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  • C# vector class - Interpolation design decision

    - by Benjamin
    Currently I'm working on a vector class in C# and now I'm coming to the point, where I've to figure out, how i want to implement the functions for interpolation between two vectors. At first I came up with implementing the functions directly into the vector class... public class Vector3D { public static Vector3D LinearInterpolate(Vector3D vector1, Vector3D vector2, double factor) { ... } public Vector3D LinearInterpolate(Vector3D other, double factor { ... } } (I always offer both: a static method with two vectors as parameters and one non-static, with only one vector as parameter) ...but then I got the idea to use extension methods (defined in a seperate class called "Interpolation" for example), since interpolation isn't really a thing only available for vectors. So this could be another solution: public class Vector3D { ... } public static class Interpolation { public static Vector3D LinearInterpolate(this Vector3D vector, Vector3D other, double factor) { ... } } So here an example how you'd use the different possibilities: { var vec1 = new Vector3D(5, 3, 1); var vec2 = new Vector3D(4, 2, 0); Vector3D vec3; vec3 = vec1.LinearInterpolate(vec2, 0.5); //1 vec3 = Vector3D.LinearInterpolate(vec1, vec2, 0.5); //2 //or with extension-methods vec3 = vec1.LinearInterpolate(vec2, 0.5); //3 (same as 1) vec3 = Interpolation.LinearInterpolation(vec1, vec2, 0.5); //4 } So I really don't know which design is better. Also I don't know if there's an ultimate rule for things like this or if it's just about what someone personally prefers. But I really would like to hear your opinions, what's better (and if possible why ).

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  • Relative encapsulation design

    - by taher1992
    Let's say I am doing a 2D application with the following design: There is the Level object that manages the world, and there are world objects which are entities inside the Level object. A world object has a location and velocity, as well as size and a texture. However, a world object only exposes get properties. The set properties are private (or protected) and are only available to inherited classes. But of course, Level is responsible for these world objects, and must somehow be able to manipulate at least some of its private setters. But as of now, Level has no access, meaning world objects must change its private setters to public (violating encapsulation). How to tackle this problem? Should I just make everything public? Currently what I'm doing is having a inner class inside game object that does the set work. So when Level needs to update an objects location it goes something like this: void ChangeObject(GameObject targetObject, int newX, int newY){ // targetObject.SetX and targetObject.SetY cannot be set directly var setter = new GameObject.Setter(targetObject); setter.SetX(newX); setter.SetY(newY); } This code feels like overkill, but it doesn't feel right to have everything public so that anything can change an objects location for example.

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  • design for supporting entities with images

    - by brainydexter
    I have multiple entities like Hotels, Destination Cities etc which can contain images. The way I have my system setup right now is, I think of all the images belonging to this universal set (a table in the DB contains filePaths to all the images). When I have to add an image to an entity, I see if the entity exists in this universal set of images. If it exists, attach the reference to this image, else create a new image. E.g.: class ImageEntityHibernateDAO { public void addImageToEntity(IContainImage entity, String filePath, String title, String altText) { ImageEntity image = this.getImage(filePath); if (image == null) image = new ImageEntity(filePath, title, altText); getSession().beginTransaction(); entity.getImages().add(image); getSession().getTransaction().commit(); } } My question is: Earlier I had to write this code for each entity (and each entity would have a Set collection). So, instead of re-writing the same code, I created the following interface: public interface IContainImage { Set<ImageEntity> getImages(); } Entities which have image collections also implements IContainImage interface. Now, for any entity that needs to support adding Image functionality, all I have to invoke from the DAO looks something like this: // in DestinationDAO::addImageToDestination { imageDao.addImageToEntity(destination, imageFileName, imageTitle, imageAltText); // in HotelDAO::addImageToHotel { imageDao.addImageToEntity(hotel, imageFileName, imageTitle, imageAltText); It'd be great help if someone can provide me some critique on this design ? Are there any serious flaws that I'm not seeing right away ?

