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  • Is it bad to have an "Obsessive Refactoring Disorder"?

    - by Rachel
    I was reading this question and realized that could almost be me. I am fairly OCD about refactoring someone else's code when I see that I can improve it. For example, if the code contains duplicate methods to do the same thing with nothing more than a single parameter changing, I feel I have to remove all the copy/paste methods and replace it with one generic one. Is this bad? Should I try and stop? I try not to refactor unless I can actually make improvements to the code performance or readability, or if the person who did the code isn't following our standard naming conventions (I hate expecting a variable to be local because of the naming standard, only to discover it is a global variable which has been incorrectly named)

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  • Generating a Google Drive Hosted Website with tools you have lying around in your kitchen

    Generating a Google Drive Hosted Website with tools you have lying around in your kitchen Now that you can host web content in Google Drive, Ali will take a look at writing some code to generate a website from files stored in Google Drive. This should be a fun session, and as will all live coding, totally able to fail in about a million ways. From: GoogleDevelopers Views: 0 0 ratings Time: 03:30:00 More in Science & Technology

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  • Google Chrome Extensions: Identity, Signing and Auto Update

    Google Chrome Extensions: Identity, Signing and Auto Update Antony Sargent, a software engineer at Google discusses topics related to ids, packaging and distribution of extensions in the Google Chrome Extension system. To get more information, visit code.google.com/chrome/extensions From: GoogleDevelopers Views: 27337 54 ratings Time: 04:08 More in Science & Technology

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  • fsockopen() error : Network is unreachable port 43 in php [closed]

    - by hamid
    i've writed some Php code that lookup for domain (whois) but it fails !! this is some of my code : function checkdomain($server,$domain){ global $response; $connection = fsockopen($server,43); fputs($connection, "domain " . $domain . "\r\n"); while(!feof($connection)){ $response .= fgets($connection, 4096); } fclose($connection); } checkdomain("whois.crsnic.net","www.example.com"); the code work on my localhost ( apache,php,mysql, OS - Win XP ) but when i uploaded it to my host (Linux) it failed. and i always see the Below Error/message : Warning: fsockopen() [function.fsockopen]: unable to connect to whois.crsnic.net:43 (Network is unreachable) in /home/hamid0011/public_html/whois/whois.php on line 37 what should i do ? is this my host's problem or whois server ( but it work in localhost ) or my code ? TNX

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  • Google Python Class Day 2 Part 2

    Google Python Class Day 2 Part 2 Google Python Class Day 2 Part 2: Utilities: OS and Commands. By Nick Parlante. Support materials and exercises: code.google.com From: GoogleDevelopers Views: 11 1 ratings Time: 20:20 More in Science & Technology

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  • YouTube Direct: Getting Started Guide

    YouTube Direct: Getting Started Guide Jeff Posnick narrates a screencast detailing all aspects of getting started with youtube Direct, from required downloads to configuration to deployment. For even more information about youtube Direct, see code.google.com From: GoogleDevelopers Views: 9685 32 ratings Time: 19:58 More in Science & Technology

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  • .NET 4: &ldquo;Slim&rdquo;-style performance boost!

