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  • What do you do before you start programming?

    - by SterAllures
    Heya, I'm not sure this question belongs here, it's not so much I problem I'm having with programming but rather a problem of what to do before I start programming. I want a visual representation of what variables I need and what classes have what methods.I know there is UML but I'm not sure if that is the best way, so what do you guys use before you start programming, which method? I don't want to start a flamewar about what is better just what are several approaches?

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  • Blazing Keywords - The Google Blazing Keywords Review

    Many people who are currently attempting different methods of online marketing in order to promote and build their business have heard that keyword research is extremely vital to the success of your online marketing. Unfortunately most online marketing companies do not properly teach their members how to effectively do their keyword research in order to get good results and because of that many people are left to look for services that promise to do this for them.

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  • Test interface implementation

    - by Michael
    I have a interface in our code base that I would like to be able to mock out for unit testing. I am writing a test implementation to allow the individual tests to be able to override the specific methods they are concerned with rather than implementing every method. I've run into a quandary over how the test implementation should behave if the test fails to override a method used by the method under test. Should I return a "non-value" (0, null) in the test implementation or throw a UnsupportedOperationException to explicitly fail the test?

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  • Referential Integrity: Best Practices for IBM DB2

    Of the various constraints possible on relational tables, referential constraints are perhaps the most common ... and most misused. Learn about the advantages and disadvantages of different methods to implement and enforce RI, and issues that must be addressed when implementing DBMS-enforced Referential Integrity.

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  • Changing CSS with jQuery syntax in Silverlight using jLight