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  • Converting a Visual Studio 2003 Web Project to a Visual Studio 2008 Web Application Project

    - by navaneeth
    This walkthrough describes how to convert a Visual Studio .NET 2002 or Visual Studio .NET 2003 Web project to a Visual Studio 2008 Web application project. The Visual Studio 2008 Web application project model is like the Visual Studio 2005 Web application project model. Therefore, the conversion processes are similar. For more information about Web application projects, see ASP.NET Web Application Projects. You can also convert from a Visual Studio .NET Web project to a Visual Studio 2008 Web site project. However, conversion to a Web application project is the approach that is supported, and gives you the convenience of tools to help with the conversion. For example, when you convert to a Visual Studio 2008 Web application project, you can use the Visual Studio Conversion Wizard to automate part of the process. For information about how to convert a Visual Studio .NET Web project to a Visual Studio 2008 Web site, see Common Web Project Conversion Issues and Solutions. There are two parts involved in converting a Visual Studio 2002 or 2003 Web project to a Visual Studio 2008 Web application project. The parts are as follows: Converting the project. You can use the Visual Studio Conversion Wizard for the initial conversion of the project and Web.config files. You can later use the Convert To Web Application command to update the project's files and structure. Upgrading the .NET Framework version of the project. You must upgrade the project's .NET Framework version to either .NET Framework 2.0 SP1 or to .NET Framework 3.5. This .NET Framework version upgrade is required because Visual Studio 2008 cannot target earlier versions of the .NET Framework. You can perform this upgrade during the project conversion, by using the Conversion Wizard. Alternatively, you can upgrade the .NET Framework version after you convert the project.   NoteYou can change a project's .NET Framework version manually. To do so, in Visual Studio open the property pages for the project, click the Application tab, and then select a new version from the Target Framework list. This walkthrough illustrates the following tasks: Opening the Visual Studio .NET project in Visual Studio 2008 and creating a backup of the project files. Upgrading the .NET Framework version that the project targets. Converting the project file and the Web.config file. Converting ASP.NET code files. Testing the converted project. Prerequisites    To complete this walkthrough, you will need: Visual Studio 2008. A Web site project that was created in Visual Studio .NET version 2002 or 2003 that compiles and runs without errors. Converting the Project and Upgrading the .NET Framework Version    To begin, you open the project in Visual Studio 2008, which starts the conversion. It offers you an opportunity to back up the project before converting it. NoteIt is strongly recommended that you back up the project. The conversion works on the original project files, which cannot be recovered if the conversion is not successful.To convert the project and back up the files In Visual Studio 2008, in the File menu, click Open and then click Project. The Open Project dialog box is displayed. Browse to the folder that contains the project or solution file for the Visual Studio .NET project, select the file, and then click Open. NoteMake sure that you open the project by using the Open Project command. If you use the Open Web Site command, the project will be converted to the Web site project format.The Conversion Wizard opens and prompts you to create a backup before converting the project. To create the backup, click Yes. Click Browse, select the folder in which the backup should be created, and then click Next. Click Finish. The backup starts. NoteThere might be significant delays as the Conversion Wizard copies files, with no updates or progress indicated. Wait until the process finishes before you continue.When the conversion finishes, the wizard prompts you to upgrade the targeted version of the .NET Framework for the project. To upgrade to the .NET Framework 3.5, click Yes. To upgrade the project to target the .NET Framework 2.0 SP1, click No. It is recommended that you leave the check box selected that asks whether you want to upgrade all Webs in the solution. If you upgrade to .NET Framework 3.5, the project's Web.config file is modified at the same time as the project file. When the upgrade and conversion have finished, a message is displayed that indicates that you have completed the first step in converting your project. Click OK. The wizard displays status information about the conversion. Click Close. Testing the Converted Project    After the conversion has finished, you can test the project to make sure that it runs. This will also help you identify code in the project that must be updated. To verify that the project runs If you know about changes that are required for the code to run with the new version of the .NET Framework, make those changes. In the Build menu, click Build. Any missing references or other compilation issues in the project are displayed in the Error List window. The most likely issues are missing assembly references or issues with dynamically generated types. In Solution Explorer, right-click the Web page that will be used to launch the application, and then click Set as Start Page. On the Debug menu, click Start Debugging. If debugging is not enabled, the Debugging Not Enabled dialog box is displayed. Select the option to add a Web.config file that has debugging enabled, and then click OK. Verify that the converted project runs as expected. Do not continue with the conversion process until all build and run-time errors are resolved. Converting ASP.NET Code Files    ASP.NET Web page files and user-control files in Visual Studio 2008 that use the code-behind model have an associated designer file. The files that you just converted will have an associated code-behind file, but no designer file. Therefore, the next step is to generate designer files. NoteOnly ASP.NET Web pages and user controls that have their code in a separate code file require a separate designer file. For pages that have inline code and no associated code file, no designer file will be generated.To convert ASP.NET code files In Solution Explorer, right-click the project node, and then click Convert To Web Application. The files are converted. Verify that the converted code files have a code file and a designer file. Build and run the project to verify the results of the conversion.