    - by Vitus
    RTM version of .NET 4 and Visual Studio 2010 is available, and now we can do some test with it. Parallel Extensions is one of the most valuable part of .NET 4.0. It’s a set of good tools for easily consuming multicore hardware power. And it also contains some “upgraded” sync primitives – Slim-version. For example, it include updated variant of widely known ManualResetEvent. For people, who don’t know about it: you can sync concurrency execution of some pieces of code with this sync primitive. Instance of ManualResetEvent can be in 2 states: signaled and non-signaled. Transition between it possible by Set() and Reset() methods call. Some shortly explanation: Thread 1 Thread 2 Time mre.Reset(); mre.WaitOne(); //code execution 0 //wating //code execution 1 //wating //code execution 2 //wating //code execution 3 //wating mre.Set(); 4 //code execution //… 5 Upgraded version of this primitive is ManualResetEventSlim. The idea in decreasing performance cost in case, when only 1 thread use it. Main concept in the “hybrid sync schema”, which can be done as following:   internal sealed class SimpleHybridLock : IDisposable { private Int32 m_waiters = 0; private AutoResetEvent m_waiterLock = new AutoResetEvent(false);   public void Enter() { if (Interlocked.Increment(ref m_waiters) == 1) return; m_waiterLock.WaitOne(); }   public void Leave() { if (Interlocked.Decrement(ref m_waiters) == 0) return; m_waiterLock.Set(); }   public void Dispose() { m_waiterLock.Dispose(); } } It’s a sample from Jeffry Richter’s book “CLR via C#”, 3rd edition. Primitive SimpleHybridLock have two public methods: Enter() and Leave(). You can put your concurrency-critical code between calls of these methods, and it would executed in only one thread at the moment. Code is really simple: first thread, called Enter(), increase counter. Second thread also increase counter, and suspend while m_waiterLock is not signaled. So, if we don’t have concurrent access to our lock, “heavy” methods WaitOne() and Set() will not called. It’s can give some performance bonus. ManualResetEvent use the similar idea. Of course, it have more “smart” technics inside, like a checking of recursive calls, and so on. I want to know a real difference between classic ManualResetEvent realization, and new –Slim. I wrote a simple “benchmark”: class Program { static void Main(string[] args) { ManualResetEventSlim mres = new ManualResetEventSlim(false); ManualResetEventSlim mres2 = new ManualResetEventSlim(false);   ManualResetEvent mre = new ManualResetEvent(false);   long total = 0; int COUNT = 50;   for (int i = 0; i < COUNT; i++) { mres2.Reset(); Stopwatch sw = Stopwatch.StartNew();   ThreadPool.QueueUserWorkItem((obj) => { //Method(mres, true); Method2(mre, true); mres2.Set(); }); //Method(mres, false); Method2(mre, false);   mres2.Wait(); sw.Stop();   Console.WriteLine("Pass {0}: {1} ms", i, sw.ElapsedMilliseconds); total += sw.ElapsedMilliseconds; }   Console.WriteLine(); Console.WriteLine("==============================="); Console.WriteLine("Done in average=" + total / (double)COUNT); Console.ReadLine(); }   private static void Method(ManualResetEventSlim mre, bool value) { for (int i = 0; i < 9000000; i++) { if (value) { mre.Set(); } else { mre.Reset(); } } }   private static void Method2(ManualResetEvent mre, bool value) { for (int i = 0; i < 9000000; i++) { if (value) { mre.Set(); } else { mre.Reset(); } } } } I use 2 concurrent thread (the main thread and one from thread pool) for setting and resetting ManualResetEvents, and try to run test COUNT times, and calculate average execution time. Here is the results (I get it on my dual core notebook with T7250 CPU and Windows 7 x64): ManualResetEvent ManualResetEventSlim Difference is obvious and serious – in 10 times! So, I think preferable way is using ManualResetEventSlim, because not always on calling Set() and Reset() will be called “heavy” methods for working with Windows kernel-mode objects. It’s a small and nice improvement! ;)

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  • .NET Reflector Pro to the rescue

    Almost all applications have to interface with components or modules written by somebody else, for which you don't have the source code. This is fine until things go wrong, but when you need to refactor your code and you keep getting strange exceptions, you'll start to wish you could place breakpoints in someone else's code and step through it. Now, of course, you can, as Geoffrey Braaf discovered.

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  • Goto for the Java Programming Language

