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  • Subterranean IL: Generics and array covariance

    - by Simon Cooper
    Arrays in .NET are curious beasts. They are the only built-in collection types in the CLR, and SZ-arrays (single dimension, zero-indexed) have their own commands and IL syntax. One of their stranger properties is they have a kind of built-in covariance long before generic variance was added in .NET 4. However, this causes a subtle but important problem with generics. First of all, we need to briefly recap on array covariance. SZ-array covariance To demonstrate, I'll tweak the classes I introduced in my previous posts: public class IncrementableClass { public int Value; public virtual void Increment(int incrementBy) { Value += incrementBy; } } public class IncrementableClassx2 : IncrementableClass { public override void Increment(int incrementBy) { base.Increment(incrementBy); base.Increment(incrementBy); } } In the CLR, SZ-arrays of reference types are implicitly convertible to arrays of the element's supertypes, all the way up to object (note that this does not apply to value types). That is, an instance of IncrementableClassx2[] can be used wherever a IncrementableClass[] or object[] is required. When an SZ-array could be used in this fashion, a run-time type check is performed when you try to insert an object into the array to make sure you're not trying to insert an instance of IncrementableClass into an IncrementableClassx2[]. This check means that the following code will compile fine but will fail at run-time: IncrementableClass[] array = new IncrementableClassx2[1]; array[0] = new IncrementableClass(); // throws ArrayTypeMismatchException These checks are enforced by the various stelem* and ldelem* il instructions in such a way as to ensure you can't insert a IncrementableClass into a IncrementableClassx2[]. For the rest of this post, however, I'm going to concentrate on the ldelema instruction. ldelema This instruction pops the array index (int32) and array reference (O) off the stack, and pushes a pointer (&) to the corresponding array element. However, unlike the ldelem instruction, the instruction's type argument must match the run-time array type exactly. This is because, once you've got a managed pointer, you can use that pointer to both load and store values in that array element using the ldind* and stind* (load/store indirect) instructions. As the same pointer can be used for both input and output to the array, the type argument to ldelema must be invariant. At the time, this was a perfectly reasonable restriction, and maintained array type-safety within managed code. However, along came generics, and with it the constrained callvirt instruction. So, what happens when we combine array covariance and constrained callvirt? .method public static void CallIncrementArrayValue() { // IncrementableClassx2[] arr = new IncrementableClassx2[1] ldc.i4.1 newarr IncrementableClassx2 // arr[0] = new IncrementableClassx2(); dup newobj instance void IncrementableClassx2::.ctor() ldc.i4.0 stelem.ref // IncrementArrayValue<IncrementableClass>(arr, 0) // here, we're treating an IncrementableClassx2[] as IncrementableClass[] dup ldc.i4.0 call void IncrementArrayValue<class IncrementableClass>(!!0[],int32) // ... ret } .method public static void IncrementArrayValue<(IncrementableClass) T>( !!T[] arr, int32 index) { // arr[index].Increment(1) ldarg.0 ldarg.1 ldelema !!T ldc.i4.1 constrained. !!T callvirt instance void IIncrementable::Increment(int32) ret } And the result: Unhandled Exception: System.ArrayTypeMismatchException: Attempted to access an element as a type incompatible with the array. at IncrementArrayValue[T](T[] arr, Int32 index) at CallIncrementArrayValue() Hmm. We're instantiating the generic method as IncrementArrayValue<IncrementableClass>, but passing in an IncrementableClassx2[], hence the ldelema instruction is failing as it's expecting an IncrementableClass[]. On features and feature conflicts What we've got here is a conflict between existing behaviour (ldelema ensuring type safety on covariant arrays) and new behaviour (managed pointers to object references used for every constrained callvirt on generic type instances). And, although this is an edge case, there is no general workaround. The generic method could be hidden behind several layers of assemblies, wrappers and interfaces that make it a requirement to use array covariance when calling the generic method. Furthermore, this will only fail at runtime, whereas compile-time safety is what generics were designed for! The solution is the readonly. prefix instruction. This modifies the ldelema instruction to ignore the exact type check for arrays of reference types, and so it lets us take the address of array elements using a covariant type to the actual run-time type of the array: .method public static void IncrementArrayValue<(IncrementableClass) T>( !!T[] arr, int32 index) { // arr[index].Increment(1) ldarg.0 ldarg.1 readonly. ldelema !!T ldc.i4.1 constrained. !!T callvirt instance void IIncrementable::Increment(int32) ret } But what about type safety? In return for ignoring the type check, the resulting controlled mutability pointer can only be used in the following situations: As the object parameter to ldfld, ldflda, stfld, call and constrained callvirt instructions As the pointer parameter to ldobj or ldind* As the source parameter to cpobj In other words, the only operations allowed are those that read from the pointer; stind* and similar that alter the pointer itself are banned. This ensures that the array element we're pointing to won't be changed to anything untoward, and so type safety within the array is maintained. This is a typical example of the maxim that whenever you add a feature to a program, you have to consider how that feature interacts with every single one of the existing features. Although an edge case, the readonly. prefix instruction ensures that generics and array covariance work together and that compile-time type safety is maintained. Tune in next time for a look at the .ctor generic type constraint, and what it means.

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  • 2D Platformer Collision Handling

    - by defender-zone
    Hello, everyone! I am trying to create a 2D platformer (Mario-type) game and I am some having some issues with handling collisions properly. I am writing this game in C++, using SDL for input, image loading, font loading, etcetera. I am also using OpenGL via the FreeGLUT library in conjunction with SDL to display graphics. My method of collision detection is AABB (Axis-Aligned Bounding Box), which is really all I need to start with. What I need is an easy way to both detect which side the collision occurred on and handle the collisions properly. So, basically, if the player collides with the top of the platform, reposition him to the top; if there is a collision to the sides, reposition the player back to the side of the object; if there is a collision to the bottom, reposition the player under the platform. I have tried many different ways of doing this, such as trying to find the penetration depth and repositioning the player backwards by the penetration depth. Sadly, nothing I've tried seems to work correctly. Player movement ends up being very glitchy and repositions the player when I don't want it to. Part of the reason is probably because I feel like this is something so simple but I'm over-thinking it. If anyone thinks they can help, please take a look at the code below and help me try to improve on this if you can. I would like to refrain from using a library to handle this (as I want to learn on my own) or the something like the SAT (Separating Axis Theorem) if at all possible. Thank you in advance for your help! void world1Level1CollisionDetection() { for(int i; i < blocks; i++) { if (de2dCheckCollision(ball,block[i],0.0f,0.0f)==true) { int up = 0; int left = 0; int right = 0; int down = 0; if(ball.coords[0] < block[i].coords[0] && block[i].coords[0] < ball.coords[2] && ball.coords[2] < block[i].coords[2]) { left = 1; } if(block[i].coords[0] < ball.coords[0] && ball.coords[0] < block[i].coords[2] && block[i].coords[2] < ball.coords[2]) { right = 1; } if(ball.coords[1] < block[i].coords[1] && block[i].coords[1] < ball.coords[3] && ball.coords[3] < block[i].coords[3]) { up = 1; } if(block[i].coords[1] < ball.coords[1] && ball.coords[1] < block[i].coords[3] && block[i].coords[3] < ball.coords[3]) { down = 1; } cout << left << ", " << right << ", " << up << ", " << down << ", " << endl; if (left == 1) { ball.coords[0] = block[i].coords[0] - 16.0f; ball.coords[2] = block[i].coords[0] - 0.0f; } if (right == 1) { ball.coords[0] = block[i].coords[2] + 0.0f; ball.coords[2] = block[i].coords[2] + 16.0f; } if (down == 1) { ball.coords[1] = block[i].coords[3] + 0.0f; ball.coords[3] = block[i].coords[3] + 16.0f; } if (up == 1) { ball.yspeed = 0.0f; ball.gravity = 0.0f; ball.coords[1] = block[i].coords[1] - 16.0f; ball.coords[3] = block[i].coords[1] - 0.0f; } } if (de2dCheckCollision(ball,block[i],0.0f,0.0f)==false) { ball.gravity = -0.5f; } } } To explain what some of this code means: The blocks variable is basically an integer that is storing the amount of blocks, or platforms. I am checking all of the blocks using a for loop, and the number that the loop is currently on is represented by integer i. The coordinate system might seem a little weird, so that's worth explaining. coords[0] represents the x position (left) of the object (where it starts on the x axis). coords[1] represents the y position (top) of the object (where it starts on the y axis). coords[2] represents the width of the object plus coords[0] (right). coords[3] represents the height of the object plus coords[1] (bottom). de2dCheckCollision performs an AABB collision detection. Up is negative y and down is positive y, as it is in most games. Hopefully I have provided enough information for someone to help me successfully. If there is something I left out that might be crucial, let me know and I'll provide the necessary information. Finally, for anyone who can help, providing code would be very helpful and much appreciated. Thank you again for your help!

