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• CodePlex Daily Summary for Thursday, March 29, 2012

  CodePlex Daily Summary for Thursday, March 29, 2012Popular ReleasesWouter's SharePoint Demo Land: Custom Views and Forms: Samples showing how to provision custom lists. Custom view rendering with code, XSLT, XSLT + code. Custom forms with database lookups.YouTube API Class & Server Control for ASP.NET 4.0: Binary dll Files with Demo: . You can find binary dll files under :- Demo\bin\ folder Demo url :- http://demo.svinn.com/YouTube/Default.aspx 1 GB Hosting + Free Domain => http://ghosting.in/ .callisto: callisto 2.0.23: Patched Script static class and peak user count bug fix.Circuit Diagram: Circuit Diagram 2.0 Alpha 3: New in this release: Added components: Microcontroller Demultiplexer Flip & rotate components Open XML files from older versions of Circuit Diagram Text formatting for components New CDDX syntax Other fixesUmbraco CMS: Umbraco 5.1 CMS (Beta): Beta build for testing - please report issues at issues.umbraco.org (Latest uploaded: 5.1.0.123) What's new in 5.1? The full list of changes is on our http://progress.umbraco.org task tracking page. It shows items complete for 5.1, and 5.1 includes items for 5.0.1 and 5.0.2 listed there too. Here's two headline acts: Members5.1 adds support for backoffice editing of Members. We support the pairing up of our content type system in Hive with regular ASP.NET Membership providers (we ship a def...51Degrees.mobi - Mobile Device Detection and Redirection: 2.1.2.11: One Click Install from NuGet Changes to Version 2.1.2.11Code Changes 1. The project is now licenced under the Mozilla Public Licence 2. 2. User interface control and associated data access layer classes have been added to aid developers integrating 51Degrees.mobi into wider projects such as content management systems or web hosting management solutions. Use the following in a web form or user control to access these new UI components. <%@ Register Assembly="FiftyOne.Foundation" Namespace="...JSON Toolkit: JSON Toolkit 3.1: slight performance improvement (5% - 10%) new JsonException classPicturethrill: Version 2.3.28.0: Straightforward image selection. New clean UI look. Super stable. Simplified user experience.Indent Guides for Visual Studio: Indent Guides v12 (beta 2): Note This beta is likely to be less stable than the previous one. If you have severe troubles using this version, please report them with as much detail as possible (especially other extensions/addins that you may have) and downgrade to the last stable release. Version History Changed since v12 (beta 1): new options dialog with Quick Set selections for behavior restructured settings storage (should be more reliable) asynchronous background document analysis glow effect now appears in p...SQL Monitor - managing sql server performance: SQL Monitor 4.2 alpha 16: 1. finally fixed problem with logic fault checking for temporary table name... I really mean finally ...ScintillaNET: ScintillaNET 2.5: A slew of bug-fixes with a few new features sprinkled in. This release also upgrades the SciLexer and SciLexer64 DLLs to version 3.0.4. The official stuff: Issue # Title 32402 32402 27137 27137 31548 31548 30179 30179 24932 24932 29701 29701 31238 31238 26875 26875 30052 30052 Mugen MVVM Toolkit: Mugen MVVM Toolkit ver 1.1: Added Design mode support.Multiwfn: Multiwfn 2.3.2: Multiwfn 2.3.2Harness: Harness 2.0.2: change to .NET Framework Client Profile bug fix the download dialog auto answer. bug fix setFocus command. add "SendKeys" command. remove "closeAll" command. minor bugs fixed.BugNET Issue Tracker: BugNET 0.9.161: Below is a list of fixes in this release. Bug BGN-2092 - Link in Email "visit your profile" not functional BGN-2083 - Manager of bugnet can not edit project when it is not public BGN-2080 - clicking on a link in the project summary causes error (0.9.152.0) BGN-2070 - Missing Functionality On Feed.aspx BGN-2069 - Calendar View does not work BGN-2068 - Time tracking totals not ok BGN-2067 - Issues List Page Size Bug: Index was out of range. Must be non-negative and less than the si...YAF.NET (aka Yet Another Forum.NET): v1.9.6.1 RTW: v1.9.6.1 FINAL is .NET v4.0 ONLY v1.9.6.1 has: Performance Improvements .NET v4.0 improvements Improved FaceBook Integration KNOWN ISSUES WITH THIS RELEASE: ON INSTALL PLEASE DON'T CHECK "Upgrade BBCode Extensions...". More complete change list and discussion here: http://forum.yetanotherforum.net/yaf_postst14201_v1-9-6-1-RTW-Dated--3-26-2012.aspxmenu4web: menu4web 0.0.3: menu4web 0.0.3ArcGIS Editor for OpenStreetMap: ArcGIS Editor for OSM 2.0 Final: This release installs both the ArcGIS Editor for OSM Server Component and/or ArcGIS Editor for OSM Desktop components. The Desktop tools allow you to download data from the OpenStreetMap servers and store it locally in a geodatabase. You can then use the familiar editing environment of ArcGIS Desktop to create, modify, or delete data. Once you are done editing, you can post back the edit changes to OSM to make them available to all OSM users. The Server Component allows you to quickly create...Craig's Utility Library: Craig's Utility Library 3.1: This update adds about 60 new extension methods, a couple of new classes, and a number of fixes including: Additions Added DateSpan class Added GenericDelimited class Random additions Added static thread friendly version of Random.Next called ThreadSafeNext. AOP Manager additions Added Destroy function to AOPManager (clears out all data so system can be recreated. Really only useful for