    - by darcy
    Work on JDK 8 is well-underway, but we thought this late-breaking JEP for another language change for the platform couldn't wait another day before being published. Title: Goto for the Java Programming Language Author: Joseph D. Darcy Organization: Oracle. Created: 2012/04/01 Type: Feature State: Funded Exposure: Open Component: core/lang Scope: SE JSR: 901 MR Discussion: compiler dash dev at openjdk dot java dot net Start: 2012/Q2 Effort: XS Duration: S Template: 1.0 Reviewed-by: Duke Endorsed-by: Edsger Dijkstra Funded-by: Blue Sun Corporation Summary Provide the benefits of the time-testing goto control structure to Java programs. The Java language has a history of adding new control structures over time, the assert statement in 1.4, the enhanced for-loop in 1.5,and try-with-resources in 7. Having support for goto is long-overdue and simple to implement since the JVM already has goto instructions. Success Metrics The goto statement will allow inefficient and verbose recursive algorithms and explicit loops to be replaced with more compact code. The effort will be a success if at least twenty five percent of the JDK's explicit loops are replaced with goto's. Coordination with IDE vendors is expected to help facilitate this goal. Motivation The goto construct offers numerous benefits to the Java platform, from increased expressiveness, to more compact code, to providing new programming paradigms to appeal to a broader demographic. In JDK 8, there is a renewed focus on using the Java platform on embedded devices with more modest resources than desktop or server environments. In such contexts, static and dynamic memory footprint is a concern. One significant component of footprint is the code attribute of class files and certain classes of important algorithms can be expressed more compactly using goto than using other constructs, saving footprint. For example, to implement state machines recursively, some parties have asked for the JVM to support tail calls, that is, to perform a complex transformation with security implications to turn a method call into a goto. Such complicated machinery should not be assumed for an embedded context. A better solution is just to expose to the programmer the desired functionality, goto. The web has familiarized users with a model of traversing links among different HTML pages in a free-form fashion with some state being maintained on the side, such as login credentials, to effect behavior. This is exactly the programming model of goto and code. While in the past this has been derided as leading to "spaghetti code," spaghetti is a tasty and nutritious meal for programmers, unlike quiche. The invokedynamic instruction added by JSR 292 exposes the JVM's linkage operation to programmers. This is a low-level operation that can be leveraged by sophisticated programmers. Likewise, goto is a also a low-level operation that should not be hidden from programmers who can use more efficient idioms. Some may object that goto was consciously excluded from the original design of Java as one of the removed feature from C and C++. However, the designers of the Java programming languages have revisited these removals before. The enum construct was also left out only to be added in JDK 5 and multiple inheritance was left out, only to be added back by the virtual extension method methods of Project Lambda. As a living language, the needs of the growing Java community today should be used to judge what features are needed in the platform tomorrow; the language should not be forever bound by the decisions of the past. Description From its initial version, the JVM has had two instructions for unconditional transfer of control within a method, goto (0xa7) and goto_w (0xc8). The goto_w instruction is used for larger jumps. All versions of the Java language have supported labeled statements; however, only the break and continue statements were able to specify a particular label as a target with the onerous restriction that the label must be lexically enclosing. The grammar addition for the goto statement is: GotoStatement: goto Identifier ; The new goto statement similar to break except that the target label can be anywhere inside the method and the identifier is mandatory. The compiler simply translates the goto statement into one of the JVM goto instructions targeting the right offset in the method. Therefore, adding the goto statement to the platform is only a small effort since existing compiler and JVM functionality is reused. Other language changes to support goto include obvious updates to definite assignment analysis, reachability analysis, and exception analysis. Possible future extensions include a computed goto as found in gcc, which would replace the identifier in the goto statement with an expression having the type of a label. Testing Since goto will be implemented using largely existing facilities, only light levels of testing are needed. Impact Compatibility: Since goto is already a keyword, there are no source compatibility implications. Performance/scalability: Performance will improve with more compact code. JVMs already need to handle irreducible flow graphs since goto is a VM instruction.

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  • Windows Phone 7 Prototype 002: Animated Page Transitions + Writeable Bitmaps

    Motion is a key part of WP7 application development. Without motion, the WP7 UI is just a bunch of text. Not nearly as exciting. To delight users, you can add some transitions between pages.  The sample app includes some storyboards to animate between two pages. Other people have noted that you can just use the transitioning content control form the SIlverlight toolkit. Peter Torr also had a nice animating frame control in his mix demo code (his blog has some other great code samples for WP7 app dev). I took some of those concepts and the code from the TransitioningContentControl to make a new animating frame control. In this prototype, the frame takes a snapshot of the old content and the new content using writeable bitmaps and animates the snapshots and then replaces those with the actual page. The benefit is smoother animation on pages with lots of controls. Otherwise, if you have a large panorama, it might not animate that cleanly.  Like the other solutions based on the TransitioningContentControl, you can centralize all the animations in one place and not have to handle them on each individual page. Peters code also had a nice snippet for choosing the animation based on the navigation direction so you could just have a forward / backward animation and not have to do anything on each page. You could also probably add some more advanced transitions using pixel shaders or make an default no transition state if you wanted to have some specific animation on a page where individual  controls transitioned out differently like some of the WP7 shell apps. Sample Code 100% guaranteed to work on my emulatorDid you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Google I/O 2010 - Developing web apps for Chrome Web Store