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  • How to design a scalable notification system?

    - by Trent
    I need to write a notification system manager. Here is my requirements: I need to be able to send a Notification on different platforms, which may be totally different (for exemple, I need to be able to send either an SMS or an E-mail). Sometimes the notification may be the same for all recipients for a given platform, but sometimes it may be a notification per recipients (or several) per platform. Each notification can contain platform specific payload (for exemple an MMS can contains a sound or an image). The system need to be scalable, I need to be able to send a very large amount of notification without crashing either the application or the server. It is a two step process, first a customer may type a message and choose a platform to send to, and the notification(s) should be created to be processed either real-time either later. Then the system needs to send the notification to the platform provider. For now, I end up with some though but I don't know how scalable it will be or if it is a good design. I've though of the following objects (in a pseudo language): a generic Notification object: class Notification { String $message; Payload $payload; Collection<Recipient> $recipients; } The problem with the following objects is what if I've 1.000.000 recipients ? Even if the Recipient object is very small, it'll take too much memory. I could also create one Notification per recipient, but some platform providers requires me to send it in batch, meaning I need to define one Notification with several Recipients. Each created notification could be stored in a persistent storage like a DB or Redis. Would it be a good it to aggregate this later to make sure it is scalable? On the second step, I need to process this notification. But how could I distinguish the notification to the right platform provider? Should I use an object like MMSNotification extending an abstract Notification? or something like Notification.setType('MMS')? To allow to process a lot of notification at the same time, I think a messaging queue system like RabbitMQ may be the right tool. Is it? It would allow me to queue a lot of notification and have several worker to pop notification and process them. But what if I need to batch the recipients as seen above? Then I imagine a NotificationProcessor object for which I could I add NotificationHandler each NotificationHandler would be in charge to connect the platform provider and perform notification. I can also use an EventManager to allow pluggable behavior. Any feedbacks or ideas? Thanks for giving your time. Note: I'm used to work in PHP and it is likely the language of my choice.

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  • Purchasing Visual Studio 2010 Ultimate and Professional version

    - by Don
    We are a small team with 5-7 developers. We are planning to purchase Visual Studio 2010, better with one or two Ultimate version, others with professional version. The suggestion from Microsoft is getting it from retail. We find we can get them from http://msdn.microsoft.com/en-us/subscriptions/buy.aspx or http://www.amazon.com/Visual-Studio-2010-Ultimate-MSDN/dp/B0038KNER0/ref=sr_1_fkmr3_2?ie=UTF8&qid=1296675635&sr=8-2-fkmr3. From Amazon, it will be lower cost. We wonder if we buy from Microsft directly we can get additional benefits like supports, which other retailers can not provide. Anyone has any ideas? What is the cost effient way? Thanks,

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  • Best Design Pattern for Coupling User Interface Components and Data Structures