testing...) ORM additions Added PagedCommand and PageCount functions to ObjectBaseClass (same as M...DotSpatial: DotSpatial 1.1: This is a Minor Release. See the changes in the issue tracker. Minimal -- includes DotSpatial core and essential extensions Extended -- includes debugging symbols and additional extensions Just want to run the software? End user (non-programmer) version available branded as MapWindow Want to add your own feature? Develop a plugin, using the template and contribute to the extension feed (you can also write extensions that you distribute in other ways). Components are available as NuGet pa...New ProjectsAeroFichierAchats: Program that reworks excel files into PDFArepa: A lightweight non-invasive tool that helps you to implement Behavior Driven Development (BDD) on .NET projects. Arepa produces guidelines of using BDD on your current tests, and customisable and portable test reports integrating XML Documentation Comments. It's developed in C# using Scrum and BDD.Azure User Management Console - AUMC: Azure User Management Console - AUMC is a User Graphic Interface (GUI) that manages the users and logins of an Azure SQL database. The tool is simply converting your action into T-SQL commands and execute them on the Azure SQL Database. BaseProject: BaseProjectCraftBukkit Updater: I don't activly monitor the status of CraftBukkit's updates, but I want to stay on top of the updated versions. This will track the last version in cache then check for updates. Upon update there should be an option to download automaticly to location XYZ or to send an email/sms.Dan Dot Com: Dan's SandboxEjemplos Windows 8 Javascript: Este proyecto pretende recoger todos los ejemplos de aplicaciones metro para Windows 8 en JavaScript que vaya desarrollando para fines didácticos. Todas las colaboraciones son bienvenidas.EntityFramework Generic Patterns: EntityFramework Generic PatternsEpFamvir: EpFamvir is a Visual C++ software framework that supports data-intensive distributed applications under a GPL3.0 license. It enables applications to work with thousands of nodes and petabytes of data. Famvir was inspired by Apache Hadoop, Google's MapReduce, and Google FS.etdc/etp: ???????????????? ???????? ??????? etest.ru. IndieCiv: IndieCiv - An independent look at how a new game could be made using fan-made graphics from Civ3. You can visit the discussion at www.civfanatics.com http://forums.civfanatics.com/showthread.php?t=421582Libro SQL Server 2012: Databases and examples for my Italian book on "SQL Server 2012"Linq2Rest: Parses OData system query parameters to create a LINQ query that can be used to filter a model set. Also exposes a LINQ provider for web services supporting the OData query parameters. Use extension method Filter (in Linq2Rest namespace) on any IEnumerable source.LittleUmph: It's a little library to help you to alleviate some of the mundane stuff during your development. It has some nifty stuff like a neat database wrapper, conversion utilities, string functions and vast of other mini helpers to improve the efficiency and consistency of your code.LonghornRPG: LonghornRPGMemberManager: Keep track of membersMSU Student Teaching DataBase: A C# application to manage student placements for MSU.MvcContrib4: This is the MvcContrib project to support MVC 4MYFIRSTDEMOPROJECT: Introduction to CSharpOrchard Page Title Override: This Orchard CMS module allows a user to manage the Page Title. You can now have the Site Name show up last in the Page Title or hide the Site Name completely from the Page Title. The module also contains a Content Part allowing a Page Title to be separate from content title.phoenixtree: .net linux sql php python html javascript c exampleProject Explorer for Notepad++: This project mainly aims at providing a functional rich project explorer experience on notepad++. Features include Folder based file browsing, searching, filtering and more.Projeto Exemplo FPU: Projeto Exemplo FPUPureCalendar: simple web calendarrails study: rails studySafe IM: a safe IM software use AES,SHA,RSA.Contain a server and a clientScoreboard: Scoreboard is a simple sports and/or activities scoreboard which can be used for a variety of purposes It was developed for use with a 1024x768 projector and features home and away scores, countdown clock, even a buzzer. It's developed in VB.net.SharePoint System dates and editor fields updater: The SPChangeDate is a utility used to modify some of the system fields in a SharePoint 2010 document library using a datagridview (Excel Like). It allows the modification of the following SharePoint fields: 1. Created 2. Modified 3. Modified By 4. Created By Shi Ji Xiang CRM 2012: Shi Ji XiangSIGECAR: SIGECARStable Dependencies Principle Checker for nDepend: Small console app for parsing nDepend output files and find assemblies that breaks the Stable Dependencies PrincipleStudentsPointManager: StudentsPointManagertclh123test: 4testThai Sign Language Translator: Thai Sign Language Translator with Kinect Sensor.The House FM / My Praise FM Desktop App: An App to play Christian radio on the desktop of windows Vista and Windows 7 computersTradeSea: Uni ProjectVisual Dependency Tracer: This tool will help you understand how an excel formula is derived/calculated. It provides a visual representation (tree) of the formula, including the precendents and dependents.VK Video Player: Video player for russian social network vk.comXrmSvcToolkit: XrmSvcToolkit is a small JavaScript library that helps you access Microsoft Dynamics CRM 2011 web service interfaces (SOAP and REST).