    Google I/O 2010 - Developing web apps for Chrome Web Store Google I/O 2010 - Developing web apps for the Chrome Web Store Chrome 101 Erik Kay Google Chrome is a powerful platform for developing web apps. With Chrome web apps, we're making it easier for users to discover and use these apps. Learn how to build and sell apps for the Chrome Web Store. For all I/O 2010 sessions, please go to code.google.com From: GoogleDevelopers Views: 8 0 ratings Time: 01:00:29 More in Science & Technology

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  • Google Chrome Extensions Developer Snapshots - Web of Trust

    Google Chrome Extensions Developer Snapshots - Web of Trust Deborah Salmi, CMO of WOT (www.mywot.com) discusses her company's experience with the Google Chrome extensions platform. To learn more on creating Google Chrome Extensions please visit code.google.com/chrome/extensions or chek out the gallery at chrome.google.com/extensions. From: GoogleDevelopers Views: 5 0 ratings Time: 05:39 More in Science & Technology

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  • Style bits vs. Separate bool's

    - by peterchen
    My main platform (WinAPI) still heavily uses bits for control styles etc. (example). When introducing custom controls, I'm permanently wondering whether to follow that style or rather use individual bool's. Let's pit them against each other: enum EMyCtrlStyles { mcsUseFileIcon = 1, mcsTruncateFileName = 2, mcsUseShellContextMenu = 4, }; void SetStyle(DWORD mcsStyle); void ModifyStyle(DWORD mcsRemove, DWORD mcsAdd); DWORD GetStyle() const; ... ctrl.SetStyle(mcsUseFileIcon | mcsUseShellContextMenu); vs. CMyCtrl & SetUseFileIcon(bool enable = true); bool GetUseFileIcon() const; CMyCtrl & SetTruncteFileName(bool enable = true); bool GetTruncteFileName() const; CMyCtrl & SetUseShellContextMenu(bool enable = true); bool GetUseShellContextMenu() const; ctrl.SetUseFileIcon().SetUseShellContextMenu(); As I see it, Pro Style Bits Consistent with platform less library code (without gaining complexity), less places to modify for adding a new style less caller code (without losing notable readability) easier to use in some scenarios (e.g. remembering / transferring settings) Binary API remains stable if new style bits are introduced Now, the first and the last are minor in most cases. Pro Individual booleans Intellisense and refactoring tools reduce the "less typing" effort Single Purpose Entities more literate code (as in "flows more like a sentence") No change of paradim for non-bool properties These sound more modern, but also "soft" advantages. I must admit the "platform consistency" is much more enticing than I could justify, the less code without losing much quality is a nice bonus. 1. What do you prefer? Subjectively, for writing the library, or for writing client code? 2. Any (semi-) objective statements, studies, etc.?

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  • Intercept method calls in Groovy for automatic type conversion

    - by kerry
    One of the cooler things you can do with groovy is automatic type conversion.  If you want to convert an object to another type, many times all you have to do is invoke the ‘as’ keyword: def letters = 'abcdefghijklmnopqrstuvwxyz' as List But, what if you are wanting to do something a little fancier, like converting a String to a Date? def christmas = '12-25-2010' as Date ERROR org.codehaus.groovy.runtime.typehandling.GroovyCastException: Cannot cast object '12-25-2010' with class java.lang.String' to class 'java.util.Date' No bueno! I want to be able to do custom type conversions so that my application can do a simple String to Date conversion. Enter the metaMethod. You can intercept method calls in Groovy using the following method: def intercept(name, params, closure) { def original = from.metaClass.getMetaMethod(name, params) from.metaClass[name] = { Class clazz -> closure() original.doMethodInvoke(delegate, clazz) } } Using this method, and a little syntactic sugar, we create the following ‘Convert’ class: // Convert.from( String ).to( Date ).using { } class Convert { private from private to private Convert(clazz) { from = clazz } static def from(clazz) { new Convert(clazz) } def to(clazz) { to = clazz return this } def using(closure) { def originalAsType = from.metaClass.getMetaMethod('asType', [] as Class[]) from.metaClass.asType = { Class clazz -> if( clazz == to ) { closure.setProperty('value', delegate) closure(delegate) } else { originalAsType.doMethodInvoke(delegate, clazz) } } } } Now, we can make the following statement to add the automatic date conversion: Convert.from( String ).to( Date ).using { new java.text.SimpleDateFormat('MM-dd-yyyy').parse(value) } def christmas = '12-25-2010' as Date Groovy baby!

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  • Beginner's guide to writing comments?