    - by szahn
    I have a windows desktop application with a tree view. Due to lack of a sound data-binding solution for a tree view, I've implemented my own layer of abstraction on it to bind nodes to my own data structure. The requirements are as follows: Populate a tree view with nodes that resemble fields in a data structure. When a node is clicked, display the appropriate control to modify the value of that property in the instance of the data structure. The tree view is populated with instances of custom TreeNode classes that inherit from TreeNode. The responsibility of each custom TreeNode class is to (1) format the node text to represent the name and value of the associated field in my data structure, (2) return the control used to modify the property value, (3) get the value of the field in the control (3) set the field's value from the control. My custom TreeNode implementation has a property called "Control" which retrieves the proper custom control in the form of the base control. The control instance is stored in the custom node and instantiated upon first retrieval. So each, custom node has an associated custom control which extends a base abstract control class. Example TreeNode implementation: //The Tree Node Base Class public abstract class TreeViewNodeBase : TreeNode { public abstract CustomControlBase Control { get; } public TreeViewNodeBase(ExtractionField field) { UpdateControl(field); } public virtual void UpdateControl(ExtractionField field) { Control.UpdateControl(field); UpdateCaption(FormatValueForCaption()); } public virtual void SaveChanges(ExtractionField field) { Control.SaveChanges(field); UpdateCaption(FormatValueForCaption()); } public virtual string FormatValueForCaption() { return Control.FormatValueForCaption(); } public virtual void UpdateCaption(string newValue) { this.Text = Caption; this.LongText = newValue; } } //The tree node implementation class public class ExtractionTypeNode : TreeViewNodeBase { private CustomDropDownControl control; public override CustomControlBase Control { get { if (control == null) { control = new CustomDropDownControl(); control.label1.Text = Caption; control.comboBox1.Items.Clear(); control.comboBox1.Items.AddRange( Enum.GetNames( typeof(ExtractionField.ExtractionType))); } return control; } } public ExtractionTypeNode(ExtractionField field) : base(field) { } } //The custom control base class public abstract class CustomControlBase : UserControl { public abstract void UpdateControl(ExtractionField field); public abstract void SaveChanges(ExtractionField field); public abstract string FormatValueForCaption(); } //The custom control generic implementation (view) public partial class CustomDropDownControl : CustomControlBase { public CustomDropDownControl() { InitializeComponent(); } public override void UpdateControl(ExtractionField field) { //Nothing to do here } public override void SaveChanges(ExtractionField field) { //Nothing to do here } public override string FormatValueForCaption() { //Nothing to do here return string.Empty; } } //The custom control specific implementation public class FieldExtractionTypeControl : CustomDropDownControl { public override void UpdateControl(ExtractionField field) { comboBox1.SelectedIndex = comboBox1.FindStringExact(field.Extraction.ToString()); } public override void SaveChanges(ExtractionField field) { field.Extraction = (ExtractionField.ExtractionType) Enum.Parse(typeof(ExtractionField.ExtractionType), comboBox1.SelectedItem.ToString()); } public override string FormatValueForCaption() { return string.Empty; } The problem is that I have "generic" controls which inherit from CustomControlBase. These are just "views" with no logic. Then I have specific controls that inherit from the generic controls. I don't have any functions or business logic in the generic controls because the specific controls should govern how data is associated with the data structure. What is the best design pattern for this?

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  • Visual Studio Extensions