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• "Authorize" attribute and 403 error page

  - by zerkms

  [Authorize] property is nice and handy MS invention, and I hope it can solve the issues I have now To be more specific: When current client isn't authenticated - [Authorize] redirects from secured action to logon page and after logon was successfull - brings user back, this is good. But when current cilent already authenticated but not authorized to run specific action - all I need is to just display my general 403 page. Is it possible without moving authorization logic within controller's body? UPD: The behavior I need in should be semantically equals to this sketch: public ActionResult DoWork() { if (!NotAuthorized()) { return RedirectToAction("403"); } return View(); } so - there should no any redirect and url should be stay the same, but contents of the page should be replaced with 403-page

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• How add a ItemsPanel dynamically to listbox.

  - by Subhen

  Hi, I have a list Box which contains few Images in the itemsTemplate , like below: <ListBox.ItemTemplate> <DataTemplate> <StackPanel x:Name="stackPanelItems" Orientation="Horizontal"> <Image Source="{Binding strAlbumcoverImage}" Height="40" Width="40"/> </StackPanel> </DataTemplate> </ListBox.ItemTemplate> Now onClick of a button I want to change the view and for that I want to add the wrap panel to the ListBox ItemsPanelas following: <ListBox.ItemsPanel> <ItemsPanelTemplate> <controlsToolkit:WrapPanel></controlsToolkit:WrapPanel> </ItemsPanelTemplate> </ListBox.ItemsPanel> Do I need to define the ItemsPanel Style in App.XAML and then assign it. Not quite sure about it. Thanks, Subhen

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• Android: How to handle runtime exception on playing audio files?

  - by Maxood

  I have a button that plays an audio file on its click listener. If the button is clicked again and again while the audio file is being played then the app crashes. What's the solution? Here is some code for reference: private OnClickListener btnMercyListener = new OnClickListener() { public void onClick(View v) { // Toast.makeText(getBaseContext(), // "Mercy audio file is being played", // Toast.LENGTH_LONG).show(); if (status==true) { mp.stop(); mp.release(); status = false; } else { mp = MediaPlayer.create(iMEvil.this,R.raw.mercy); //mp.start(); try{ mp.start(); status= true; //mp.release(); }catch(NullPointerException e) { Log.v("MP error",e.toString()); } } mp.setOnCompletionListener(new OnCompletionListener(){ // @Override public void onCompletion(MediaPlayer arg0) { mp.release(); status = false; } } ); } };

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• Can I provide nil for the -dequeueReusableCellWithIdentifier: method?

  - by mystify

  dequeueReusableCellWithIdentifier: Returns a reusable table-view cell object located by its identifier. (UITableViewCell *)dequeueReusableCellWithIdentifier:(NSString *)identifier Parameters identifier A string identifying the cell object to be reused. By default, a reusable cell's identifier is its class name, but you can change it to any arbitrary value. Ok so if by default it's the class name, why should I put much brain force into thinking about an identifier? Could I provide just nil? Would it then use the class name? Or what did they try to say here? Must I make an NSString with the class name by myself and provide it as identifier?

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• Asp.Net Program Architecture

  - by Pino

  I've just taken on a new Asp.Net MVC application and after opening it up I find the following, [Project].Web [Project].Models [Project].BLL [Project].DAL Now, something thats become clear is that there is the data has to do a hell of a lot before it makes it to the View (DatabaseDALRepoBLLConvertToModelControllerView). The DAL is Subsonic, the repositorys in the DAL return the subsonic entities to the BLL which process them does crazy things and converts them into a Model (From the .Models) sometimes with classes that look like this public DataModel GetDataModel(EntityObject Src) { var ReturnData = new DataModel(): ReturnData.ID = Src.ID; ReturnDate.Name = Src.Name; //etc etc } Now, the question is, "Is this complete overkill"? Ok the project is of a decent size and can only get bigger but is it worth carrying on with all this? I dont want to use AutoMapper as it just seems like it makes the complication worse. Can anyone shed any light on this?

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• Big smart ViewModels, dumb Views, and any model, the best MVVM approach?