    - by Timmy Kokke
    Lately I’ve ran into situations where I had to change elements or had to request a value in the DOM from Silverlight. jLight, which was introduced in an earlier article, can help with that. jQuery offers great ways to change CSS during runtime. Silverlight can access the DOM, but it isn’t as easy as jQuery. All examples shown in this article can be looked at in this online demo. The code can be downloaded here.   Part 1: The easy stuff Selecting and changing properties is pretty straight forward. Setting the text color in all <B> </B> elements can be done using the following code:   jQuery.Select("b").Css("color", "red");   The Css() method is an extension method on jQueryObject which is return by the jQuery.Select() method. The Css() method takes to parameters. The first is the Css style property. All properties used in Css can be entered in this string. The second parameter is the value you want to give the property. In this case the property is “color” and it is changed to “red”. To specify which element you want to select you can add a :selector parameter to the Select() method as shown in the next example.   jQuery.Select("b:first").Css("font-family", "sans-serif");   The “:first” pseudo-class selector selects only the first element. This example changes the “font-family” property of the first <B></B> element to “sans-serif”. To make use of intellisense in Visual Studio I’ve added a extension methods to help with the pseudo-classes. In the example below the “font-weight” of every “Even” <LI></LI> is set to “bold”.   jQuery.Select("li".Even()).Css("font-weight", "bold");   Because the Css() extension method returns a jQueryObject it is possible to chain calls to Css(). The following example show setting the “color”, “background-color” and the “font-size” of all headers in one go.   jQuery.Select(":header").Css("color", "#12FF70") .Css("background-color", "yellow") .Css("font-size", "25px");   Part 2: More complex stuff In only a few cases you need to change only one style property. More often you want to change an entire set op style properties all in one go.  You could chain a lot of Css() methods together. A better way is to add a class to a stylesheet and define all properties in there. With the AddClass() method you can set a style class to a set of elements. This example shows how to add the “demostyle” class to all <B></B> in the document.   jQuery.Select("b").AddClass("demostyle");   Removing the class works in the same way:   jQuery.Select("b").RemoveClass("demostyle");   jLight is build for interacting with to the DOM from Silverlight using jQuery. A jQueryObjectCss object can be used to define different sets of style properties in Silverlight. The over 60 most common Css style properties are defined in the jQueryObjectCss class. A string indexer can be used to access all style properties ( CssObject1[“background-color”] equals CssObject1.BackgroundColor). In the code below, two jQueryObjectCss objects are defined and instantiated.   private jQueryObjectCss CssObject1; private jQueryObjectCss CssObject2;   public Demo2() { CssObject1 = new jQueryObjectCss { BackgroundColor = "Lime", Color="Black", FontSize = "12pt", FontFamily = "sans-serif", FontWeight = "bold", MarginLeft = 150, LineHeight = "28px", Border = "Solid 1px #880000" }; CssObject2 = new jQueryObjectCss { FontStyle = "Italic", FontSize = "48", Color = "#225522" }; InitializeComponent(); }   Now instead of chaining to set all different properties you can just pass one of the jQueryObjectCss objects to the Css() method. In this case all <LI></LI> elements are set to match this object.   jQuery.Select("li").Css(CssObject1); When using the jQueryObjectCss objects chaining is still possible. In the following example all headers are given a blue backgroundcolor and the last is set to match CssObject2.   jQuery.Select(":header").Css(new jQueryObjectCss{BackgroundColor = "Blue"}) .Eq(-1).Css(CssObject2);   Part 3: The fun stuff Having Silverlight call JavaScript and than having JavaScript to call Silverlight requires a lot of plumbing code. Everything has to be registered and strings are passed back and forth to execute the JavaScript. jLight makes this kind of stuff so easy, it becomes fun to use. In a lot of situations jQuery can call a function to decide what to do, setting a style class based on complex expressions for example. jLight can do the same, but the callback methods are defined in Silverlight. This example calls the function() method for each <LI></LI> element. The callback method has to take a jQueryObject, an integer and a string as parameters. In this case jLight differs a bit from the actual jQuery implementation. jQuery uses only the index and the className parameters. A jQueryObject is added to make it simpler to access the attributes and properties of the element. If the text of the listitem starts with a ‘D’ or an ‘M’ the class is set. Otherwise null is returned and nothing happens.   private void button1_Click(object sender, RoutedEventArgs e) { jQuery.Select("li").AddClass(function); }   private string function(jQueryObject obj, int index, string className) { if (obj.Text[0] == 'D' || obj.Text[0] == 'M') return "demostyle"; return null; }   The last thing I would like to demonstrate uses even more Silverlight and less jLight, but demonstrates the power of the combination. Animating a style property using a Storyboard with easing functions. First a dependency property is defined. In this case it is a double named Intensity. By handling the changed event the color is set using jQuery.   public double Intensity { get { return (double)GetValue(IntensityProperty); } set { SetValue(IntensityProperty, value); } }   public static readonly DependencyProperty IntensityProperty = DependencyProperty.Register("Intensity", typeof(double), typeof(Demo3), new PropertyMetadata(0.0, IntensityChanged));   private static void IntensityChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) { var i = (byte)(double)e.NewValue; jQuery.Select("span").Css("color", string.Format("#{0:X2}{0:X2}{0:X2}", i)); }   An animation has to be created. This code defines a Storyboard with one keyframe that uses a bounce ease as an easing function. The animation is set to target the Intensity dependency property defined earlier.   private Storyboard CreateAnimation(double value) { Storyboard storyboard = new Storyboard(); var da = new DoubleAnimationUsingKeyFrames(); var d = new EasingDoubleKeyFrame { EasingFunction = new BounceEase(), KeyTime = KeyTime.FromTimeSpan(TimeSpan.FromSeconds(1.0)), Value = value }; da.KeyFrames.Add(d); Storyboard.SetTarget(da, this); Storyboard.SetTargetProperty(da, new PropertyPath(Demo3.IntensityProperty)); storyboard.Children.Add(da); return storyboard; }   Initially the Intensity is set to 128 which results in a gray color. When one of the buttons is pressed, a new animation is created an played. One to animate to black, and one to animate to white.   public Demo3() { InitializeComponent(); Intensity = 128; }   private void button2_Click(object sender, RoutedEventArgs e) { CreateAnimation(255).Begin(); }   private void button3_Click(object sender, RoutedEventArgs e) { CreateAnimation(0).Begin(); }   Conclusion As you can see jLight can make the life of a Silverlight developer a lot easier when accessing the DOM. Almost all jQuery functions that are defined in jLight use the same constructions as described above. I’ve tried to stay as close as possible to the real jQuery. Having JavaScript perform callbacks to Silverlight using jLight will be described in more detail in a future tutorial about AJAX or eventing.