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  • How are realistic 3D faces created and animated in video games?

    - by Anton
    I'm interested in being able to create realistic faces and facial expressions for the 3D characters of a game I'm working on. Think something similar to the dialog scenes in games like Mass Effect. Unfortunately I'm not sure where to begin. I'm sure the faces/animations are created through 3D Modeling software, but otherwise I am lost. Do facial animations use the same "bones" that normal body animation uses? Is there any preferred 3D software for realistic faces and animations? Is there a preferred format to export these faces and animations in?

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  • UML Class Diagram: Abstract or Interface?

    - by J Smith
    I am modeling a class diagram and have spotted an opportunity to simplify it slightly. What I want to know is, would this it be better to implement an abstract class or an interface? The scenario is this, I have the classes: Artist Genre Album Song All of which share the methods getName, setName, and getCount (playcount that is). Would it be best to create an abstract 'Music' class with the aforementioned abstract methods, or should I create an interface, since the classes that implement the interface have to include all of the interface's methods (I think, correct me if I'm wrong). I hope I've given enough detail, please ask questions if I haven't. Thanks!

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  • Resources for popular domain models

    - by Songo
    I have come across many situations where I had to build a system for a library or a clinic or other popular domains. The thing is a domain model for a library was probably done 1000 times already with different level of details of course. Here is an example. Is there a popular website or community where one can find ready made domain models for popular systems? The whole purpose I'm trying to achieve is to quickly get a grasp of the domain I'm modeling and customize it to my needs. Re-inventing the wheel seems really absurd when the same system might have been modeled properly previously. Note I know Google might sound like the perfect source, but there is a repository out there that people can post there models, so that others can share them.

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  • Oracle CRM On Demand Release 24 is Generally Available

    - by Richard Lefebvre
    Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 We are pleased to announce that Oracle CRM On Demand Release 24 is Generally Available as of October 25, 2013 Get smarter, more productive and the best value with Oracle CRM On Demand Release 24. Oracle CRM On Demand continues to be the most complete Software-as-a-Service (SaaS) CRM solution available. Now, with Release 24, organizations of all types and sizes benefit from actionable insight anywhere, anytime, as well as key enhancements in mobility, embedded social, analytics, integration and extensibility, and ease of use.Next Generation Mobile and Desktop Solutions : Oracle CRM On Demand Release 24 offers a complete set of mobile and desktop solutions that improve productivity by enabling reps to access and update information anywhere, anytime. Capabilities include: Oracle CRM On Demand Disconnected Mobile Sales (DMS) – A disconnected native iPad solution, DMS has been further streamlined mobile sales process by adding Structured Product Messaging to record brand specific call objectives, enhancements in HTML5 eDetailing including message response tracking and improvements in administration and configuration such as more field management options for read only fields, role management and enhanced logging. Oracle CRM On Demand Connected Mobile Sales. This add-on mobile service provides a configurable mobile solution on iOS, BlackBerry and now Android devices. You can access data from CRM On Demand in real time with a rich, native user experience, that is comfortable and familiar to current iOS, BlackBerry and Android users. New features also include Single Sign On to enhance security for mobile users.  Oracle CRM On Demand Desktop: This application centralizes essential CRM information in the familiar Microsoft Outlook environment,increasing user adoption and decreasing training costs. Users can manage CRM data while disconnected, then synchronize bi-directionally when they are back on the network. New in Oracle CRM On Demand Desktop Version 3 is the ability to synchronize by Books of Business, and improved Online Lookup. Mobile Browser Support: The following mobile device browsers are now supported: Apple iPhone, Apple iPad, Windows 8 Tablets, and Google Android. Leverage the Social Enterprise Engaging customers via social channels is rapidly becoming a significant key to enhanced customer experience as it provides proactive customer service, targeted messaging and greater intimacy throughout the entire customer lifecycle. Listening to customers on the social channels can identify a customers’ sphere of influence and the real value they bring to their organization, or the impact they can have on the opportunity. Servicing the customer’s need is the first step towards loyalty to a brand, integrating with social channels allows us to maximize brand affinity and virally expand customer engagements thus increasing revenue. Oracle CRM On Demand is leveraging the Social Enterprise through its integration with Oracle’s Social Relationship Management (SRM) product suite by providing out-of-the-box integration with Social Engagement and Monitoring (SEM), Social Marketing (SM) and Oracle Social Network (OSN). With Oracle CRM On Demand Release 24, users are able to create a service request from a social post via SEM and have leads entered on a SM lead form automatically entered into Oracle CRM On Demand along with the campaign, streamlining the lead qualification process. Get Smarter with Actionable Insight The difference between making good decisions and great decisions depends heavily upon the quality, structure, and availability of information at hand. Oracle CRM On Demand Release 24 expands upon its industry-leading analytics capabilities to provide greater business insight than ever before. New capabilities include flexible permissions on analytics reports folders, allowing for read only access to reports, and additional field and object coverage. Get More Productive with Powerful Tools Oracle CRM On Demand Release 24 introduces a new set of powerful capabilities designed to maximize productivity. A significant new feature for customizing Oracle CRM On Demand is a JavaScript API. The JS API allows customers to add new buttons, suppress existing buttons and even change what happens when a user clicks an existing button. Other usability enhancements, such as personalized related information applets, extended case insensitive search provide users with better, more intuitive, experience. Additional privileges for viewing private activities and notes allow administrators to reassign records as needed, and Custom Object management. Workflow has been added to the Order Item object; and now tasks can be assigned to a relative user, such as an Account Owner, allowing more complex business processes to be automated and adhered to. Get the Best Value Oracle CRM On Demand delivers unprecedented value with the broadest set of capabilities from a single-provider solution, the industry’s lowest total cost of ownership, the most on-demand deployment options, the deepest CRM expertise and experience of any CRM provider, and the most secure CRM in the cloud. With Release 24, Oracle CRM On Demand now includes even more enterprise-grade security, integration, and extensibility features, along with enhanced industry editions to save you time and money. New features include: Business Process Administration: A new privilege has been added that allows administrators to override a Business Process Administration rule.This privilege permits users to edit a locked record, or unlock a record, in the event of a material change that needs to be reflected per corporatepolicy. Additionally, the Products Detailed object has been added to Business Process Administration, enabling record locking and logic to be applied. Expanded Integration: Oracle continues to improve Web Services each release, by adding more object coverage enabling customers and partners to easily integrate with CRM On Demand. Bottom Line Oracle CRM On Demand Release 24 enables organizations to get smarter, get more productive, and get the best value, period. For more information on Oracle CRM On Demand Release 24, please visit oracle.com/crmondemand

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  • How to Play Classic Arcade Games On Your PC

    - by Jason Fitzpatrick
    New games with their fancy textures, 3D modeling, and immersive environments have their charm, sure, but what if you crave some old-school arcade gaming? Read on to see how you can turn your computer into an virtual arcade cabinet. Vintage games ran on hardware significantly less powerful than that found in modern desktop computers. With the right software, a joystick or two (if you want to make experience feel more authentic), and a little digging online to find your favorite games, it’s easy to play the arcade hits of your childhood. How to Play Classic Arcade Games On Your PC How to Use an Xbox 360 Controller On Your Windows PC Download the Official How-To Geek Trivia App for Windows 8

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  • Oracle University Nouveaux cours (Week 10)

    - by swalker
    Parmi les nouveautés d’Oracle Université de ce mois-ci, vous trouverez : Database RAC & Grid Infrastructure for Oracle Solaris System Administration (1 day) Oracle Database 11g: Performance Tuning (Training On Demand) Development Tools Oracle Database: Program with PL/SQL (Training On Demand) MySQL MySQL for Database Administrators (Training On Demand) Fusion Middleware Oracle SOA Suite 11g : Concepts de base (3 days) Oracle WebCenter Portal 11g: Build Portals With Spaces (3 days) Oracle WebCenter Content 11g: Site Studio Essentials (5 days) Oracle BPM 11g Modeling (3 days) Business Intelligence & Datawarehousing Oracle BI 11g : Mise à niveau et nouvelles fonctionnalités (2 days) Oracle BI Applications 7.9.6: Implementation for Oracle EBS (4 days) Oracle BI Applications 7.9.6: Implementation for Siebel CRM (4 days) Oracle BI 11g R1: Build Repositories (Training on Demand) Fusion Applications Fusion Applications: Extend Applications with ADF (5 days) E-Business Suite R12.x Extend Oracle Applications: Building OA Framework Applications (Training On Demand) PeopleSoft PeopleSoft Integration Tools Rel 8.50 (Training On Demand) Contacter l’équipe locale d’Oracle University pour toute information et dates de cours.