    - by Cameron
    Is there a definitive guide to writing code comments, aimed at budding developers? Ideally, it would cover when comments should (and should not) be used, and what comments should contain. This answer: Do not comment WHAT you are doing, but WHY you are doing it. The WHAT is taken care of by clean, readable and simple code with proper choice of variable names to support it. Comments show a higher level structure to the code that can't be (or is hard to) show by the code itself. comes close, but it's a little concise for inexperienced programmers (an expansion on that with several examples and corner cases would be excellent, I think).

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  • Keeping Aspect Screen Ratio While Stays in Center

    - by David Dimalanta
    I sqw and I tried this suggestion on PISTACHIO BRAINSTORMIN* on how to make a good and adaptive screen ration. For every different screen size, let's say I put the perfect circle as a Texture in LibGDX and played it on screen. Here's the blueberry image example and it's perfectly rounded: When I played it on the Google Nexus 7, the circle turn into a slightly oblonng shape, resembling as it was being flatten a bit. Please observe this snapshot below and you can see the blueberry is almost but slightly not perfectly rounded: Now, when I tried the suggested code for aspect ratio, the perfect circle retained but another problem is occured. The problem is that I expecting for a view on center but instead it's been moved to the right offset leaving with a half black screen. This would be look like this: Here is my code using the suggested screen aspect ratio code: Class' Field // Ingredients Needed for Screen Aspect Ratio private static final int VIRTUAL_WIDTH = 720; private static final int VIRTUAL_HEIGHT = 1280; private static final float ASPECT_RATIO = ((float) VIRTUAL_WIDTH)/((float) VIRTUAL_HEIGHT); private Camera Mother_Camera; private Rectangle Viewport; render() // Camera updating... Mother_Camera.update(); Mother_Camera.apply(Gdx.gl10); // Reseting viewport... Gdx.gl.glViewport((int) Viewport.x, (int) Viewport.y, (int) Viewport.width, (int) Viewport.height); // Clear previous frame. Gdx.gl.glClearColor(0, 0, 0, 1); Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT); show() Mother_Camera = new OrthographicCamera(VIRTUAL_WIDTH, VIRTUAL_HEIGHT); Was this code useful for screen aspect ratio-proportion fixing or it is statically dependent on actual device's width and height? *see http://blog.acamara.es/2012/02/05/keep-screen-aspect-ratio-with-different-resolutions-using-libgdx/#comment-317

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  • Sort Data in Windows Phone using Collection View Source

    - by psheriff
    When you write a Windows Phone application you will most likely consume data from a web service somewhere. If that service returns data to you in a sort order that you do not want, you have an easy alternative to sort the data without writing any C# or VB code. You use the built-in CollectionViewSource object in XAML to perform the sorting for you. This assumes that you can get the data into a collection that implements the IEnumerable or IList interfaces.For this example, I will be using a simple Product class with two properties, and a list of Product objects using the Generic List class. Try this out by creating a Product class as shown in the following code:public class Product {  public Product(int id, string name)   {    ProductId = id;    ProductName = name;  }  public int ProductId { get; set; }  public string ProductName { get; set; }}Create a collection class that initializes a property called DataCollection with some sample data as shown in the code below:public class Products : List<Product>{  public Products()  {    InitCollection();  }  public List<Product> DataCollection { get; set; }  List<Product> InitCollection()  {    DataCollection = new List<Product>();    DataCollection.Add(new Product(3,        "PDSA .NET Productivity Framework"));    DataCollection.Add(new Product(1,        "Haystack Code Generator for .NET"));    DataCollection.Add(new Product(2,        "Fundamentals of .NET eBook"));    return DataCollection;  }}Notice that the data added to the collection is not in any particular order. Create a Windows Phone page and add two XML namespaces to the Page.xmlns:scm="clr-namespace:System.ComponentModel;assembly=System.Windows"xmlns:local="clr-namespace:WPSortData"The 'local' namespace is an alias to the name of the project that you created (in this case WPSortData). The 'scm' namespace references the System.Windows.dll and is needed for the SortDescription class that you will use for sorting the data. Create a phone:PhoneApplicationPage.Resources section in your Windows Phone page that looks like the following:<phone:PhoneApplicationPage.Resources>  <local:Products x:Key="products" />  <CollectionViewSource x:Key="prodCollection"      Source="{Binding Source={StaticResource products},                       Path=DataCollection}">    <CollectionViewSource.SortDescriptions>      <scm:SortDescription PropertyName="ProductName"                           Direction="Ascending" />    </CollectionViewSource.SortDescriptions>  </CollectionViewSource></phone:PhoneApplicationPage.Resources>The first line of code in the resources section creates an instance of your Products class. The constructor of the Products class calls the InitCollection method which creates three Product objects and adds them to the DataCollection property of the Products class. Once the Products object is instantiated you now add a CollectionViewSource object in XAML using the Products object as the source of the data to this collection. A CollectionViewSource has a SortDescriptions collection that allows you to specify a set of SortDescription objects. Each object can set a PropertyName and a Direction property. As you see in the above code you set the PropertyName equal to the ProductName property of the Product object and tell it to sort in an Ascending direction.All you have to do now is to create a ListBox control and set its ItemsSource property to the CollectionViewSource object. The ListBox displays the data in sorted order by ProductName and you did not have to write any LINQ queries or write other code to sort the data!<ListBox    ItemsSource="{Binding Source={StaticResource prodCollection}}"   DisplayMemberPath="ProductName" />SummaryIn this blog post you learned that you can sort any data without having to change the source code of where the data comes from. Simply feed the data into a CollectionViewSource in XAML and set some sort descriptions in XAML and the rest is done for you! This comes in very handy when you are consuming data from a source where the data is given to you and you do not have control over the sorting.NOTE: You can download this article and many samples like the one shown in this blog entry at my website. http://www.pdsa.com/downloads. Select “Tips and Tricks”, then “Sort Data in Windows Phone using Collection View Source” from the drop down list.Good Luck with your Coding,Paul Sheriff** SPECIAL OFFER FOR MY BLOG READERS **We frequently offer a FREE gift for readers of my blog. Visit http://www.pdsa.com/Event/Blog for your FREE gift!