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  • Brendan Gregg's "Systems Performance: Enterprise and the Cloud"

    - by user12608550
    Long ago, the prerequisite UNIX performance book was Adrian Cockcroft's 1994 classic, Sun Performance and Tuning: Sparc & Solaris, later updated in 1998 as Java and the Internet. As Solaris evolved to include the invaluable DTrace observability features, new essential performance references have been published, such as Solaris Performance and Tools: DTrace and MDB Techniques for Solaris 10 and OpenSolaris (2006)  by McDougal, Mauro, and Gregg, and DTrace: Dynamic Tracing in Oracle Solaris, Mac OS X and FreeBSD (2011), also by Mauro and Gregg. Much has occurred in Solaris Land since those books appeared, notably Oracle's acquisition of Sun Microsystems in 2010 and the demise of the OpenSolaris community. But operating system technologies have continued to improve markedly in recent years, driven by stunning advances in multicore processor architecture, virtualization, and the massive scalability requirements of cloud computing. A new performance reference was needed, and I eagerly waited for something that thoroughly covered modern, distributed computing performance issues from the ground up. Well, there's a new classic now, authored yet again by Brendan Gregg, former Solaris kernel engineer at Sun and now Lead Performance Engineer at Joyent. Systems Performance: Enterprise and the Cloud is a modern, very comprehensive guide to general system performance principles and practices, as well as a highly detailed reference for specific UNIX and Linux observability tools used to examine and diagnose operating system behaviour.  It provides thorough definitions of terms, explains performance diagnostic Best Practices and "Worst Practices" (called "anti-methods"), and covers key observability tools including DTrace, SystemTap, and all the traditional UNIX utilities like vmstat, ps, iostat, and many others. The book focuses on operating system performance principles and expands on these with respect to Linux (Ubuntu, Fedora, and CentOS are cited), and to Solaris and its derivatives [1]; it is not directed at any one OS so it is extremely useful as a broad performance reference. The author goes beyond the intricacies of performance analysis and shows how to interpret and visualize statistical information gathered from the observability tools.  It's often difficult to extract understanding from voluminous rows of text output, and techniques are provided to assist with summarizing, visualizing, and interpreting the performance data. Gregg includes myriad useful references from the system performance literature, including a "Who's Who" of contributors to this great body of diagnostic tools and methods. This outstanding book should be required reading for UNIX and Linux system administrators as well as anyone charged with diagnosing OS performance issues.  Moreover, the book can easily serve as a textbook for a graduate level course in operating systems [2]. [1] Solaris 11, of course, and Joyent's SmartOS (developed from OpenSolaris) [2] Gregg has taught system performance seminars for many years; I have also taught such courses...this book would be perfect for the OS component of an advanced CS curriculum.

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  • More Fun with C# Iterators and Generators