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  • 3d environments and managing them on iOS

    - by alJaree
    I would like to start learning 3d game development and currently only develop 2d games. A few basic questions I am interested in are: What is used to create the 3d environments? Are they all done in e.g. Maya, Lightwave, 3d modeling software? What is the output format for these models and how are they manipulated in iOS? Is it all done using openGL(GL ES on iOS)? e.g a monster needs to be spawned in the game world. What coordinates are used? Are the concepts the same as 2d in terms of collision on the coordinates and movement on the coordinates of the game world? How are 3d games managed in iOS on the low available memory. (e.g. FPS games) Lastly, Can someone please recommend a good book that is up to date and can be applied to todays techniques. Thanks

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  • Automated architecture validation

    - by P.Brian.Mackey
    I am aware of the fact that TFS 2010 ultimate edition can create and validate architecture diagrams. For example, I can create a new modeling project add Layer Diagram Add Layer called View Add BL Layer Add DL layer. Then I can validate this architecture as part of the build process when someone tries to check code into TFS. In other words, if the View references the DL then the compilation process will fail and the checkin will not be allowed. For those without an MSDN ultimate license, can FxCop or some 3rd party utility be used to validate architecture in an automated fashion? I prefer a TFS install-able plugin, but a local VS plugin will do.

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  • Advisor Webcast: Integrating DRM with EPMA

    - by THE
    Leave out your shoes early this year!On December 5th Saint Nicolas has something to put into them... Another Advisor Webcast is on: This time it is Matt Lontchar presenting the setup and use of Data Relationship Modeling ( DRM ) with Hyperion EPMA (to be then used with Planning and or HFM) In this one-hour session he will demonstrate the setup and configuration of a Data Relationship Management application for chart of accounts management with Oracle General Ledger and dimension management for Oracle EPM System applications such as Hyperion Financial Management and Hyperion Planning. Key Points will be: Configuring Data Relationship Management for Oracle GL and EPM Architect integration Configuring Hyperion Foundation Services (Weblogic, Web Services Manager, Shared Services) Deploying and configuring the DRM Web Service Setting up Oracle General Ledger for DRM integration Configuring EPM Architect for DRM integration So - treat yourself for some pre-season "chocolate" and join in on this webcast. You find all relevant information on Doc ID 1504283.1 or via the Advsior Webcast Schedule Note  Doc ID 740966.1 Or simply go directly to the registration site at Webex: https://oracleaw.webex.com/oracleaw/onstage/g.php?d=596766085&t=a

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  • Where can I find Cinema4D for game development tutorials ?

    - by George Profenza
    Hi, I started to learn Cinema 4D. I've noticed it's really easy to use for motion graphics, but I want to use it for modeling for games/realtime 3d engines. Before I used 3dsmax and it was easy to estimate how a model would look/behave in a 3d engine. The two main things I did was displaying Polygon triangles and displaying the Polygon Count. I've found the Total Polygons tick in HUD settings in Cinema 4D, but I can't find any display mode that will show triangles. Is there there a way to display triangle faces/not quads in Cinema4D ? If so how ? There is a Triangulate function, but I'd rather not Triangulate/Untriangulate all the time, especially since it's converting back and forth between the two doesn't always produce the same result. I imagine I'm asking for old school techniques, but I plan to use these to make low poly models for web(canvas/webGL) and mobile.

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  • ASP.NET MVC 3 Hosting :: How to Deploy Web Apps Using ASP.NET MVC 3, Razor and EF Code First - Part II