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  • SharePoint Web Part Constructor Fires Twice When Adding it to the Page (and has a different security

    - by Damon
    We had some exciting times debugging an interesting issue with SharePoint 2007 Web Parts.  We had some code in staging that had been running just fine for weeks and had not been touched or changed in about the same amount of time.  However, when we tried to move the web part into a different staging environment, the part started throwing a security exception when we tried to add it to a page.  After a bit of debugging, we determined that the web part was throwing the exception while trying to access the SPGroups property on the SharePoint site.  This was pretty strange because we were logged in as an admin and the code was working perfectly fine before.  During the debugging process, however, we found out that the web part constructor was being fired twice.  On one request, the security context did not seem to have everything it needed in order to run.  On the other request, the security context was populated with the user context with the user making the request (like it normally is).  Moving the security code outside of the constructor seems to have fixed the issue. Why the discrepancy between the two staging environments?  Turns out we deployed the part originally, then deployed an update with the security code.  Since the part was never "added" to the page after the code updates were made (we just deployed a new assembly to make the updates), we never saw the problem.  It seems as though the constructor fires twice when you are adding the web part to the page, and when you run the web part from the web part gallery.  My only thought on why this would occur is that SharePoint is instantiating an instance to get some information from it - which is odd because you would think that would happen with reflection without requiring a new object.  Anyway, the work around is to just not put anything security related inside the constructor, or to do a good job accounting for the possibility of the security context not being present if you are adding the item to the page. Technorati Tags: SharePoint,.NET,Microsoft,ASP.NET

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  • Google Python Class Day 1 Part 1

    Google Python Class Day 1 Part 1 Google Python Class Day 1 Part 1: Introduction and Strings. By Nick Parlante. Support materials and exercises: code.google.com From: GoogleDevelopers Views: 137 1 ratings Time: 51:37 More in Science & Technology

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  • Looking for some OO design advice

    - by Andrew Stephens
    I'm developing an app that will be used to open and close valves in an industrial environment, and was thinking of something simple like this:- public static void ValveController { public static void OpenValve(string valveName) { // Implementation to open the valve } public static void CloseValve(string valveName) { // Implementation to close the valve } } (The implementation would write a few bytes of data to the serial port to control the valve - an "address" derived from the valve name, and either a "1" or "0" to open or close the valve). Another dev asked whether we should instead create a separate class for each physical valve, of which there are dozens. I agree it would be nicer to write code like PlasmaValve.Open() rather than ValveController.OpenValve("plasma"), but is this overkill? Also, I was wondering how best to tackle the design with a couple of hypothetical future requirements in mind:- We are asked to support a new type of valve requiring different values to open and close it (not 0 and 1). We are asked to support a valve that can be set to any position from 0-100, rather than simply "open" or "closed". Normally I would use inheritance for this kind of thing, but I've recently started to get my head around "composition over inheritance" and wonder if there is a slicker solution to be had using composition?