  - by Edward Tanguay

  The following code is a refactoring of my previous MVVM approach (Fat Models, skinny ViewModels and dumb Views, the best MVVM approach?) in which I moved the logic and INotifyPropertyChanged implementation from the model back up into the ViewModel. This makes more sense, since as was pointed out, you often you have to use models that you either can't change or don't want to change and so your MVVM approach should be able to work with any model class as it happens to exist. This example still allows you to view the live data from your model in design mode in Visual Studio and Expression Blend which I think is significant since you could have a mock data store that the designer connects to which has e.g. the smallest and largest strings that the UI can possibly encounter so that he can adjust the design based on those extremes. Questions: I'm a bit surprised that I even have to "put a timer" in my ViewModel since it seems like that is a function of INotifyPropertyChanged, it seems redundant, but it was the only way I could get the XAML UI to constantly (once per second) reflect the state of my model. So it would be interesting to hear anyone who may have taken this approach if you encountered any disadvantages down the road, e.g. with threading or performance. The following code will work if you just copy the XAML and code behind into a new WPF project. XAML: <Window x:Class="TestMvvm73892.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:TestMvvm73892" Title="Window1" Height="300" Width="300"> <Window.Resources> <ObjectDataProvider x:Key="DataSourceCustomer" ObjectType="{x:Type local:CustomerViewModel}" MethodName="GetCustomerViewModel"/> </Window.Resources> <DockPanel DataContext="{StaticResource DataSourceCustomer}"> <StackPanel DockPanel.Dock="Top" Orientation="Horizontal"> <TextBlock Text="{Binding Path=FirstName}"/> <TextBlock Text=" "/> <TextBlock Text="{Binding Path=LastName}"/> </StackPanel> <StackPanel DockPanel.Dock="Top" Orientation="Horizontal"> <TextBlock Text="{Binding Path=TimeOfMostRecentActivity}"/> </StackPanel> </DockPanel> </Window> Code Behind: using System; using System.Windows; using System.ComponentModel; using System.Threading; namespace TestMvvm73892 { public partial class Window1 : Window { public Window1() { InitializeComponent(); } } //view model public class CustomerViewModel : INotifyPropertyChanged { private string _firstName; private string _lastName; private DateTime _timeOfMostRecentActivity; private Timer _timer; public string FirstName { get { return _firstName; } set { _firstName = value; this.RaisePropertyChanged("FirstName"); } } public string LastName { get { return _lastName; } set { _lastName = value; this.RaisePropertyChanged("LastName"); } } public DateTime TimeOfMostRecentActivity { get { return _timeOfMostRecentActivity; } set { _timeOfMostRecentActivity = value; this.RaisePropertyChanged("TimeOfMostRecentActivity"); } } public CustomerViewModel() { _timer = new Timer(CheckForChangesInModel, null, 0, 1000); } private void CheckForChangesInModel(object state) { Customer currentCustomer = CustomerViewModel.GetCurrentCustomer(); MapFieldsFromModeltoViewModel(currentCustomer, this); } public static CustomerViewModel GetCustomerViewModel() { CustomerViewModel customerViewModel = new CustomerViewModel(); Customer currentCustomer = CustomerViewModel.GetCurrentCustomer(); MapFieldsFromModeltoViewModel(currentCustomer, customerViewModel); return customerViewModel; } public static void MapFieldsFromModeltoViewModel(Customer model, CustomerViewModel viewModel) { viewModel.FirstName = model.FirstName; viewModel.LastName = model.LastName; viewModel.TimeOfMostRecentActivity = model.TimeOfMostRecentActivity; } public static Customer GetCurrentCustomer() { return Customer.GetCurrentCustomer(); } //INotifyPropertyChanged implementation public event PropertyChangedEventHandler PropertyChanged; private void RaisePropertyChanged(string property) { if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(property)); } } } //model public class Customer { public string FirstName { get; set; } public string LastName { get; set; } public DateTime TimeOfMostRecentActivity { get; set; } public static Customer GetCurrentCustomer() { return new Customer { FirstName = "Jim", LastName = "Smith", TimeOfMostRecentActivity = DateTime.Now }; } } }

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• How can I tell when a UIWebView has finished drawing to a context?

  - by phopkins

  In my code I'm trying to show a UIWebView as a page is loading, and then, when it's done, capture an image from the web view to cache and display later (so I don't have to reload and render the web page). I have something along the lines of: CGContextRef context = CGBitmapContextCreate(…); [[webView layer] renderInContext:context]; CGImageRef imageRef = CGBitmapContextCreateImage(context); UIImage *image = [UIImage imageWithCGImage:imageRef]; The problem I'm running into is that, due to UIWebView's tiling, sometimes only half of the page is rendered to the context by the time I capture the image. Is there a way to detect or block on UIWebView's background rendering thread so that I can get the image only after all of the rendering has finished?

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• Using jQuery to load Telerik MVC scripts.

  - by ProfK

  I'm busy building my first MVC app that uses the Telerik MVC components. Their docs specify that the ScriptRegistrar helper be called right at the bottom of a view, e.g. "at the end of the master page.". I assume this renders a script block that must only run when the page has loaded. I normally prefer to achieve this using jQuery, and keep all my script related stuff at the top of my master page, preferably in the <head> tag. Is there anything I can do to achieve this with the Telerik components and do away with the lone and forgotten helper call at the bottom of my master page?