    - by mbridge
    In previous post, I have discussed on how to work with ASP.NET MVC 3 and EF Code First for developing web apps. In this post, I will demonstrate on working with domain entity with deep object graph, Service Layer and View Models and will also complete the rest of the demo application. In the previous post, we have done CRUD operations against Category entity and this post will be focus on Expense entity those have an association with Category entity. Domain Model Category Entity public class Category   {       public int CategoryId { get; set; }       [Required(ErrorMessage = "Name Required")]       [StringLength(25, ErrorMessage = "Must be less than 25 characters")]       public string Name { get; set;}       public string Description { get; set; }       public virtual ICollection<Expense> Expenses { get; set; }   } Expense Entity public class Expense     {                public int ExpenseId { get; set; }                public string  Transaction { get; set; }         public DateTime Date { get; set; }         public double Amount { get; set; }         public int CategoryId { get; set; }         public virtual Category Category { get; set; }     } We have two domain entities - Category and Expense. A single category contains a list of expense transactions and every expense transaction should have a Category. Repository class for Expense Transaction Let’s create repository class for handling CRUD operations for Expense entity public class ExpenseRepository : RepositoryBase<Expense>, IExpenseRepository     {     public ExpenseRepository(IDatabaseFactory databaseFactory)         : base(databaseFactory)         {         }                } public interface IExpenseRepository : IRepository<Expense> { } Service Layer If you are new to Service Layer, checkout Martin Fowler's article Service Layer . According to Martin Fowler, Service Layer defines an application's boundary and its set of available operations from the perspective of interfacing client layers. It encapsulates the application's business logic, controlling transactions and coordinating responses in the implementation of its operations. Controller classes should be lightweight and do not put much of business logic onto it. We can use the service layer as the business logic layer and can encapsulate the rules of the application. Let’s create a Service class for coordinates the transaction for Expense public interface IExpenseService {     IEnumerable<Expense> GetExpenses(DateTime startDate, DateTime ednDate);     Expense GetExpense(int id);             void CreateExpense(Expense expense);     void DeleteExpense(int id);     void SaveExpense(); } public class ExpenseService : IExpenseService {     private readonly IExpenseRepository expenseRepository;            private readonly IUnitOfWork unitOfWork;     public ExpenseService(IExpenseRepository expenseRepository, IUnitOfWork unitOfWork)     {                  this.expenseRepository = expenseRepository;         this.unitOfWork = unitOfWork;     }     public IEnumerable<Expense> GetExpenses(DateTime startDate, DateTime endDate)     {         var expenses = expenseRepository.GetMany(exp => exp.Date >= startDate && exp.Date <= endDate);         return expenses;     }     public void CreateExpense(Expense expense)     {         expenseRepository.Add(expense);         unitOfWork.Commit();     }     public Expense GetExpense(int id)     {         var expense = expenseRepository.GetById(id);         return expense;     }     public void DeleteExpense(int id)     {         var expense = expenseRepository.GetById(id);         expenseRepository.Delete(expense);         unitOfWork.Commit();     }     public void SaveExpense()     {         unitOfWork.Commit();     } } View Model for Expense Transactions In real world ASP.NET MVC applications, we need to design model objects especially for our views. Our domain objects are mainly designed for the needs for domain model and it is representing the domain of our applications. On the other hand, View Model objects are designed for our needs for views. We have an Expense domain entity that has an association with Category. While we are creating a new Expense, we have to specify that in which Category belongs with the new Expense transaction. The user interface for Expense transaction will have form fields for representing the Expense entity and a CategoryId for representing the Category. So let's create view model for representing the need for Expense transactions. public class ExpenseViewModel {     public int ExpenseId { get; set; }       [Required(ErrorMessage = "Category Required")]     public int CategoryId { get; set; }       [Required(ErrorMessage = "Transaction Required")]     public string Transaction { get; set; }       [Required(ErrorMessage = "Date Required")]     public DateTime Date { get; set; }       [Required(ErrorMessage = "Amount Required")]     public double Amount { get; set; }       public IEnumerable<SelectListItem> Category { get; set; } } The ExpenseViewModel is designed for the purpose of View template and contains the all validation rules. It has properties for mapping values to Expense entity and a property Category for binding values to a drop-down for list values of Category. Create Expense transaction Let’s create action methods in the ExpenseController for creating expense transactions public ActionResult Create() {     var expenseModel = new ExpenseViewModel();     var categories = categoryService.GetCategories();     expenseModel.Category = categories.ToSelectListItems(-1);     expenseModel.Date = DateTime.Today;     return View(expenseModel); } [HttpPost] public ActionResult Create(ExpenseViewModel expenseViewModel) {                      if (!ModelState.IsValid)         {             var categories = categoryService.GetCategories();             expenseViewModel.Category = categories.ToSelectListItems(expenseViewModel.CategoryId);             return View("Save", expenseViewModel);         }         Expense expense=new Expense();         ModelCopier.CopyModel(expenseViewModel,expense);         expenseService.CreateExpense(expense);         return RedirectToAction("Index");              } In the Create action method for HttpGet request, we have created an instance of our View Model ExpenseViewModel with Category information for the drop-down list and passing the Model object to View template. The extension method ToSelectListItems is shown below public static IEnumerable<SelectListItem> ToSelectListItems(         this IEnumerable<Category> categories, int  selectedId) {     return           categories.OrderBy(category => category.Name)                 .Select(category =>                     new SelectListItem                     {                         Selected = (category.CategoryId == selectedId),                         Text = category.Name,                         Value = category.CategoryId.ToString()                     }); } In the Create action method for HttpPost, our view model object ExpenseViewModel will map with posted form input values. We need to create an instance of Expense for the persistence purpose. So we need to copy values from ExpenseViewModel object to Expense object. ASP.NET MVC futures assembly provides a static class ModelCopier that can use for copying values between Model objects. ModelCopier class has two static methods - CopyCollection and CopyModel.CopyCollection method will copy values between two collection objects and CopyModel will copy values between two model objects. We have used CopyModel method of ModelCopier class for copying values from expenseViewModel object to expense object. Finally we did a call to CreateExpense method of ExpenseService class for persisting new expense transaction. List Expense Transactions We want to list expense transactions based on a date range. So let’s create action method for filtering expense transactions with a specified date range. public ActionResult Index(DateTime? startDate, DateTime? endDate) {     //If date is not passed, take current month's first and last dte     DateTime dtNow;     dtNow = DateTime.Today;     if (!startDate.HasValue)     {         startDate = new DateTime(dtNow.Year, dtNow.Month, 1);         endDate = startDate.Value.AddMonths(1).AddDays(-1);     }     //take last date of start date's month, if end date is not passed     if (startDate.HasValue && !endDate.HasValue)     {         endDate = (new DateTime(startDate.Value.Year, startDate.Value.Month, 1)).AddMonths(1).AddDays(-1);     }     var expenses = expenseService.GetExpenses(startDate.Value ,endDate.Value);     //if request is Ajax will return partial view     if (Request.IsAjaxRequest())     {         return PartialView("ExpenseList", expenses);     }     //set start date and end date to ViewBag dictionary     ViewBag.StartDate = startDate.Value.ToShortDateString();     ViewBag.EndDate = endDate.Value.ToShortDateString();     //if request is not ajax     return View(expenses); } We are using the above Index Action method for both Ajax requests and normal requests. If there is a request for Ajax, we will call the PartialView ExpenseList. Razor Views for listing Expense information Let’s create view templates in Razor for showing list of Expense information ExpenseList.cshtml @model IEnumerable<MyFinance.Domain.Expense>   <table>         <tr>             <th>Actions</th>             <th>Category</th>             <th>                 Transaction             </th>             <th>                 Date             </th>             <th>                 Amount             </th>         </tr>       @foreach (var item in Model) {              <tr>             <td>                 @Html.ActionLink("Edit", "Edit",new { id = item.ExpenseId })                 @Ajax.ActionLink("Delete", "Delete", new { id = item.ExpenseId }, new AjaxOptions { Confirm = "Delete Expense?", HttpMethod = "Post", UpdateTargetId = "divExpenseList" })             </td>              <td>                 @item.Category.Name             </td>             <td>                 @item.Transaction             </td>             <td>                 @String.Format("{0:d}", item.Date)             </td>             <td>                 @String.Format("{0:F}", item.Amount)             </td>         </tr>          }       </table>     <p>         @Html.ActionLink("Create New Expense", "Create") |         @Html.ActionLink("Create New Category", "Create","Category")     </p> Index.cshtml @using MyFinance.Helpers; @model IEnumerable<MyFinance.Domain.Expense> @{     ViewBag.Title = "Index"; }    <h2>Expense List</h2>    <script src="@Url.Content("~/Scripts/jquery.unobtrusive-ajax.min.js")" type="text/javascript"></script> <script src="@Url.Content("~/Scripts/jquery-ui.js")" type="text/javascript"></script> <script src="@Url.Content("~/Scripts/jquery.ui.datepicker.js")" type="text/javascript"></script> <link href="@Url.Content("~/Content/jquery-ui-1.8.6.custom.css")" rel="stylesheet" type="text/css" />      @using (Ajax.BeginForm(new AjaxOptions{ UpdateTargetId="divExpenseList", HttpMethod="Get"})) {     <table>         <tr>         <td>         <div>           Start Date: @Html.TextBox("StartDate", Html.Encode(String.Format("{0:mm/dd/yyyy}", ViewData["StartDate"].ToString())), new { @class = "ui-datepicker" })         </div>         </td>         <td><div>            End Date: @Html.TextBox("EndDate", Html.Encode(String.Format("{0:mm/dd/yyyy}", ViewData["EndDate"].ToString())), new { @class = "ui-datepicker" })          </div></td>          <td> <input type="submit" value="Search By TransactionDate" /></td>         </tr>     </table>         }   <div id="divExpenseList">             @Html.Partial("ExpenseList", Model)     </div> <script type="text/javascript">     $().ready(function () {         $('.ui-datepicker').datepicker({             dateFormat: 'mm/dd/yy',             buttonImage: '@Url.Content("~/Content/calendar.gif")',             buttonImageOnly: true,             showOn: "button"         });     }); </script> Ajax search functionality using Ajax.BeginForm The search functionality of Index view is providing Ajax functionality using Ajax.BeginForm. The Ajax.BeginForm() method writes an opening <form> tag to the response. You can use this method in a using block. In that case, the method renders the closing </form> tag at the end of the using block and the form is submitted asynchronously by using JavaScript. The search functionality will call the Index Action method and this will return partial view ExpenseList for updating the search result. We want to update the response UI for the Ajax request onto divExpenseList element. So we have specified the UpdateTargetId as "divExpenseList" in the Ajax.BeginForm method. Add jQuery DatePicker Our search functionality is using a date range so we are providing two date pickers using jQuery datepicker. You need to add reference to the following JavaScript files to working with jQuery datepicker. - jquery-ui.js - jquery.ui.datepicker.js For theme support for datepicker, we can use a customized CSS class. In our example we have used a CSS file “jquery-ui-1.8.6.custom.css”. For more details about the datepicker component, visit jquery UI website at http://jqueryui.com/demos/datepicker . In the jQuery ready event, we have used following JavaScript function to initialize the UI element to show date picker. <script type="text/javascript">     $().ready(function () {         $('.ui-datepicker').datepicker({             dateFormat: 'mm/dd/yy',             buttonImage: '@Url.Content("~/Content/calendar.gif")',             buttonImageOnly: true,             showOn: "button"         });     }); </script> Summary In this two-part series, we have created a simple web application using ASP.NET MVC 3 RTM, Razor and EF Code First CTP 5. I have demonstrated patterns and practices  such as Dependency Injection, Repository pattern, Unit of Work, ViewModel and Service Layer. My primary objective was to demonstrate different practices and options for developing web apps using ASP.NET MVC 3 and EF Code First. You can implement these approaches in your own way for building web apps using ASP.NET MVC 3. I will refactor this demo app on later time.