    - by Scott Dorman
    Originally posted on: http://geekswithblogs.net/sdorman/archive/2013/10/18/visual-studio-extensions.aspxAs a product, Visual Studio has been around for a long time. In fact, it’s been 18 years since the first Visual Studio product was launched. In that time, there have been some major changes but perhaps the most important (or at least influential) changes for the course of the product have been in the last few years. While we can argue over what was and wasn’t an important change or what has and hasn’t changed, I want to talk about what I think is the single most important change Microsoft has made to Visual Studio. Specifically, I’m referring to the Visual Studio Gallery (first introduced in Visual Studio 2010) and the ability for third-parties to easily write extensions which can add new functionality to Visual Studio or even change existing functionality. I know Visual Studio had this ability before the Gallery existed, but it was expensive (both from a financial and development resource) perspective for a company or individual to write such an extension. The Visual Studio Gallery changed all of that. As of today, there are over 4000 items in the Gallery. Microsoft itself has over 100 items in the Gallery and more are added all of the time. Why is this such an important feature? Simply put, it allows third-parties (companies such as JetBrains, Telerik, Red Gate, Devart, and DevExpress, just to name a few) to provide enhanced developer productivity experiences directly within the product by providing new functionality or changing existing functionality. However, there is an even more important function that it serves. It also allows Microsoft to do the same. By providing extensions which add new functionality or change existing functionality, Microsoft is not only able to rapidly innovate on new features and changes but to also get those changes into the hands of developers world-wide for feedback. The end result is that these extensions become very robust and often end up becoming part of a later product release. An excellent example of this is the new CodeLens feature of Visual Studio 2013. This is, perhaps, the single most important developer productivity enhancement released in the last decade and already has huge potential. As you can see, out of the box CodeLens supports showing you information about references, unit tests and TFS history.   Fortunately, CodeLens is also accessible to Visual Studio extensions, and Microsoft DevLabs has already written such an extension to show code “health.” This extension shows different code metrics to help make sure your code is maintainable. At this point, you may have already asked yourself, “With over 4000 extensions, how do I find ones that are good?” That’s a really good question. Fortunately, the Visual Studio Gallery has a ratings system in place, which definitely helps but that’s still a lot of extensions to look through. To that end, here is my personal list of favorite extensions. This is something I started back when Visual Studio 2010 was first released, but so much has changed since then that I thought it would be good to provide an updated list for Visual Studio 2013. These are extensions that I have installed and use on a regular basis as a developer that I find indispensible. This list is in no particular order. NuGet Package Manager for Visual Studio 2013 Microsoft CodeLens Code Health Indicator Visual Studio Spell Checker Indent Guides Web Essentials 2013 VSCommands for Visual Studio 2013 Productivity Power Tools (right now this is only for Visual Studio 2012, but it should be updated to support Visual Studio 2013.) Everyone has their own set of favorites, so mine is probably not going to match yours. If there is an extension that you really like, feel free to leave me a comment!

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  • Replacing/Extending Visual Studio's Generate Stub in Visual Studio 2010

    - by devoured elysium
    When we write the name of a method that doesn't exist, Visual Studio 2010 asks us if we'd like to generate a method stub with that name. What I'd like to know if is it possible to replace that same code stub generating command with one made by myself. I never did any kind of extensibility programming for Visual Studio so I have a couple of questions: How hard is it? Is it something I can learn in a couple of nights, or is it something that'll make me "lose" a lot of time? It seems to me that there isn't a lot of support for that kind of programming, as generally people are not that interested in developing solutions that extend the Visual Studio IDE. I searched on SO and it doesn't appear to have many threads about extending Visual Studio. I don't know how the generate method stub thing works in Visual Studio, but I just wanted to turn it into something a bit more flexible and useful. Has anyone dealt with these kind of things before, that can give me a pointer to where to start? I know of MS VSX site but that has a lot of resources and can be overwhelming for someone new to the subject as I am. What technology will I need to use? T4? Maybe I'll need to know a lot about the code, like Visual Studio does, so I can know other method's type arguments, names, etc. Is that what T4 is for? Thanks

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  • New HTML 5 input types in ASP.Net 4.5 Developer Preview

    - by sreejukg
    Microsoft has released developer previews for Visual Studio 2011 and .Net framework 4.5. There are lots of new features available in the developer preview. One of the most interested things for web developers is the support introduced for new HTML 5 form controls. The following are the list of new controls available in HTML 5 email url number range Date pickers (date, month, week, time, datetime, datetime-local) search color Describing the functionality for these controls is not in the scope of this article. If you want to know about these controls, refer the below URLs http://msdn.microsoft.com/en-us/magazine/hh547102.aspx http://www.w3schools.com/html5/html5_form_input_types.asp ASP.Net 4.5 introduced more possible values to the Text Mode attribute to cater the above requirements. Let us evaluate these. I have created a project in Visual Studio 2011 developer preview, and created a page named “controls.aspx”. In the page I placed on Text box control from the toolbox Now select the control and go to the properties pane, look at the TextMode attribute. Now you can see more options are added here than prior versions of ASP.Net. I just selected Email as TextMode. I added one button to submit my page. The screen shot of the page in Visual Studio 2011 designer is as follows See the corresponding markup <form id="form1" runat="server">     <div>         Enter your email:         <asp:TextBox ID="TextBox1" runat="server" TextMode="Email"></asp:TextBox     </div>     <asp:Button ID="Button1" runat="server" Text="Submit" /> </form> Now let me run this page, IE 9 do not have the support for new form fields. I browsed the page using Firefox and the page appears as below. From the source of the rendered page, I saw the below markup for my email textbox <input name="TextBox1" type="email" id="TextBox1" /> Try to enter an invalid email and you will see the browser will ask you to enter a valid one by default. When rendered in non-supported browsers, these fields are behaving just as normal text boxes. So make sure you are using validation controls with these fields. See the browser support compatability matrix with these controls with various browser vendors. ASP.Net 4.5 introduced the support for these new form controls. You can build interactive forms using the newly added controls, keeping in mind that you need to validate the data for non-supported browsers.