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• Preparing a Universal App for iPhone SDK 3.2

  - by user133611

  Hi all, I am working on a universal app, I used UISplitViewController in doing iPad application. I followed the Universal app guidelines i.e, i keep base SDK as 3.2, iPhone Target OS ad iPhone OS 3.1.3, Taget device as iPhone/iPad. And i used "Adding Runtime Checks for Newer Symbols" for UISplitViewController and UIPopOverController. Class splitVCClass = NSClassFromString(@"UISplitViewController"); if (splitVC) { UISplitViewController* mySplitViewController = [[splitVCClass alloc] init]; // Configure the split view controller. } I used this in .m files I declared UIPopOverController in .h files also "dyld: Symbol not found: _OBJC_CLASS_$_UIPopoverController Referenced from: /var/mobile/Applications/9E0CE75F-D2A9-4132-AE56-1780928BCF21/UniversalTasks.app/UniversalTasks Expected in: /System/Library/Frameworks/UIKit.framework/UIKit in /var/mobile/Applications/9E0CE75F-D2A9-4132-AE56-1780928BCF21/UniversalTasks.app/UniversalTasks" What i have to do can any one help me out

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• Linking Simple product to their page listed under Grouped product in Magento

  - by Yogesh

  I want to add url for each simple product listed under Grouped product in Magento i have changed it with below code in app\design\frontend\blank\default\template\catalog\product\view\type\grouped.phtml but still not work for me it's link but with main group product (Example: Main Grouped product and three simple products Item1 Item2 Item3 but all simple product show same url of ain Grouped product) <td><a href="<?php $_item->getUrlPath() ?>"><?php echo $this->htmlEscape($_item->getName()) ?></a> </td> and this also <td><a href="<?php $_item->getProductUrl() ?>"><?php echo $this->htmlEscape($_item->getName()) ?></a> </td> i am doing any mistek pls. help how and where to change it

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• Alpha transparent PNGs not displaying correctly in Mobile Safari

  - by worksology

  I'm using some semi-transparent PNGs as background-images on various websites. These are usually something like a 1x1 image with a 30-percent opaque white layer. I've noticed that Mobile Safari does not display them correctly, giving them a darker/grayish tint. I've created a couple test pages to illustrate. View them both in your normal browser, and then on Mobile Safari, and you should see what I mean. This shows 11 red images of varying opacities on white: http://thecompleteworks.org/alpha-tests/index-red.html This shows 11 white images of varying opacities on blue: http://thecompleteworks.org/alpha-tests/index.html Is this a MobileSafari bug (I couldn't imagine so), or do I need to do something different, either to my pages or PNGs? (Here's how I create the PNGs: In Photoshop, create a 1x1 transparent canvas. Draw a white rectangle in Layer 1. Set opacity to, say 30 percent, Save for Web as 24-bit PNG with transparency.)

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• WinSCP equivalent for Linux/Ubuntu

  - by Shashank

  I'm shifting most of my projects to a Linux machine, and one of the things that I miss is WinSCP. I've found other answers saying that nautilus, FileZilla etc. can be used for SFTP, but something that I loved about WinSCP was that it has two panes (FileZilla's got that) and I could start synchronization from any directory. Unison or Rsync could work, but I'd have to create a folder pair every time I want to sync two folders. Is there an SFTP client for Linux that has a two-paned view and allows ad-hoc synchronization? Thanks!

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• I want to port my delicious bookmarks to my website

  - by puneet

  I started building a app that will automatically download my delicious bookmarks, and save to a database, so they I can view them on my own website in my favoured format. I am forced to use oAuth, as I have a yahoo id to login to delicious. The problem is I am stuck at the point where oAuth requires a user to manually go and authenticate. Is there a code/ guidelines available anywhere I can follow? All I want is a way to automatically save my bookmarks to my database. Any help is appreciated. I can work on java, .net and php. Thanks.

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• Break nested loop in Django views.py with a function

  - by knuckfubuck

  I have a nested loop that I would like to break out of. After searching this site it seems the best practice is to put the nested loop into a function and use return to break out of it. Is it acceptable to have functions inside the views.py file that are not a view? What is the best practice for the location of this function? Here's the example code from inside my views.py @login_required def save_bookmark(request): if request.method == 'POST': form = BookmarkSaveForm(request.POST) if form.is_valid(): bookmark_list = Bookmark.objects.all() for bookmark in bookmark_list: for link in bookmark.link_set.all(): if link.url == form.cleaned_data['url']: # Do something. break else: # Do something else. else: form = BookmarkSaveForm() return render_to_response('save_bookmark_form.html', {'form': form})

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• Inside the Concurrent Collections: ConcurrentDictionary