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  • Taming Hopping Windows

    - by Roman Schindlauer
    At first glance, hopping windows seem fairly innocuous and obvious. They organize events into windows with a simple periodic definition: the windows have some duration d (e.g. a window covers 5 second time intervals), an interval or period p (e.g. a new window starts every 2 seconds) and an alignment a (e.g. one of those windows starts at 12:00 PM on March 15, 2012 UTC). var wins = xs     .HoppingWindow(TimeSpan.FromSeconds(5),                    TimeSpan.FromSeconds(2),                    new DateTime(2012, 3, 15, 12, 0, 0, DateTimeKind.Utc)); Logically, there is a window with start time a + np and end time a + np + d for every integer n. That’s a lot of windows. So why doesn’t the following query (always) blow up? var query = wins.Select(win => win.Count()); A few users have asked why StreamInsight doesn’t produce output for empty windows. Primarily it’s because there is an infinite number of empty windows! (Actually, StreamInsight uses DateTimeOffset.MaxValue to approximate “the end of time” and DateTimeOffset.MinValue to approximate “the beginning of time”, so the number of windows is lower in practice.) That was the good news. Now the bad news. Events also have duration. Consider the following simple input: var xs = this.Application                 .DefineEnumerable(() => new[]                     { EdgeEvent.CreateStart(DateTimeOffset.UtcNow, 0) })                 .ToStreamable(AdvanceTimeSettings.IncreasingStartTime); Because the event has no explicit end edge, it lasts until the end of time. So there are lots of non-empty windows if we apply a hopping window to that single event! For this reason, we need to be careful with hopping window queries in StreamInsight. Or we can switch to a custom implementation of hopping windows that doesn’t suffer from this shortcoming. The alternate window implementation produces output only when the input changes. We start by breaking up the timeline into non-overlapping intervals assigned to each window. In figure 1, six hopping windows (“Windows”) are assigned to six intervals (“Assignments”) in the timeline. Next we take input events (“Events”) and alter their lifetimes (“Altered Events”) so that they cover the intervals of the windows they intersect. In figure 1, you can see that the first event e1 intersects windows w1 and w2 so it is adjusted to cover assignments a1 and a2. Finally, we can use snapshot windows (“Snapshots”) to produce output for the hopping windows. Notice however that instead of having six windows generating output, we have only four. The first and second snapshots correspond to the first and second hopping windows. The remaining snapshots however cover two hopping windows each! While in this example we saved only two events, the savings can be more significant when the ratio of event duration to window duration is higher. Figure 1: Timeline The implementation of this strategy is straightforward. We need to set the start times of events to the start time of the interval assigned to the earliest window including the start time. Similarly, we need to modify the end times of events to the end time of the interval assigned to the latest window including the end time. The following snap-to-boundary function that rounds a timestamp value t down to the nearest value t' <= t such that t' is a + np for some integer n will be useful. For convenience, we will represent both DateTime and TimeSpan values using long ticks: static long SnapToBoundary(long t, long a, long p) {     return t - ((t - a) % p) - (t > a ? 