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  • Is there a quasi-standard set of attributes to annotate thread safety, immutability etc.?

    - by Eugene Beresovksy
    Except for a blog post here and there, describing the custom attributes someone created, but that do not seem to get any traction - like one describing how to enforce immutability, another one on Documenting Thread Safety, modeling the attributes after JCIP annotations - is there any standard emerging? Anything MS might be planning for the future? This is something that should be standard, if there's to be any chance of interoperability between libraries concurrency-wise. Both for documentation purposes, and also to feed static / dynamic test tools. If MS isn't doing anything in that direction, it could be done on CodePlex - but I couldn't find anything there, either. <opinion>Concurrency and thread safety are really hard in imperative and object-languages like C# and Java, we should try to tame it, until we hopefully switch to more appropriate languages.</opinion>

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  • Thread.Interrupt Is Evil

    - by Alois Kraus
    Recently I have found an interesting issue with Thread.Interrupt during application shutdown. Some application was crashing once a week and we had not really a clue what was the issue. Since it happened not very often it was left as is until we have got some memory dumps during the crash. A memory dump usually means WindDbg which I really like to use (I know I am one of the very few fans of it).  After a quick analysis I did find that the main thread already had exited and the thread with the crash was stuck in a Monitor.Wait. Strange Indeed. Running the application a few thousand times under the debugger would potentially not have shown me what the reason was so I decided to what I call constructive debugging. I did create a simple Console application project and try to simulate the exact circumstances when the crash did happen from the information I have via memory dump and source code reading. The thread that was  crashing was actually MS code from an old version of the Microsoft Caching Application Block. From reading the code I could conclude that the main thread did call the Dispose method on the CacheManger class which did call Thread.Interrupt on the cache scavenger thread which was just waiting for work to do. My first version of the repro looked like this   static void Main(string[] args) { Thread t = new Thread(ThreadFunc) { IsBackground = true, Name = "Test Thread" }; t.Start(); Console.WriteLine("Interrupt Thread"); t.Interrupt(); } static void ThreadFunc() { while (true) { object value = Dequeue(); // block until unblocked or awaken via ThreadInterruptedException } } static object WaitObject = new object(); static object Dequeue() { object lret = "got value"; try { lock (WaitObject) { } } catch (ThreadInterruptedException) { Console.WriteLine("Got ThreadInterruptException"); lret = null; } return lret; } I do start a background thread and call Thread.Interrupt on it and then directly let the application terminate. The thread in the meantime does plenty of Monitor.Enter/Leave calls to simulate work on it. This first version did not crash. So I need to dig deeper. From the memory dump I did know that the finalizer thread was doing just some critical finalizers which were closing file handles. Ok lets add some long running finalizers to the sample. class FinalizableObject : CriticalFinalizerObject { ~FinalizableObject() { Console.WriteLine("Hi we are waiting to finalize now and block the finalizer thread for 5s."); Thread.Sleep(5000); } } class Program { static void Main(string[] args) { FinalizableObject fin = new FinalizableObject(); Thread t = new Thread(ThreadFunc) { IsBackground = true, Name = "Test Thread" }; t.Start(); Console.WriteLine("Interrupt Thread"); t.Interrupt(); GC.KeepAlive(fin); // prevent finalizing it too early // After leaving main the other thread is woken up via Thread.Abort // while we are finalizing. This causes a stackoverflow in the CLR ThreadAbortException handling at this time. } With this changed Main method and a blocking critical finalizer I did get my crash just like the real application. The funny thing is that this is actually a CLR bug. When the main method is left the CLR does suspend all threads except the finalizer thread and declares all objects as garbage. After the normal finalizers were called the critical finalizers are executed to e.g. free OS handles (usually). Remember that I did call Thread.Interrupt as one of the last methods in the Main method. The Interrupt method is actually asynchronous and does wake a thread up and throws a ThreadInterruptedException only once unlike Thread.Abort which does rethrow the exception when an exception handling clause is left. It seems that the CLR does not expect that a frozen thread does wake up again while the critical finalizers are executed. While trying to raise a ThreadInterrupedException the CLR goes down with an stack overflow. Ups not so nice. Why has this nobody noticed for years is my next question. As it turned out this error does only happen on the CLR for .NET 4.0 (x86 and x64). It does not show up in earlier or later versions of the CLR. I have reported this issue on connect here but so far it was not confirmed as a CLR bug. But I would be surprised if my console application was to blame for a stack overflow in my test thread in a Monitor.Wait call. What is the moral of this story? Thread.Abort is evil but Thread.Interrupt is too. It is so evil that even the CLR of .NET 4.0 contains a race condition during the CLR shutdown. When the CLR gurus can get it wrong the chances are high that you get it wrong too when you use this constructs. If you do not believe me see what Patrick Smacchia does blog about Thread.Abort and List.Sort. Not only the CLR creators can get it wrong. The BCL writers do sometimes have a hard time with correct exception handling as well. If you do tell me that you use Thread.Abort frequently and never had problems with it I do suspect that you do not have looked deep enough into your application to find such sporadic errors.

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  • How should I design a wizard for generating requirements and documentation

    - by user1777663
    I'm currently working in an industry where extensive documentation is required, but the apps I'm writing are all pretty much cookie cutter at a high level. What I'd like to do is build an app that asks a series of questions regarding business rules and marketing requirements to generate a requirements spec. For example, there might be a question set that asks "Does the user need to enter their age?" and a follow-up question of "What is the minimum age requirement?" If the inputs are "yes" and "18", then this app will generate requirements that look something like this: "The registration form shall include an age selector" "The registration form shall throw an error if the selected age is less than 18" Later on down the line, I'd like to extend this to do additional things like generate test cases and even code, but the idea is the same: generate some output based on rules determined by answering a set of questions. Are there any patterns I could research to better design the architecture of such an application? Is this something that I should be modeling as a finite state machine?

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  • Twitter Tuesday - Top 10 @ArchBeat Tweets - May 27 - June 2, 2014

    - by OTN ArchBeat
    The Top 10 tweets from @OTNArchBeat for the last seven days, May 27- June 2, 2014.. RT @Java_EE: We changed the term from #J2EE and #JEE to Java EE in May 2006. Let's educate all users and especially recruiters. Retweet! May 30, 2014 at 12:00 AM Video: #kscope14 Preview: @timtow on Essbase Java API and @ODTUG Community Jun 02, 2014 at 12:00 AM #GoldenGate and #ODI - A Perfect Match in 12c - Part 1: Getting Started | Michael Rainey Jun 02, 2014 at 12:00 AM Podcast: Developing Enterprise Mobile Apps - Part 2 w/ @chriscmuir @fnimphiu @stevendavelaar @lucb_ May 29, 2014 at 12:00 AM Caveats on Using #WebLogic Server with JDK7 | @JayJayZheng May 28, 2014 at 12:00 AM SOA and Business Processes: You are the Process! @gschmutz @dschmied @t_winterberg et al #industrialsoa May 27, 2014 at 12:00 AM Video: #Kscope14 Preview: Data Modeling and Moving Meditation with @KentGraziano May 28, 2014 at 12:00 AM #Kscope14 Preview: @ericerikson on #HFM Metadata Diagnostics and more @ODTUG Jun 02, 2014 at 12:00 AM Extract Data from #FusionApps via Web Services | Richard Williams May 29, 2014 at 12:00 AM Top 10 @ArchBeat Tweets - May 20-26 #KScope14 #OBIEE #WebLogic #WebCenter May 27, 2014 at 12:00 AM

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  • Add Widget via Action in Toolbar