  - by Simon Cooper

  Using locks to implement a thread-safe collection is rather like using a sledgehammer - unsubtle, easy to understand, and tends to make any other tool redundant. Unlike the previous two collections I looked at, ConcurrentStack and ConcurrentQueue, ConcurrentDictionary uses locks quite heavily. However, it is careful to wield locks only where necessary to ensure that concurrency is maximised. This will, by necessity, be a higher-level look than my other posts in this series, as there is quite a lot of code and logic in ConcurrentDictionary. Therefore, I do recommend that you have ConcurrentDictionary open in a decompiler to have a look at all the details that I skip over. The problem with locks There's several things to bear in mind when using locks, as encapsulated by the lock keyword in C# and the System.Threading.Monitor class in .NET (if you're unsure as to what lock does in C#, I briefly covered it in my first post in the series): Locks block threads The most obvious problem is that threads waiting on a lock can't do any work at all. No preparatory work, no 'optimistic' work like in ConcurrentQueue and ConcurrentStack, nothing. It sits there, waiting to be unblocked. This is bad if you're trying to maximise concurrency. Locks are slow Whereas most of the methods on the Interlocked class can be compiled down to a single CPU instruction, ensuring atomicity at the hardware level, taking out a lock requires some heavy lifting by the CLR and the operating system. There's quite a bit of work required to take out a lock, block other threads, and wake them up again. If locks are used heavily, this impacts performance. Deadlocks When using locks there's always the possibility of a deadlock - two threads, each holding a lock, each trying to aquire the other's lock. Fortunately, this can be avoided with careful programming and structured lock-taking, as we'll see. So, it's important to minimise where locks are used to maximise the concurrency and performance of the collection. Implementation As you might expect, ConcurrentDictionary is similar in basic implementation to the non-concurrent Dictionary, which I studied in a previous post. I'll be using some concepts introduced there, so I recommend you have a quick read of it. So, if you were implementing a thread-safe dictionary, what would you do? The naive implementation is to simply have a single lock around all methods accessing the dictionary. This would work, but doesn't allow much concurrency. Fortunately, the bucketing used by Dictionary allows a simple but effective improvement to this - one lock per bucket. This allows different threads modifying different buckets to do so in parallel. Any thread making changes to the contents of a bucket takes the lock for that bucket, ensuring those changes are thread-safe. The method that maps each bucket to a lock is the GetBucketAndLockNo method: private void GetBucketAndLockNo( int hashcode, out int bucketNo, out int lockNo, int bucketCount) { // the bucket number is the hashcode (without the initial sign bit) // modulo the number of buckets bucketNo = (hashcode & 0x7fffffff) % bucketCount; // and the lock number is the bucket number modulo the number of locks lockNo = bucketNo % m_locks.Length; } However, this does require some changes to how the buckets are implemented. The 'implicit' linked list within a single backing array used by the non-concurrent Dictionary adds a dependency between separate buckets, as every bucket uses the same backing array. Instead, ConcurrentDictionary uses a strict linked list on each bucket: This ensures that each bucket is entirely separate from all other buckets; adding or removing an item from a bucket is independent to any changes to other buckets. Modifying the dictionary All the operations on the dictionary follow the same basic pattern: void AlterBucket(TKey key, ...) { int bucketNo, lockNo; 1: GetBucketAndLockNo( key.GetHashCode(), out bucketNo, out lockNo, m_buckets.Length); 2: lock (m_locks[lockNo]) { 3: Node headNode = m_buckets[bucketNo]; 4: Mutate the node linked list as appropriate } } For example, when adding another entry to the dictionary, you would iterate through the linked list to check whether the key exists already, and add the new entry as the head node. When removing items, you would find the entry to remove (if it exists), and remove the node from the linked list. Adding, updating, and removing items all follow this pattern. Performance issues There is a problem we have to address at this point. If the number of buckets in the dictionary is fixed in the constructor, then the performance will degrade from O(1) to O(n) when a large number of items are added to the dictionary. As more and more items get added to the linked lists in each bucket, the lookup operations will spend most of their time traversing a linear linked list. To fix this, the buckets array has to be resized once the number of items in each bucket has gone over a certain limit. (In ConcurrentDictionary this limit is when the size of the largest bucket is greater than the number of buckets for each lock. This check is done at the end of the TryAddInternal method.) Resizing the bucket array and re-hashing everything affects every bucket in the collection. Therefore, this operation needs to take out every lock in the collection. Taking out mutiple locks at once inevitably summons the spectre of the deadlock; two threads each hold a lock, and each trying to acquire the other lock. How can we eliminate this? Simple - ensure that threads never try to 'swap' locks in this fashion. When taking out multiple locks, always take them out in the same order, and always take out all the locks you need before starting to release them. In ConcurrentDictionary, this is controlled by the AcquireLocks, AcquireAllLocks and ReleaseLocks methods. Locks are always taken out and released in the order they are in the m_locks array, and locks are all released right at the end of the method in a finally block. At this point, it's worth pointing out that the locks array is never re-assigned, even when the buckets array is increased in size. The number of locks is fixed in the constructor by the concurrencyLevel parameter. This simplifies programming the locks; you don't