    - by James Michael Hare
    In my last post, I talked quite a bit about iterators and how they can be really powerful tools for filtering a list of items down to a subset of items.  This had both pros and cons over returning a full collection, which, in summary, were:   Pros: If traversal is only partial, does not have to visit rest of collection. If evaluation method is costly, only incurs that cost on elements visited. Adds little to no garbage collection pressure.    Cons: Very slight performance impact if you know caller will always consume all items in collection. And as we saw in the last post, that con for the cost was very, very small and only really became evident on very tight loops consuming very large lists completely.    One of the key items to note, though, is the garbage!  In the traditional (return a new collection) method, if you have a 1,000,000 element collection, and wish to transform or filter it in some way, you have to allocate space for that copy of the collection.  That is, say you have a collection of 1,000,000 items and you want to double every item in the collection.  Well, that means you have to allocate a collection to hold those 1,000,000 items to return, which is a lot especially if you are just going to use it once and toss it.   Iterators, though, don't have this problem.  Each time you visit the node, it would return the doubled value of the node (in this example) and not allocate a second collection of 1,000,000 doubled items.  Do you see the distinction?  In both cases, we're consuming 1,000,000 items.  But in one case we pass back each doubled item which is just an int (for example's sake) on the stack and in the other case, we allocate a list containing 1,000,000 items which then must be garbage collected.   So iterators in C# are pretty cool, eh?  Well, here's one more thing a C# iterator can do that a traditional "return a new collection" transformation can't!   It can return **unbounded** collections!   I know, I know, that smells a lot like an infinite loop, eh?  Yes and no.  Basically, you're relying on the caller to put the bounds on the list, and as long as the caller doesn't you keep going.  Consider this example:   public static class Fibonacci {     // returns the infinite fibonacci sequence     public static IEnumerable<int> Sequence()     {         int iteration = 0;         int first = 1;         int second = 1;         int current = 0;         while (true)         {             if (iteration++ < 2)             {                 current = 1;             }             else             {                 current = first + second;                 second = first;                 first = current;             }             yield return current;         }     } }   Whoa, you say!  Yes, that's an infinite loop!  What the heck is going on there?  Yes, that was intentional.  Would it be better to have a fibonacci sequence that returns only a specific number of items?  Perhaps, but that wouldn't give you the power to defer the execution to the caller.   The beauty of this function is it is as infinite as the sequence itself!  The fibonacci sequence is unbounded, and so is this method.  It will continue to return fibonacci numbers for as long as you ask for them.  Now that's not something you can do with a traditional method that would return a collection of ints representing each number.  In that case you would eventually run out of memory as you got to higher and higher numbers.  This method, though, never runs out of memory.   Now, that said, you do have to know when you use it that it is an infinite collection and bound it appropriately.  Fortunately, Linq provides a lot of these extension methods for you!   Let's say you only want the first 10 fibonacci numbers:       foreach(var fib in Fibonacci.Sequence().Take(10))     {         Console.WriteLine(fib);     }   Or let's say you only want the fibonacci numbers that are less than 100:       foreach(var fib in Fibonacci.Sequence().TakeWhile(f => f < 100))     {         Console.WriteLine(fib);     }   So, you see, one of the nice things about iterators is their power to work with virtually any size (even infinite) collections without adding the garbage collection overhead of making new collections.    You can also do fun things like this to make a more "fluent" interface for for loops:   // A set of integer generator extension methods public static class IntExtensions {     // Begins counting to inifity, use To() to range this.     public static IEnumerable<int> Every(this int start)     {         // deliberately avoiding condition because keeps going         // to infinity for as long as values are pulled.         for (var i = start; ; ++i)         {             yield return i;         }     }     // Begins counting to infinity by the given step value, use To() to     public static IEnumerable<int> Every(this int start, int byEvery)     {         // deliberately avoiding condition because keeps going         // to infinity for as long as values are pulled.         for (var i = start; ; i += byEvery)         {             yield return i;         }     }     // Begins counting to inifity, use To() to range this.     public static IEnumerable<int> To(this int start, int end)     {         for (var i = start; i <= end; ++i)         {             yield return i;         }     }     // Ranges the count by specifying the upper range of the count.     public static IEnumerable<int> To(this IEnumerable<int> collection, int end)     {         return collection.TakeWhile(item => item <= end);     } }   Note that there are two versions of each method.  One that starts with an int and one that starts with an IEnumerable<int>.  This is to allow more power in chaining from either an existing collection or from an int.  This lets you do things like:   // count from 1 to 30 foreach(var i in 1.To(30)) {     Console.WriteLine(i); }     // count from 1 to 10 by 2s foreach(var i in 0.Every(2).To(10)) {     Console.WriteLine(i); }     // or, if you want an infinite sequence counting by 5s until something inside breaks you out... foreach(var i in 0.Every(5)) {     if (someCondition)     {         break;     }     ... }     Yes, those are kinda play functions and not particularly useful, but they show some of the power of generators and extension methods to form a fluid interface.   So what do you think?  What are some of your favorite generators and iterators?

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  • What is a Long Tail Keyword?

    Did you know that a long tail keyword will out convert a root keyword 9 times out of 10. In this article, I will discuss the reasons why the long tail is a better keyword to chase than the more common methods of chasing the root.

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  • TSQL formatting - a sure fire way to start a conversation.

    - by fatherjack
    There are probably as many opinions on ways to format code as there are people writing code and I am not here to say that any one is better than any other. Well, that isn't true. I am here to say that one way is better than another but this isn't a matter of preference or personal taste, this is an example of where sloppy formatting can cause TSQL to weird and whacky things but following some simple methods can make your code more reliable and more robust when . Take these two pieces of code, ready...(read more)

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  • Keyword Optimization Tips That Work

    As an online marketer or business owner who is advertising and promoting products and services online, one of the significant selling methods you ought to be acquainted with and be aware of is on page keyword optimization. Keyword optimization is an essential part in the SEO process.