    - by Geertjan
    The question of the day comes from Vadim, who asks on the NetBeans Platform mailing list: "Looking for example showing how to add Widget to Scene, e.g. by toolbar button click." Well, the solution is very similar to this blog entry, where you see a solution provided by Jesse Glick for VisiTrend in Boston: https://blogs.oracle.com/geertjan/entry/zoom_capability Other relevant articles to read are as follows: http://netbeans.dzone.com/news/which-netbeans-platform-action http://netbeans.dzone.com/how-to-make-context-sensitive-actions Let's go through it step by step, with this result in the end, a solution involving 4 classes split (optionally, since a central feature of the NetBeans Platform is modularity) across multiple modules: The Customer object has a "name" String and the Droppable capability has a method "doDrop" which takes a Customer object: public interface Droppable {    void doDrop(Customer c);} In the TopComponent, we use "TopComponent.associateLookup" to publish an instance of "Droppable", which creates a new LabelWidget and adds it to the Scene in the TopComponent. Here's the TopComponent constructor: public CustomerCanvasTopComponent() {    initComponents();    setName(Bundle.CTL_CustomerCanvasTopComponent());    setToolTipText(Bundle.HINT_CustomerCanvasTopComponent());    final Scene scene = new Scene();    final LayerWidget layerWidget = new LayerWidget(scene);    Droppable d = new Droppable(){        @Override        public void doDrop(Customer c) {            LabelWidget customerWidget = new LabelWidget(scene, c.getTitle());            customerWidget.getActions().addAction(ActionFactory.createMoveAction());            layerWidget.addChild(customerWidget);            scene.validate();        }    };    scene.addChild(layerWidget);    jScrollPane1.setViewportView(scene.createView());    associateLookup(Lookups.singleton(d));} The Action is displayed in the toolbar and is enabled only if a Droppable is currently in the Lookup: @ActionID(        category = "Tools",        id = "org.customer.controler.AddCustomerAction")@ActionRegistration(        iconBase = "org/customer/controler/icon.png",        displayName = "#AddCustomerAction")@ActionReferences({    @ActionReference(path = "Toolbars/File", position = 300)})@NbBundle.Messages("AddCustomerAction=Add Customer")public final class AddCustomerAction implements ActionListener {    private final Droppable context;    public AddCustomerAction(Droppable droppable) {        this.context = droppable;    }    @Override    public void actionPerformed(ActionEvent ev) {        NotifyDescriptor.InputLine inputLine = new NotifyDescriptor.InputLine("Name:", "Data Entry");        Object result = DialogDisplayer.getDefault().notify(inputLine);        if (result == NotifyDescriptor.OK_OPTION) {            Customer customer = new Customer(inputLine.getInputText());            context.doDrop(customer);        }    }} Therefore, when the Properties window, for example, is selected, the Action will be disabled. (See the Zoomable example referred to in the link above for another example of this.) As you can see above, when the Action is invoked, a Droppable must be available (otherwise the Action would not have been enabled). The Droppable is obtained in the Action and a new Customer object is passed to its "doDrop" method. The above in pictures, take note of the enablement of the toolbar button with the red dot, on the extreme left of the toolbar in the screenshots below: The above shows the JButton is only enabled if the relevant TopComponent is active and, when the Action is invoked, the user can enter a name, after which a new LabelWidget is created in the Scene. The source code of the above is here: http://java.net/projects/nb-api-samples/sources/api-samples/show/versions/7.3/misc/WidgetCreationFromAction Note: Showing this as an MVC example is slightly misleading because, depending on which model object ("Customer" and "Droppable") you're looking at, the V and the C are different. From the point of view of "Customer", the TopComponent is the View, while the Action is the Controler, since it determines when the M is displayed. However, from the point of view of "Droppable", the TopComponent is the Controler, since it determines when the Action, i.e., which is in this case the View, displays the presence of the M.

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  • .NET Code Evolution

    - by Alois Kraus
    Originally posted on: http://geekswithblogs.net/akraus1/archive/2013/07/24/153504.aspxAt my day job I do look at a lot of code written by other people. Most of the code is quite good and some is even a masterpiece. And there is also code which makes you think WTF… oh it was written by me. Hm not so bad after all. There are many excuses reasons for bad code. Most often it is time pressure followed by not enough ambition (who cares) or insufficient training. Normally I do care about code quality quite a lot which makes me a (perceived) slow worker who does write many tests and refines the code quite a lot because of the design deficiencies. Most of the deficiencies I do find by putting my design under stress while checking for invariants. It does also help a lot to step into the code with a debugger (sometimes also Windbg). I do this much more often when my tests are red. That way I do get a much better understanding what my code really does and not what I think it should be doing. This time I do want to show you how code can evolve over the years with different .NET Framework versions. Once there was  time where .NET 1.1 was new and many C++ programmers did switch over to get rid of not initialized pointers and memory leaks. There were also nice new data structures available such as the Hashtable which is fast lookup table with O(1) time complexity. All was good and much code was written since then. At 2005 a new version of the .NET Framework did arrive which did bring many new things like generics and new data structures. The “old” fashioned way of Hashtable were coming to an end and everyone used the new Dictionary<xx,xx> type instead which was type safe and faster because the object to type conversion (aka boxing) was no longer necessary. I think 95% of all Hashtables and dictionaries use string as key. Often it is convenient to ignore casing to make it easy to look up values which the user did enter. An often followed route is to convert the string to upper case before putting it into the Hashtable. Hashtable Table = new Hashtable(); void Add(string key, string value) { Table.Add(key.ToUpper(), value); } This is valid and working code but it has problems. First we can pass to the Hashtable a custom IEqualityComparer to do the string matching case insensitive. Second we can switch over to the now also old Dictionary type to become a little faster and we can keep the the original keys (not upper cased) in the dictionary. Dictionary<string, string> DictTable = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase); void AddDict(string key, string value) { DictTable.Add(key, value); } Many people do not user the other ctors of Dictionary because they do shy away from the overhead of writing their own comparer. They do not know that .NET has for strings already predefined comparers at hand which you can directly use. Today in the many core area we do use threads all over the place. Sometimes things break in subtle ways but most of the time it is sufficient to place a lock around the offender. Threading has become so mainstream that it may sound weird that in the year 2000 some guy got a huge incentive for the idea to reduce the time to process calibration data from 12 hours to 6 hours by using two threads on a dual core machine. Threading does make it easy to become faster at the expense of correctness. Correct and scalable multithreading can be arbitrarily hard to achieve depending on the problem you are trying to solve. Lets suppose we want to process millions of items with two threads and count the processed items processed by all threads. A typical beginners code might look like this: int Counter; void IJustLearnedToUseThreads() { var t1 = new Thread(ThreadWorkMethod); t1.Start(); var t2 = new Thread(ThreadWorkMethod); t2.Start(); t1.Join(); t2.Join(); if (Counter != 2 * Increments) throw new Exception("Hmm " + Counter + " != " + 2 * Increments); } const int Increments = 10 * 1000 * 1000; void ThreadWorkMethod() { for (int i = 0; i < Increments; i++) { Counter++; } } It does throw an exception with the message e.g. “Hmm 10.222.287 != 20.000.000” and does never finish. The code does fail because the assumption that Counter++ is an atomic operation is wrong. The ++ operator is just a shortcut for Counter = Counter + 1 This does involve reading the counter from a memory location into the CPU, incrementing value on the CPU and writing the new value back to the memory location. When we do look at the generated assembly code we will see only inc dword ptr [ecx+10h] which is only one instruction. Yes it is one instruction but it is not atomic. All modern CPUs have several layers of caches (L1,L2,L3) which try to hide the fact how slow actual main memory accesses are. Since cache is just another word for redundant copy it can happen that one CPU does read a value from main memory into the cache, modifies it and write it back to the main memory. The problem is that at least the L1 cache is not shared between CPUs so it can happen that one CPU does make changes to values which did change in meantime in the main memory. From the exception you can see we did increment the value 20 million times but half of the changes were lost because we did overwrite the already changed value from the other thread. This is a very common case and people do learn to protect their  data with proper locking.   void Intermediate() { var time = Stopwatch.StartNew(); Action acc = ThreadWorkMethod_Intermediate; var ar1 = acc.BeginInvoke(null, null); var ar2 = acc.BeginInvoke(null, null); ar1.AsyncWaitHandle.WaitOne(); ar2.AsyncWaitHandle.WaitOne(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Intermediate did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Intermediate() { for (int i = 0; i < Increments; i++) { lock (this) { Counter++; } } } This is better and does use the .NET Threadpool to get rid of manual thread management. It does give the expected result but it can result in deadlocks because you do lock on this. This is in general a bad idea since it can lead to deadlocks when other threads use your class instance as lock object. It is therefore recommended to create a private object as lock object to ensure that nobody else can lock your lock object. When you read more about threading you will read about lock free algorithms. They are nice and can improve performance quite a lot but you need to pay close attention to the CLR memory model. It does make quite weak guarantees in general but it can still work because your CPU architecture does give you more invariants than the CLR memory model. For a simple counter there is an easy lock free alternative present with the Interlocked class in .NET. As a general rule you should not try to write lock free algos since most likely you will fail to get it right on all CPU architectures. void Experienced() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); t1.Wait(); t2.Wait(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Experienced did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Experienced() { for (int i = 0; i < Increments; i++) { Interlocked.Increment(ref Counter); } } Since time does move forward we do not use threads explicitly anymore but the much nicer Task abstraction which was introduced with .NET 4 at 2010. It is educational to look at the generated assembly code. The Interlocked.Increment method must be called which does wondrous things right? Lets see: lock inc dword ptr [eax] The first thing to note that there is no method call at all. Why? Because the JIT compiler does know very well about CPU intrinsic functions. Atomic operations which do lock the memory bus to prevent other processors to read stale values are such things. Second: This is the same increment call prefixed with a lock instruction. The only reason for the existence of the Interlocked class is that the JIT compiler can compile it to the matching CPU intrinsic functions which can not only increment by one but can also do an add, exchange and a combined compare and exchange operation. But be warned that the correct usage of its methods can be tricky. If you try to be clever and look a the generated IL code and try to reason about its efficiency you will fail. Only the generated machine code counts. Is this the best code we can write? Perhaps. It is nice and clean. But can we make it any faster? Lets see how good we are doing currently. Level Time in s IJustLearnedToUseThreads Flawed Code Intermediate 1,5 (lock) Experienced 0,3 (Interlocked.Increment) Master 0,1 (1,0 for int[2]) That lock free thing is really a nice thing. But if you read more about CPU cache, cache coherency, false sharing you can do even better. int[] Counters = new int[12]; // Cache line size is 64 bytes on my machine with an 8 way associative cache try for yourself e.g. 64 on more modern CPUs void Master() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Master, 0); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Master, Counters.Length - 1); t1.Wait(); t2.Wait(); Counter = Counters[0] + Counters[Counters.Length - 1]; if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Master did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Master(object number) { int index = (int) number; for (int i = 0; i < Increments; i++) { Counters[index]++; } } The key insight here is to use for each core its own value. But if you simply use simply an integer array of two items, one for each core and add the items at the end you will be much slower than the lock free version (factor 3). Each CPU core has its own cache line size which is something in the range of 16-256 bytes. When you do access a value from one location the CPU does not only fetch one value from main memory but a complete cache line (e.g. 16 bytes). This means that you do not pay for the next 15 bytes when you access them. This can lead to dramatic performance improvements and non obvious code which is faster although it does have many more memory reads than another algorithm. So what have we done here? We have started with correct code but it was lacking knowledge how to use the .NET Base Class Libraries optimally. Then we did try to get fancy and used threads for the first time and failed. Our next try was better but it still had non obvious issues (lock object exposed to the outside). Knowledge has increased further and we have found a lock free version of our counter which is a nice and clean way which is a perfectly valid solution. The last example is only here to show you how you can get most out of threading by paying close attention to your used data structures and CPU cache coherency. Although we are working in a virtual execution environment in a high level language with automatic memory management it does pay off to know the details down to the assembly level. Only if you continue to learn and to dig deeper you can come up with solutions no one else was even considering. I have studied particle physics which does help at the digging deeper part. Have you ever tried to solve Quantum Chromodynamics equations? Compared to that the rest must be easy ;-). Although I am no longer working in the Science field I take pride in discovering non obvious things. This can be a very hard to find bug or a new way to restructure data to make something 10 times faster. Now I need to get some sleep ….