have to check if the locks array has changed or been re-assigned before taking out a lock object. And you can be sure that when a thread takes out a lock, another thread isn't going to re-assign the lock array. This would create a new series of lock objects, thus allowing another thread to ignore the existing locks (and any threads controlling them), breaking thread-safety. Consequences of growing the array Just because we're using locks doesn't mean that race conditions aren't a problem. We can see this by looking at the GrowTable method. The operation of this method can be boiled down to: private void GrowTable(Node[] buckets) { try { 1: Acquire first lock in the locks array // this causes any other thread trying to take out // all the locks to block because the first lock in the array // is always the one taken out first // check if another thread has already resized the buckets array // while we were waiting to acquire the first lock 2: if (buckets != m_buckets) return; 3: Calculate the new size of the backing array 4: Node[] array = new array[size]; 5: Acquire all the remaining locks 6: Re-hash the contents of the existing buckets into array 7: m_buckets = array; } finally { 8: Release all locks } } As you can see, there's already a check for a race condition at step 2, for the case when the GrowTable method is called twice in quick succession on two separate threads. One will successfully resize the buckets array (blocking the second in the meantime), when the second thread is unblocked it'll see that the array has already been resized & exit without doing anything. There is another case we need to consider; looking back at the AlterBucket method above, consider the following situation: Thread 1 calls AlterBucket; step 1 is executed to get the bucket and lock numbers. Thread 2 calls GrowTable and executes steps 1-5; thread 1 is blocked when it tries to take out the lock in step 2. Thread 2 re-hashes everything, re-assigns the buckets array, and releases all the locks (steps 6-8). Thread 1 is unblocked and continues executing, but the calculated bucket and lock numbers are no longer valid. Between calculating the correct bucket and lock number and taking out the lock, another thread has changed where everything is. Not exactly thread-safe. Well, a similar problem was solved in ConcurrentStack and ConcurrentQueue by storing a local copy of the state, doing the necessary calculations, then checking if that state is still valid. We can use a similar idea here: void AlterBucket(TKey key, ...) { while (true) { Node[] buckets = m_buckets; int bucketNo, lockNo; GetBucketAndLockNo( key.GetHashCode(), out bucketNo, out lockNo, buckets.Length); lock (m_locks[lockNo]) { // if the state has changed, go back to the start if (buckets != m_buckets) continue; Node headNode = m_buckets[bucketNo]; Mutate the node linked list as appropriate } break; } } TryGetValue and GetEnumerator And so, finally, we get onto TryGetValue and GetEnumerator. I've left these to the end because, well, they don't actually use any locks. How can this be? Whenever you change a bucket, you need to take out the corresponding lock, yes? Indeed you do. However, it is important to note that TryGetValue and GetEnumerator don't actually change anything. Just as immutable objects are, by definition, thread-safe, read-only operations don't need to take out a lock because they don't change anything. All lockless methods can happily iterate through the buckets and linked lists without worrying about locking anything. However, this does put restrictions on how the other methods operate. Because there could be another thread in the middle of reading the dictionary at any time (even if a lock is taken out), the dictionary has to be in a valid state at all times. Every change to state has to be made visible to other threads in a single atomic operation (all relevant variables are marked volatile to help with this). This restriction ensures that whatever the reading threads are doing, they never read the dictionary in an invalid state (eg items that should be in the collection temporarily removed from the linked list, or reading a node that has had it's key & value removed before the node itself has been removed from the linked list). Fortunately, all the operations needed to change the dictionary can be done in that way. Bucket resizes are made visible when the new array is assigned back to the m_buckets variable. Any additions or modifications to a node are done by creating a new node, then splicing it into the existing list using a single variable assignment. Node removals are simply done by re-assigning the node's m_next pointer. Because the dictionary can be changed by another thread during execution of the lockless methods, the GetEnumerator method is liable to return dirty reads - changes made to the dictionary after GetEnumerator was called, but before the enumeration got to that point in the dictionary. It's worth listing at this point which methods are lockless, and which take out all the locks in the dictionary to ensure they get a consistent view of the dictionary: Lockless: TryGetValue GetEnumerator The indexer getter ContainsKey Takes out every lock (lockfull?): Count IsEmpty Keys Values CopyTo ToArray Concurrent principles That covers the overall implementation of ConcurrentDictionary. I haven't even begun to scratch the surface of this sophisticated collection. That I leave to you. However, we've looked at enough to be able to extract some useful principles for concurrent programming: Partitioning When using locks, the work is partitioned into independant chunks, each with its own lock. Each partition can then be modified concurrently to other partitions. Ordered lock-taking When a method does need to control the entire collection, locks are taken and released in a fixed order to prevent deadlocks. Lockless reads Read operations that don't care about dirty reads don't take out any lock; the rest of the collection is implemented so that any reading thread always has a consistent view of the collection. That leads us to the final collection in this little series - ConcurrentBag. Lacking a non-concurrent analogy, it is quite different to any other collection in the class libraries. Prepare your thinking hats!