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  • Understanding and Benefiting from Code Contracts in .NET 4.0

    One of the fundamental programming challenges is managing state. Chances are you have written dozens and dozens of methods that at the beginning check that certain conditions are met, and that another set of conditions is met when the method returns. With Code Contracts in .NET 4.0, you can make things considerably easier. Read on to learn how.

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  • Oracle redonne un élan au Projet Lambda sur Java 7 et les closures : Interface evolution via "public

    Bonjour, Depuis quelques temps, on n'entendait plus trop parler des Closures et de leur ajout à Java 7. En réponse à David Flanagan qui s'inquiétait récemment du silence d'Oracle et de la stagnation du Project Lambda, Brian Goetz (Oracle) a soumis il y a quelques jours un document de réflexion sur la notion de virtual extension methods permettant d'ajouter sur une interface existante de nouvelles méthodes (avec des implémentations par défaut) sans casser le contrat avec le code existant.

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  • How accurate is "Business logic should be in a service, not in a model"?

    - by Jeroen Vannevel
    Situation Earlier this evening I gave an answer to a question on StackOverflow. The question: Editing of an existing object should be done in repository layer or in service? For example if I have a User that has debt. I want to change his debt. Should I do it in UserRepository or in service for example BuyingService by getting an object, editing it and saving it ? My answer: You should leave the responsibility of mutating an object to that same object and use the repository to retrieve this object. Example situation: class User { private int debt; // debt in cents private string name; // getters public void makePayment(int cents){ debt -= cents; } } class UserRepository { public User GetUserByName(string name){ // Get appropriate user from database } } A comment I received: Business logic should really be in a service. Not in a model. What does the internet say? So, this got me searching since I've never really (consciously) used a service layer. I started reading up on the Service Layer pattern and the Unit Of Work pattern but so far I can't say I'm convinced a service layer has to be used. Take for example this article by Martin Fowler on the anti-pattern of an Anemic Domain Model: There are objects, many named after the nouns in the domain space, and these objects are connected with the rich relationships and structure that true domain models have. The catch comes when you look at the behavior, and you realize that there is hardly any behavior on these objects, making them little more than bags of getters and setters. Indeed often these models come with design rules that say that you are not to put any domain logic in the the domain objects. Instead there are a set of service objects which capture all the domain logic. These services live on top of the domain model and use the domain model for data. (...) The logic that should be in a domain object is domain logic - validations, calculations, business rules - whatever you like to call it. To me, this seemed exactly what the situation was about: I advocated the manipulation of an object's data by introducing methods inside that class that do just that. However I realize that this should be a given either way, and it probably has more to do with how these methods are invoked (using a repository). I also had the feeling that in that article (see below), a Service Layer is more considered as a façade that delegates work to the underlying model, than an actual work-intensive layer. Application Layer [his name for Service Layer]: Defines the jobs the software is supposed to do and directs the expressive domain objects to work out problems. The tasks this layer is responsible for are meaningful to the business or necessary for interaction with the application layers of other systems. This layer is kept thin. It does not contain business rules or knowledge, but only coordinates tasks and delegates work to collaborations of domain objects in the next layer down. It does not have state reflecting the business situation, but it can have state that reflects the progress of a task for the user or the program. Which is reinforced here: Service interfaces. Services expose a service interface to which all inbound messages are sent. You can think of a service interface as a façade that exposes the business logic implemented in the application (typically, logic in the business layer) to potential consumers. And here: The service layer should be devoid of any application or business logic and should focus primarily on a few concerns. It should wrap Business Layer calls, translate your Domain in a common language that your clients can understand, and handle the communication medium between server and requesting client. This is a serious contrast to other resources that talk about the Service Layer: The service layer should consist of classes with methods that are units of work with actions that belong in the same transaction. Or the second answer to a question I've already linked: At some point, your application will want some business logic. Also, you might want to validate the input to make sure that there isn't something evil or nonperforming being requested. This logic belongs in your service layer. "Solution"? Following the guidelines in this answer, I came up with the following approach that uses a Service Layer: class UserController : Controller { private UserService _userService; public UserController(UserService userService){ _userService = userService; } public ActionResult MakeHimPay(string username, int amount) { _userService.MakeHimPay(username, amount); return RedirectToAction("ShowUserOverview"); } public ActionResult ShowUserOverview() { return View(); } } class UserService { private IUserRepository _userRepository; public UserService(IUserRepository userRepository) { _userRepository = userRepository; } public void MakeHimPay(username, amount) { _userRepository.GetUserByName(username).makePayment(amount); } } class UserRepository { public User GetUserByName(string name){ // Get appropriate user from database } } class User { private int debt; // debt in cents private string name; // getters public void makePayment(int cents){ debt -= cents; } } Conclusion All together not much has changed here: code from the controller has moved to the service layer (which is a good thing, so there is an upside to this approach). However this doesn't look like it had anything to do with my original answer. I realize design patterns are guidelines, not rules set in stone to be implemented whenever possible. Yet I have not found a definitive explanation of the service layer and how it should be regarded. Is it a means to simply extract logic from the controller and put it inside a service instead? Is it supposed to form a contract between the controller and the domain? Should there be a layer between the domain and the service layer? And, last but not least: following the original comment Business logic should really be in a service. Not in a model. Is this correct? How would I introduce my business logic in a service instead of the model?