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  • What is the best way to find a python google app engine coach?

    - by David Haddad
    i'm a software engineer and have been building Google App Engine apps with Python for about a year. I have a pretty good familiarity with the main concepts: web app framework, modeling, queues, memcache, django templates, etc. Where I think I'm lacking is in methodology. Architecting the app, using git for versioning, designing an writing unit tests. I'm totally convinced to incorporate these practices in my development style, and have started reading up on them. However I've learned that I'm a much faster learner when I have someone experienced to ask questions to and interact with. IRC channels and forums like stack overflow are great. But sometimes you want something more dynamic that produces results faster. So my question is how can a person find an experienced engineer that is familiar with the technologies he uses and that is willing to give them a couple of hours of Skype coaching sessions per week in return for an hourly fee...

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  • Oracle University Nuovi corsi (Week 10)

    - by swalker
    Oracle University ha recentemente rilasciato i seguenti nuovi corsi in inglese: Database RAC & Grid Infrastructure for Oracle Solaris System Administration (1 day) Oracle Database 11g: Performance Tuning (Training On Demand) Development Tools Oracle Database: Program with PL/SQL (Training On Demand) MySQL MySQL for Database Administrators (Training On Demand) Fusion Middleware Oracle WebCenter Portal 11g: Build Portals With Spaces (3 days) Oracle WebCenter Content 11g: Site Studio Essentials (5 days) Oracle BPM 11g Modeling (3 days) Business Intelligence & Datawarehousing Oracle BI Applications 7.9.6: Implementation for Oracle EBS (4 days) Oracle BI Applications 7.9.6: Implementation for Siebel CRM (4 days) Oracle BI 11g R1: Build Repositories (Training on Demand) Fusion Applications Fusion Applications: Extend Applications with ADF (5 days) E-Business Suite R12.x Extend Oracle Applications: Building OA Framework Applications (Training On Demand) PeopleSoft PeopleSoft Integration Tools Rel 8.50 (Training On Demand) Per ulteriori informazioni e per conoscere le date dei corsi, contattate il vostro Oracle University team locale.

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  • Documenting a REST interface with a flowchart

    - by James Kassemi
    Does anybody have suggestions on creating a flowchart representation of a REST-style web interface? In the interest of supplying thorough documentation to co-developers, I've been toying around in dia modeling the interface for modifying and generating a product resource: This particular system begins to act differently with user authentication/resource counts, so before I make modifications, I'm looking for some clarification: Complexity: how would you simplify the overall structure to make this easier to read? Display Symbol: is this appropriate for representing a page? Manual Operation Symbol: is this appropriate for representing a user action like a button click? Any other suggestions would be greatly appreciated. My apologies for the re-post. The main stackexchange site suggested this question was better presented on programmers.

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  • ASP.NET Multi-Select Radio Buttons