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  • Membership in ASP.Net applications - part 2

    - by nikolaosk
    This is the second post in a series of posts regarding ASP.Net built in membership functionality,providers,controls. You can read the first one post one here . In order to follow this post, complete the steps in the first post. It will only take 10 minutes or so. 1) Launch Visual Studio 2005,2008/2010. Express editions will work fine. I am using Visual Studio 2010 Ultimate edition. 2) Follow all the steps in the first post of the series. 3) Run your application to make sure it runs. 4) Change the...(read more)

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  • Microsoft Visual Studio Team Explorer 2010 codename “Eaglestone”

    - by HosamKamel
    Microsoft has released the beta release of Microsoft Visual Studio Team Explorer 2010 codename “Eaglestone”, the Eclipse plugin and cross-platform command line assets that were acquired from Teamprise back in November. You can download the bits here, and participate in the associated Microsoft Connect community here. Changes done in this release : All of the architectural changes in TFS 2010 has been reacted, which primarily shows up in our support for Team Project Collections but it also means that the Eclipse plug-in supports all the configurations for project portal and reporting services that are possible (including not having any configured at all) Added the enhanced work item linking and hierarchy capabilities.  You can now define typed links, query for work items based on links, and work with work item hierarchies. Added support for the new WF-based team build Have reacted to a lot of underlying changes in the source control version model with respect to how branching, merging, and renames happen. History now follows branches and merges. Branches are proper first class citizens in the source control explorer. You can check a detailed post written  by bharry here Microsoft Visual Studio Team Explorer 2010 codename “Eaglestone”

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  • Test Driven Development (TDD) in Visual Studio 2010- Microsoft Mondays

    - by Hosam Kamel
    November 14th , I will be presenting at Microsoft Mondays a session about Test Driven Development (TDD) in Visual Studio 2010 . Microsoft Mondays is program consisting of a series of Webcasts showcasing various Microsoft products and technologies. Each Monday we discuss a particular topic pertaining to development, infrastructure, Office tools, ERP, client/server operating systems etc. The webcast will be broadcast via Lync and can viewed from a web client. The idea behind the “Microsoft Mondays” program is to help you become more proficient in the products and technologies that you use and help you utilize their full potential.   Test Driven Development in Visual Studio 2010 Level – 300 (  Intermediate – Advanced ) Test Driven Development (TDD), also frequently referred to as Test Driven Design, is a development methodology where developers create software by first writing a unit test, then writing the actual system code to make the unit test pass.  The unit test can be viewed as a small specification around how the system should behave; writing it first helps the developer to focus on only writing enough code to make the test pass, thereby helping ensure a tight, lightweight system which is specifically focused meeting on the documented requirements. TDD follows a cadence of “Red, Green, Refactor.” Red refers to the visual display of a failing test – the test you write first will not pass because you have not yet written any code for it. Green refers to the step of writing just enough code in your system to make your unit test pass – your test runner’s UI will now show that test passing with a green icon. Refactor refers to the step of refactoring your code so it is tighter, cleaner, and more flexible. This cycle is repeated constantly throughout a TDD developer’s workday. Date:   November 14, 2011 Time:  10:00 a.m. – 11:00 a.m. (GMT+3)  http://www.eventbrite.com/event/2437620990/efbnen?ebtv=F   See you there! Hosam Kamel Originally posted at