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  • Revision Methodology for Developer Post as Entry Level

    - by Demla Pawan
    I had revised all basic concepts of my computer science ciriculum like: Core Java(basics),SQL(basics),C++(basics),XHTML,PHP(basics),Datastructures(basics) and what I need to do,and How to do, as their may be fault in my preparation methods for revision session's, So can Anybody suggest Methodology to revise those technical things,to which you are not in touch at present, but you can write basic programs or have used 1-2 years ago. And also can U suggest some Quick revision links on Net for various technologies mentioned above.

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  • Pluggable Rules for Entity Framework Code First

    - by Ricardo Peres
    Suppose you want a system that lets you plug custom validation rules on your Entity Framework context. The rules would control whether an entity can be saved, updated or deleted, and would be implemented in plain .NET. Yes, I know I already talked about plugable validation in Entity Framework Code First, but this is a different approach. An example API is in order, first, a ruleset, which will hold the collection of rules: 1: public interface IRuleset : IDisposable 2: { 3: void AddRule<T>(IRule<T> rule); 4: IEnumerable<IRule<T>> GetRules<T>(); 5: } Next, a rule: 1: public interface IRule<T> 2: { 3: Boolean CanSave(T entity, DbContext ctx); 4: Boolean CanUpdate(T entity, DbContext ctx); 5: Boolean CanDelete(T entity, DbContext ctx); 6: String Name 7: { 8: get; 9: } 10: } Let’s analyze what we have, starting with the ruleset: Only has methods for adding a rule, specific to an entity type, and to list all rules of this entity type; By implementing IDisposable, we allow it to be cancelled, by disposing of it when we no longer want its rules to be applied. A rule, on the other hand: Has discrete methods for checking if a given entity can be saved, updated or deleted, which receive as parameters the entity itself and a pointer to the DbContext to which the ruleset was applied; Has a name property for helping us identifying what failed. A ruleset really doesn’t need a public implementation, all we need is its interface. The private (internal) implementation might look like this: 1: sealed class Ruleset : IRuleset 2: { 3: private readonly IDictionary<Type, HashSet<Object>> rules = new Dictionary<Type, HashSet<Object>>(); 4: private ObjectContext octx = null; 5:  6: internal Ruleset(ObjectContext octx) 7: { 8: this.octx = octx; 9: } 10:  11: public void AddRule<T>(IRule<T> rule) 12: { 13: if (this.rules.ContainsKey(typeof(T)) == false) 14: { 15: this.rules[typeof(T)] = new HashSet<Object>(); 16: } 17:  18: this.rules[typeof(T)].Add(rule); 19: } 20:  21: public IEnumerable<IRule<T>> GetRules<T>() 22: { 23: if (this.rules.ContainsKey(typeof(T)) == true) 24: { 25: foreach (IRule<T> rule in this.rules[typeof(T)]) 26: { 27: yield return (rule); 28: } 29: } 30: } 31:  32: public void Dispose() 33: { 34: this.octx.SavingChanges -= RulesExtensions.OnSaving; 35: RulesExtensions.rulesets.Remove(this.octx); 36: this.octx = null; 37:  38: this.rules.Clear(); 39: } 40: } Basically, this implementation: Stores the ObjectContext of the DbContext to which it was created for, this is so that later we can remove the association; Has a collection - a set, actually, which does not allow duplication - of rules indexed by the real Type of an entity (because of proxying, an entity may be of a type that inherits from the class that we declared); Has generic methods for adding and enumerating rules of a given type; Has a Dispose method for cancelling the enforcement of the rules. A (really dumb) rule applied to Product might look like this: 1: class ProductRule : IRule<Product> 2: { 3: #region IRule<Product> Members 4:  5: public String Name 6: { 7: get 8: { 9: return ("Rule 1"); 10: } 11: } 12:  13: public Boolean