the issue was with my assumption about the Average extension providing a continuous average (it doesn't). For the behavior I'm after, I wrote a simple ContinuousAverage extension method, the implementation of which I am including here for the benefit of others who may want something similar: public static class ObservableExtensions { private class ContinuousAverager { private double _mean; private long _count; public ContinuousAverager() { _mean = 0.0; _count = 0L; } // undecided whether this method needs to be made thread-safe or not // seems that ought to be the responsibility of the IObservable (?) public double Add(double value) { double delta = value - _mean; _mean += (delta / (double)(++_count)); return _mean; } } public static IObservable<double> ContinousAverage(this IObservable<double> source) { var averager = new ContinuousAverager(); return source.Select(x => averager.Add(x)); } } I'm thinking of going ahead and doing something like the above for the other obvious candidates as well -- so, ContinuousCount, ContinuousSum, ContinuousMin, ContinuousMax ... perhaps ContinuousVariance and ContinuousStandardDeviation as well? Any thoughts on that? Original Question I use Rx Extensions a little bit here and there, and feel I've got the basic ideas down. Now here's something odd: I was under the impression that if I wrote this: var ticks = Observable.FromEvent<QuoteEventArgs>(MarketDataProvider, "MarketTick"); var bids = ticks .Where(e => e.EventArgs.Quote.HasBid) .Select(e => e.EventArgs.Quote.Bid); var bidsSubscription = bids.Subscribe( b => Console.WriteLine("Bid: {0}", b) ); var avgOfBids = bids.Average(); var avgOfBidsSubscription = avgOfBids.Subscribe( b => Console.WriteLine("Avg Bid: {0}", b) ); I would get two IObservable<double> objects (bids and avgOfBids); one would basically be a stream of all the market bids from my MarketDataProvider, the other would be a stream of the average of these bids. So something like this: Bid Avg Bid 1 1 2 1.5 1 1.33 2 1.5 It seems that my avgOfBids object isn't doing anything. What am I missing? I think I've probably misunderstood what Average is actually supposed to do. (This also seems to be the case for all of the aggregate-like extension methods on IObservable<T> -- e.g., Max, Count, etc.)

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