0L : p); } How do we find the earliest window including the start time for an event? It’s the window following the last window that does not include the start time assuming that there are no gaps in the windows (i.e. duration < interval), and limitation of this solution. To find the end time of that antecedent window, we need to know the alignment of window ends: long e = a + (d % p); Using the window end alignment, we are finally ready to describe the start time selector: static long AdjustStartTime(long t, long e, long p) {     return SnapToBoundary(t, e, p) + p; } To find the latest window including the end time for an event, we look for the last window start time (non-inclusive): public static long AdjustEndTime(long t, long a, long d, long p) {     return SnapToBoundary(t - 1, a, p) + p + d; } Bringing it together, we can define the translation from events to ‘altered events’ as in Figure 1: public static IQStreamable<T> SnapToWindowIntervals<T>(IQStreamable<T> source, TimeSpan duration, TimeSpan interval, DateTime alignment) {     if (source == null) throw new ArgumentNullException("source");     // reason about DateTime and TimeSpan in ticks     long d = Math.Min(DateTime.MaxValue.Ticks, duration.Ticks);     long p = Math.Min(DateTime.MaxValue.Ticks, Math.Abs(interval.Ticks));     // set alignment to earliest possible window     var a = alignment.ToUniversalTime().Ticks % p;     // verify constraints of this solution     if (d <= 0L) { throw new ArgumentOutOfRangeException("duration"); }     if (p == 0L || p > d) { throw new ArgumentOutOfRangeException("interval"); }     // find the alignment of window ends     long e = a + (d % p);     return source.AlterEventLifetime(         evt => ToDateTime(AdjustStartTime(evt.StartTime.ToUniversalTime().Ticks, e, p)),         evt => ToDateTime(AdjustEndTime(evt.EndTime.ToUniversalTime().Ticks, a, d, p)) -             ToDateTime(AdjustStartTime(evt.StartTime.ToUniversalTime().Ticks, e, p))); } public static DateTime ToDateTime(long ticks) {     // just snap to min or max value rather than under/overflowing     return ticks < DateTime.MinValue.Ticks         ? new DateTime(DateTime.MinValue.Ticks, DateTimeKind.Utc)         : ticks > DateTime.MaxValue.Ticks         ? new DateTime(DateTime.MaxValue.Ticks, DateTimeKind.Utc)         : new DateTime(ticks, DateTimeKind.Utc); } Finally, we can describe our custom hopping window operator: public static IQWindowedStreamable<T> HoppingWindow2<T>(     IQStreamable<T> source,     TimeSpan duration,     TimeSpan interval,     DateTime alignment) {     if (source == null) { throw new ArgumentNullException("source"); }     return SnapToWindowIntervals(source, duration, interval, alignment).SnapshotWindow(); } By switching from HoppingWindow to HoppingWindow2 in the following example, the query returns quickly rather than gobbling resources and ultimately failing! public void Main() {     var start = new DateTimeOffset(new DateTime(2012, 6, 28), TimeSpan.Zero);     var duration = TimeSpan.FromSeconds(5);     var interval = TimeSpan.FromSeconds(2);     var alignment = new DateTime(2012, 3, 15, 12, 0, 0, DateTimeKind.Utc);     var events = this.Application.DefineEnumerable(() => new[]     {         EdgeEvent.CreateStart(start.AddSeconds(0), "e0"),         EdgeEvent.CreateStart(start.AddSeconds(1), "e1"),         EdgeEvent.CreateEnd(start.AddSeconds(1), start.AddSeconds(2), "e1"),         EdgeEvent.CreateStart(start.AddSeconds(3), "e2"),         EdgeEvent.CreateStart(start.AddSeconds(9), "e3"),         EdgeEvent.CreateEnd(start.AddSeconds(3), start.AddSeconds(10), "e2"),         EdgeEvent.CreateEnd(start.AddSeconds(9), start.AddSeconds(10), "e3"),     }).ToStreamable(AdvanceTimeSettings.IncreasingStartTime);     var adjustedEvents = SnapToWindowIntervals(events, duration, interval, alignment);     var query = from win in HoppingWindow2(events, duration, interval, alignment)                 select win.Count();     DisplayResults(adjustedEvents, "Adjusted Events");     DisplayResults(query, "Query"); } As you can see, instead of producing a massive number of windows for the open start edge e0, a single window is emitted from 12:00:15 AM until the end of time: Adjusted Events StartTime EndTime Payload 6/28/2012 12:00:01 AM 12/31/9999 11:59:59 PM e0 6/28/2012 12:00:03 AM 6/28/2012 12:00:07 AM e1 6/28/2012 12:00:05 AM 6/28/2012 12:00:15 AM e2 6/28/2012 12:00:11 AM 6/28/2012 12:00:15 AM e3 Query StartTime EndTime Payload 6/28/2012 12:00:01 AM 6/28/2012 12:00:03 AM 1 6/28/2012 12:00:03 AM 6/28/2012 12:00:05 AM 2 6/28/2012 12:00:05 AM 6/28/2012 12:00:07 AM 3 6/28/2012 12:00:07 AM 6/28/2012 12:00:11 AM 2 6/28/2012 12:00:11 AM 6/28/2012 12:00:15 AM 3 6/28/2012 12:00:15 AM 12/31/9999 11:59:59 PM 1 Regards, The StreamInsight Team

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