CanSave(Product entity, DbContext ctx) 14: { 15: return (entity.Price > 10000); 16: } 17:  18: public Boolean CanUpdate(Product entity, DbContext ctx) 19: { 20: return (true); 21: } 22:  23: public Boolean CanDelete(Product entity, DbContext ctx) 24: { 25: return (true); 26: } 27:  28: #endregion 29: } The DbContext is there because we may need to check something else in the database before deciding whether to allow an operation or not. And here’s how to apply this mechanism to any DbContext, without requiring the usage of a subclass, by means of an extension method: 1: public static class RulesExtensions 2: { 3: private static readonly MethodInfo getRulesMethod = typeof(IRuleset).GetMethod("GetRules"); 4: internal static readonly IDictionary<ObjectContext, Tuple<IRuleset, DbContext>> rulesets = new Dictionary<ObjectContext, Tuple<IRuleset, DbContext>>(); 5:  6: private static Type GetRealType(Object entity) 7: { 8: return (entity.GetType().Assembly.IsDynamic == true ? entity.GetType().BaseType : entity.GetType()); 9: } 10:  11: internal static void OnSaving(Object sender, EventArgs e) 12: { 13: ObjectContext octx = sender as ObjectContext; 14: IRuleset ruleset = rulesets[octx].Item1; 15: DbContext ctx = rulesets[octx].Item2; 16:  17: foreach (ObjectStateEntry entry in octx.ObjectStateManager.GetObjectStateEntries(EntityState.Added)) 18: { 19: Object entity = entry.Entity; 20: Type realType = GetRealType(entity); 21:  22: foreach (dynamic rule in (getRulesMethod.MakeGenericMethod(realType).Invoke(ruleset, null) as IEnumerable)) 23: { 24: if (rule.CanSave(entity, ctx) == false) 25: { 26: throw (new Exception(String.Format("Cannot save entity {0} due to rule {1}", entity, rule.Name))); 27: } 28: } 29: } 30:  31: foreach (ObjectStateEntry entry in octx.ObjectStateManager.GetObjectStateEntries(EntityState.Deleted)) 32: { 33: Object entity = entry.Entity; 34: Type realType = GetRealType(entity); 35:  36: foreach (dynamic rule in (getRulesMethod.MakeGenericMethod(realType).Invoke(ruleset, null) as IEnumerable)) 37: { 38: if (rule.CanDelete(entity, ctx) == false) 39: { 40: throw (new Exception(String.Format("Cannot delete entity {0} due to rule {1}", entity, rule.Name))); 41: } 42: } 43: } 44:  45: foreach (ObjectStateEntry entry in octx.ObjectStateManager.GetObjectStateEntries(EntityState.Modified)) 46: { 47: Object entity = entry.Entity; 48: Type realType = GetRealType(entity); 49:  50: foreach (dynamic rule in (getRulesMethod.MakeGenericMethod(realType).Invoke(ruleset, null) as IEnumerable)) 51: { 52: if (rule.CanUpdate(entity, ctx) == false) 53: { 54: throw (new Exception(String.Format("Cannot update entity {0} due to rule {1}", entity, rule.Name))); 55: } 56: } 57: } 58: } 59:  60: public static IRuleset CreateRuleset(this DbContext context) 61: { 62: Tuple<IRuleset, DbContext> ruleset = null; 63: ObjectContext octx = (context as IObjectContextAdapter).ObjectContext; 64:  65: if (rulesets.TryGetValue(octx, out ruleset) == false) 66: { 67: ruleset = rulesets[octx] = new Tuple<IRuleset, DbContext>(new Ruleset(octx), context); 68: 69: octx.SavingChanges += OnSaving; 70: } 71:  72: return (ruleset.Item1); 73: } 74: } It relies on the SavingChanges event of the ObjectContext to intercept the saving operations before they are actually issued. Yes, it uses a bit of dynamic magic! Very handy, by the way! So, let’s put it all together: 1: using (MyContext ctx = new MyContext()) 2: { 3: IRuleset rules = ctx.CreateRuleset(); 4: rules.AddRule(new ProductRule()); 5:  6: ctx.Products.Add(new Product() { Name = "xyz", Price = 50000 }); 7:  8: ctx.SaveChanges(); //an exception is fired here 9:  10: //when we no longer need to apply the rules 11: rules.Dispose(); 12: } Feel free to use it and extend it any way you like, and do give me your feedback! As a final note, this can be easily changed to support plain old Entity Framework (not Code First, that is), if that is what you are using.