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• Downloading Video on iPhone using SDK

  - by Vivek Navadia

  Hello All I would like to develop such iphone application that provides functionality to download viedo. i am doing some as below 1) Loading HTML content on web view 2) The loaded html content contains the video link (i.e http://test.com/test.mp4") 3) When i click on that it will play the video in native player. 4) but i would like to prevent this thing and start downloading video from that URL for example, if i click on link it should not open native video player, it should start downloading from that url and store somewhere on iphone (i.e document directory) is there any solution for same? Thanks Vivek

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• SQL datasource for gridview

  - by Karsten

  Hi I want to use a gridview with sorting and paging to display data from an SQL server, the query uses 3 joins and the full text search containstable. The from part of the query uses all 3 tables in the join. What is the best way to do this? I can think of a stored procedure, SQL directly in the SQLDataSource and creating a view in the database. I want good performance and would like to leverage the automatic sorting and paging features of the gridview as much as possible.

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• Trouble with onscreen keyboard orientation in iPhone OpenGL ES application.

  - by Plumenator

  I need to take keyboard input in my OpenGL ES application, so I just created an empty UITextView and added it as a subview to the main window along with the view that presents my content. I use the UITextview to control the keyboard and it works fine in a single orientation. I then changed my code to support all orientations by rotating the OpenGL content myself based on UIDeviceOrientation notifications. To rotate the keyboard, I overrode the shouldAutoRotateInterfaceOrientation method in the UITextView's controller. But I still see that the keyboard does not rotate according to the orientation. Any clues?

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• Problem when loading image from google chart api URL

  - by user304839

  I want to show concentric charts of google api in iphone, but the imageData varible returns null value and image does not loaded from url to image view this is code: NSData *imageData = [[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:@"http://chart.apis.google.com/chart?cht=pc&chd=t:120,45|120,60,50,70,60&chs=300x200&chl=||helo|wrd|india|pak|ban&chco=FFFFFF|FFFFFF,e72a28|a9d331|ffce08|8a2585|184a7d"]]; NSLog(@"%@",imageData); UIImage *myimage = [[UIImage alloc] initWithData:imageData]; self.myImageView.image=myimage; please any one help me to overcome on this problem

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• Trouble setting a default controller in MVC 2 RC Area

  - by mannish

  This should be simple, but alas... I've set up an Admin area within my MVC 2 project (single project areas). I've created a couple controllers and their respective view folders. In the AreaRegistration.RegisterArea method, I've specified that I want the default controller to be "Dashboard": public override void RegisterArea(AreaRegistrationContext context) { context.MapRoute( "Admin_default", "Admin/{controller}/{action}/{id}", new { controller = "Dashboard", action = "Index", id = "" }, new string[] { "Admin" } ); } If I navigate to url/Admin/Dashboard, the index comes up just fine. What I want, though, is to allow the user to go to url/Admin/ and see the same thing. When I do this, however, I get "The resource cannot be found". I'm just getting my feet wet with MVC 2's Area implementation, and I don't think I'm doing anything overly complicated... Anyone had the same problem? Do I need to specify a separate route, perhaps at the root, non-area level?

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• UIButton Origin and Device Orientation

  - by Ward

  Hey there, I might be crazy, but for some reason this problem is stumping me. I have a view controller that is set to auto rotate to orientation. Inside I've got two subviews. One is a uibutton. All I want is for my button's origin to stay locked to the bottom-left in portrait and bottom-right in landscape (so it basically stays in the same place). It should also stay in place for portrait upside down and landscape right. Any ideas? Thanks, Howie

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• missing duration in iis 7.5 Failed Request Tracing on server core

  - by Phil McCracken

  We have Failed Request Tracing working on IIS7.5 (Windows 2008 Server Core) and our rule has ASP.NET checked off and verbose logging set. However, on many googled screenshots of what a typical failed request trace looks like, we see the actual duration of each subpart in milliseconds shown to the right of the word verbose on the "request details" tab. Viewing our XML in IE shows no such thing to the right of the word verbose. Furthermore, The "Performance View" tab is blank; so no help viewing the durations there either. Is there something we need to enable? What gives?

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• Is there a suggested solution structure for ASP.NET MVC Production Apps

  - by Eoin Campbell

  In general, I don't like to keep code (BaseClasses or DataAccess Code) in the App_Code directory of an ASP.NET Site. I'll usually pull this stuff out into a MySite.BusinessLogic & MySite.DataAccess DLL's respectively. I'm wondering should I be doing the same for ASP.NET MVC. Would it be better to Organise the solution something along the lines of MySite.Common - DLL - (Basic Functionality built on .NET System Dlls) MySite.DAL - DLL - (DataAccessLayer & DBML Files) MySite.Models - DLL - (MVC Models e.g. Repository Classes) MySite.Controllers - DLL (MVC Controllers which use Models) MySite - ASP.NET MVC Site. Or am I missing something... presumably, I'll lose some of the nice (Add View, Go To Controller, context menu items that have been added)

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• What parser generator do you recommend

  - by stefan.ciobaca

  I'm currently shopping for a FOSS parser generator for a project of mine. It has to support either C or C++. I've looked at bison/flex and at boost::spirit. I went from writing my own to spirit to bison to spirit to bison to spirit, each time hit by some feature I found unpleasant. The thing I hate most about bison/flex is that they actually generate C/C++ source for you. There are a number of disadvantages to this, e.g. debugging. I like spirit from this point of view, but I find it very very heavy on syntax. I am curious about what you are using, what you would recommend, and general thoughts about the state of the art in parser generators. I am also curious to hear about approaches being used in other languages for parsing problems.

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