    - by Ajarn Mark Caldwell
    “HERESY!” you say, “Radio buttons are for single-select items!  If you want multi-select, use checkboxes!”  Well, I would agree, and that is why I consider this a significant bug that ASP.NET developers need to be aware of.  Here’s the situation. If you use ASP:RadioButton controls on your WebForm, then you know that in order to get them to behave properly, that is, to define a group in which only one of them can be selected by the user, you use the Group attribute and set the same value on each one.  For example: 1: <asp:RadioButton runat="server" ID="rdo1" Group="GroupName" checked="true" /> 2: <asp:RadioButton runat="server" ID="rdo2" Group="GroupName" /> With this configuration, the controls will render to the browser as HTML Input / Type=radio tags and when the user selects one, the browser will automatically deselect the other one so that only one can be selected (checked) at any time. BUT, if you user server-side code to manipulate the Checked attribute of these controls, it is possible to set them both to believe that they are checked. 1: rdo2.Checked = true; // Does NOT change the Checked attribute of rdo1 to be false. As long as you remain in server-side code, the system will believe that both radio buttons are checked (you can verify this in the debugger).  Therefore, if you later have code that looks like this 1: if (rdo1.Checked) 2: { 3: DoSomething1(); 4: } 5: else 6: { 7: DoSomethingElse(); 8: } then it will always evaluate the condition to be true and take the first action.  The good news is that if you return to the client with multiple radio buttons checked, the browser tries to clean that up for you and make only one of them really checked.  It turns out that the last one on the screen wins, so in this case, you will in fact end up with rdo2 as checked, and if you then make a trip to the server to run the code above, it will appear to be working properly.  However, if your page initializes with rdo2 checked and in code you set rdo1 to checked also, then when you go back to the client, rdo2 will remain checked, again because it is the last one and the last one checked “wins”. And this gets even uglier if you ever set these radio buttons to be disabled.  In that case, although the client browser renders the radio buttons as though only one of them is checked the system actually retains the value of both of them as checked, and your next trip to the server will really frustrate you because the browser showed rdo2 as checked, but your DoSomething1() routine keeps getting executed. The following is sample code you can put into any WebForm to test this yourself. 1: <body> 2: <form id="form1" runat="server"> 3: <h1>Radio Button Test</h1> 4: <hr /> 5: <asp:Button runat="server" ID="cmdBlankPostback" Text="Blank Postback" /> 6: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 7: <asp:Button runat="server" ID="cmdEnable" Text="Enable All" OnClick="cmdEnable_Click" /> 8: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 9: <asp:Button runat="server" ID="cmdDisable" Text="Disable All" OnClick="cmdDisable_Click" /> 10: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 11: <asp:Button runat="server" ID="cmdTest" Text="Test" OnClick="cmdTest_Click" /> 12: <br /><br /><br /> 13: <asp:RadioButton ID="rdoG1R1" GroupName="Group1" runat="server" Text="Group 1 Radio 1" Checked="true" /><br /> 14: <asp:RadioButton ID="rdoG1R2" GroupName="Group1" runat="server" Text="Group 1 Radio 2" /><br /> 15: <asp:RadioButton ID="rdoG1R3" GroupName="Group1" runat="server" Text="Group 1 Radio 3" /><br /> 16: <hr /> 17: <asp:RadioButton ID="rdoG2R1" GroupName="Group2" runat="server" Text="Group 2 Radio 1" /><br /> 18: <asp:RadioButton ID="rdoG2R2" GroupName="Group2" runat="server" Text="Group 2 Radio 2" Checked="true" /><br /> 19:  20: </form> 21: </body> 1: protected void Page_Load(object sender, EventArgs e) 2: { 3:  4: } 5:  6: protected void cmdEnable_Click(object sender, EventArgs e) 7: { 8: rdoG1R1.Enabled = true; 9: rdoG1R2.Enabled = true; 10: rdoG1R3.Enabled = true; 11: rdoG2R1.Enabled = true; 12: rdoG2R2.Enabled = true; 13: } 14:  15: protected void cmdDisable_Click(object sender, EventArgs e) 16: { 17: rdoG1R1.Enabled = false; 18: rdoG1R2.Enabled = false; 19: rdoG1R3.Enabled = false; 20: rdoG2R1.Enabled = false; 21: rdoG2R2.Enabled = false; 22: } 23:  24: protected void cmdTest_Click(object sender, EventArgs e) 25: { 26: rdoG1R2.Checked = true; 27: rdoG2R1.Checked = true; 28: } 29: 30: protected void Page_PreRender(object sender, EventArgs e) 31: { 32:  33: } After you copy the markup and page-behind code into the appropriate files.  I recommend you set a breakpoint on Page_Load as well as cmdTest_Click, and add each of the radio button controls to the Watch list so that you can walk through the code and see exactly what is happening.  Use the Blank Postback button to cause a postback to the server so you can inspect things without making any changes. The moral of the story is: if you do server-side manipulation of the Checked status of RadioButton controls, then you need to set ALL of the controls in a group whenever you want to change one.

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  • Which features of user story management should an agile team look for?

    - by Sonja Dimitrijevic
    In my research study, I need to identify the key features of user story management tools that can be used to support agile development. So far, I identified the following general groups of features: User role modeling and personas support, User stories and epics management, Acceptance testing support, High-level release planning, Low-level iteration planning, and Progress tracking. Each group contains some specific features, e.g., support for story points, writing of acceptance tests, etc. Which features of user story management should an agile team look for especially when switching from tangible tools (index cards, pin boards and big visible charts) to a software tool? Are some features more important than the others? Many thanks in advance!

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  • Web Services Example - Part 2: Programmatic

    - by Denis T
    In this edition of the ADF Mobile blog we'll tackle part 2 of our Web Service examples.  In this posting we'll take a look at using a SOAP Web Service but calling it programmatically in code and parsing the return into a bean. Getting the sample code: Just click here to download a zip of the entire project.  You can unzip it and load it into JDeveloper and deploy it either to iOS or Android.  Please follow the previous blog posts if you need help getting JDeveloper or ADF Mobile installed.  Note: This is a different workspace than WS-Part1 Defining our Web Service: Just like our first installment, we are using the same public weather forecast web service provided free by CDYNE Corporation.  Sometimes this service goes down so please ensure you know it's up before reporting this example isn't working. We're going to concentrate on the same two web service methods, GetCityForecastByZIP and GetWeatherInformation. Defing the Application: The application setup is identical to the Weather1 version.  There are some improvements to the data that is displayed as part of this example though.  Now we are able to show the associated image along with each forecast line when using the Forecast By Zip feature.  We've also added the temperature Hi/Low values into the UI. Summary of Fundamental Changes In This Application The most fundamental change is that we're binding the UI to the Bean Data Controls instead of directly to the Web Service Data Controls.  This gives us much more flexibility to control the shape of the data and allows us to do caching of the data outside of the Web Service.  This way if your application is, say offline, your bean could still populate with data from a local cache and still show you some UI as opposed to completely failing because you don't have any connectivity. In general we promote this type of programming technique with ADF Mobile to insulate your application from any issues with network connectivity. What's different with this example? We have setup the Web Service DC the same way but now we have managed beans to process the data.  The following classes define the "Model" of our application:  CityInformation-CityForecast-Forecast, WeatherInformation-WeatherDescription.  We use WeatherBean for UI interaction to the model layer.  If you look through this example, we don't really do that much with the java code except use it to grab the image URL from the weather description.  In a more realistic example, you might be using some JDBC classes to persist the data to a local database. To have a good architecture it is always good to keep your model and UI layers separate.  This gets muddied if you start to use bindings on a page invoked from Java code and this java code starts to become your "model" layer.  Since bindings are page specific, your model layer starts to become entwined with your UI.  Not good!  To help with this, we've added some utility functions that let you invoke DC methods without having a binding and thus execute methods from your "model" layer without requiring a binding in your page definition.  We do this with the invokeDataControlMethod of the AdfmfJavaUtilities class.  An example of this method call is available in line 95 of WeatherInformation.java and line 93 of CityInformation.Java. What's a GenericType? Because Web Service Data Controls (and also URL Data Controls AKA REST) use generic name/value pairs to define their structure and don't have strongly typed objects, these are actually stored internally as GenericType objects.  The GenericType class is simply a property map of name/value pairs that can be hierarchical.  There are methods like getAttribute where you supply the index of the attribute or it's string property name.  Why is this important to know?  Because invokeDataControlMethod returns GenericType objects and developers either need to parse these GenericType objects themselves or use one of our helper functions. GenericTypeBeanSerializationHelper This class does exactly what it's name implies.  It's a helper class for developers to aid in serialization of GenericTypes to/from java objects.  This is extremely handy if you have a large GenericType object with many attributes (or you're just lazy like me!) and you just want to parse it out into a real java object you can use more easily.  Here you would use the fromGenericType method.  This method takes the class of the Java object you wish to return and the GenericType as parameters.  The method then parses through each attribute in the GenericType and uses reflection to set that same attribute in the Java class.  Then the method returns that new object of the class you specified.  This is obviously very handy to avoid a lot of shuffling code between GenericType and your own Java classes.  The reverse method, toGenericType is also available when you want to go the other way.  In this case you supply the string that represents the package location in the DataControl definition (Example: "MyDC.myParams.MyCollection") and then pass in the Java object you have that holds the data and a GenericType is returned to you.  Again, it will use reflection to calculate the attributes that match between the java class and the GenericType and call the getters/setters on those. Issues and Possible Improvements: In the next installment we'll show you how to make your web service calls asynchronously so your UI will fill dynamically when the service call returns but in the meantime you show the data you have locally in your bean fed from some local cache.  This gives your users instant delivery of some data while you fetch other data in the background.

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