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    For a previous project, I was using Backbonejs alongside Django, but I found out that I didn't use many features from Django. So, I am looking for a lighter framework to use underneath a Backbonejs web app. I never used Django built in templates. When I did, it was to set up the initial index page, but that's all. I did use the user management system that Django provided. I used the models.py, but never views.py. I used urls.py to set up which template the user would hit upon visiting the site. I noticed that the two features that I used most from Django was South and Tastypie, and they aren't even included with Django. Particularly, django-tastypie made it easy for me to link up my frontend models to my backend models. It made it easy to JSONify my front end models and send them to Tastypie. Although, I found myself overriding a lot of tastypie's methods for GET, PUT, POST requests, so it became useless. South made it easy to migrate new changes to the database. Although, I had so much trouble with South. Is there a framework with an easier way of handling database modifications than using South? When using South with multiple people, we had the worse time keeping our databases synced. When someone added a new table and pushed their migration to git, the other two people would spend days trying to use South's automatic migration, but it never worked. I liked how Rails had a manual way of migrating databases. Even though I used Tastypie and South a lot, I found myself not actually liking them because I ended up overriding most Tastypie methods for each Resource, and I also had the worst trouble migrating new tables and columns with South. So, I would like a framework that makes that process easier. Part of my problem was that they are too "magical". Which framework should I use? Nodejs or a lighter Python framework? Which works best with my above criteria?

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  • How do you exclude yourself from Google Analytics on your website using cookies?

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    I'm trying to set up an exclusion filter with a browser cookie, so that my own visits to my don't show up in my Google Analytics. I tried 3 different methods and none of them have worked so far. I would like help understanding what I am doing wrong and how I can fix this. Method 1 First, I tried following Google's instructions, http://www.google.com/support/analytics/bin/answer.py?hl=en&answer=55481, for excluding traffic by Cookie Content: Create a new page on your domain, containing the following code: <body onLoad="javascript:pageTracker._setVar('test_value');"> Method 2 Next, when that didn't work, I googled around and found this Google thread, http://www.google.com/support/forum/p/Google%20Analytics/thread?tid=4741f1499823fcd5&hl=en, where the most popular answer says to use a slightly different code: SHS Analytics wrote: <body onLoad="javascript:_gaq.push(['_setVar','test_value']);"> Thank you! This has now set a __utmv cookie containing "test_value", whereas the original: pageTracker._setVar('test_value') (which Google is still recommending) did not manage to do that for me (in Mac Safari 5 and Firefox 3.6.8). So I tried this code, but it didn't work for me. Method 3 Finally, I searched StackOverflow and came across this thread, http://stackoverflow.com/questions/3495270/exclude-my-traffic-from-google-analytics-using-cookie-with-subdomain, which suggests that the following code might work: <script type="text/javascript"> var _gaq = _gaq || []; _gaq.push(['_setVar', 'exclude_me']); _gaq.push(['_setAccount', 'UA-xxxxxxxx-x']); _gaq.push(['_trackPageview']); // etc... </script> This script appeared in the head element in the example, instead of in the onload event of the body like in the previous 2 examples. So I tried this too, but still had no luck with trying to exclude myself from Google Analytics. Re-iterate question So, I tried all 3 methods above with no success. Am I doing something wrong? How can I exclude myself from my Google Analytics using an exclusion cookie for my browser?

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  • Increasing Your Internet Speed

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  • Tips for Novice Web Designers

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