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  • Design for a plugin based application

    - by Varun Naik
    I am working on application, details of which I cannot discuss here. We have core framework and the rest is designed as plug in. In the core framework we have a domain object. This domain object is updated by the plugins. I have defined an interface in which I have function as DomainObject doProcessing(DomainObject object) My intention here is I pass the domain object, the plug in will update it and return it. This updated object is then passed again to different plugin to be updated. I am not sure if this is a good approach. I don't like passing the DomainObject to plugin. Is there a better way I can achieve this? Should I just request data from plugin and update the domain object myself?

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  • Class Design and Structure Online Web Store

    - by Phorce
    I hope I have asked this in the right forum. Basically, we're designing an Online Store and I am designing the class structure for ordering a product and want some clarification on what I have so far: So a customer comes, selects their product, chooses the quantity and selects 'Purchase' (I am using the Facade Pattern - So subsystems execute when this action is performed). My class structure: < Order > < Product > <Customer > There is no inheritance, more Association < Order has < Product , < Customer has < Order . Does this structure look ok? I've noticed that I don't handle the "Quantity" separately, I was just going to add this into the "Product" class, but, do you think it should be a class of it's own? Hope someone can help.

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  • Caching factory design

    - by max
    I have a factory class XFactory that creates objects of class X. Instances of X are very large, so the main purpose of the factory is to cache them, as transparently to the client code as possible. Objects of class X are immutable, so the following code seems reasonable: # module xfactory.py import x class XFactory: _registry = {} def get_x(self, arg1, arg2, use_cache = True): if use_cache: hash_id = hash((arg1, arg2)) if hash_id in _registry: return _registry[hash_id] obj = x.X(arg1, arg2) _registry[hash_id] = obj return obj # module x.py class X: # ... Is it a good pattern? (I know it's not the actual Factory Pattern.) Is there anything I should change? Now, I find that sometimes I want to cache X objects to disk. I'll use pickle for that purpose, and store as values in the _registry the filenames of the pickled objects instead of references to the objects. Of course, _registry itself would have to be stored persistently (perhaps in a pickle file of its own, in a text file, in a database, or simply by giving pickle files the filenames that contain hash_id). Except now the validity of the cached object depends not only on the parameters passed to get_x(), but also on the version of the code that created these objects. Strictly speaking, even a memory-cached object could become invalid if someone modifies x.py or any of its dependencies, and reloads it while the program is running. So far I ignored this danger since it seems unlikely for my application. But I certainly cannot ignore it when my objects are cached to persistent storage. What can I do? I suppose I could make the hash_id more robust by calculating hash of a tuple that contains arguments arg1 and arg2, as well as the filename and last modified date for x.py and every module and data file that it (recursively) depends on. To help delete cache files that won't ever be useful again, I'd add to the _registry the unhashed representation of the modified dates for each record. But even this solution isn't 100% safe since theoretically someone might load a module dynamically, and I wouldn't know about it from statically analyzing the source code. If I go all out and assume every file in the project is a dependency, the mechanism will still break if some module grabs data from an external website, etc.). In addition, the frequency of changes in x.py and its dependencies is quite high, leading to heavy cache invalidation. Thus, I figured I might as well give up some safety, and only invalidate the cache only when there is an obvious mismatch. This means that class X would have a class-level cache validation identifier that should be changed whenever the developer believes a change happened that should invalidate the cache. (With multiple developers, a separate invalidation identifier is required for each.) This identifier is hashed along with arg1 and arg2 and becomes part of the hash keys stored in _registry. Since developers may forget to update the validation identifier or not realize that they invalidated existing cache, it would seem better to add another validation mechanism: class X can have a method that returns all the known "traits" of X. For instance, if X is a table, I might add the names of all the columns. The hash calculation will include the traits as well. I can write this code, but I am afraid that I'm missing something important; and I'm also wondering if perhaps there's a framework or package that can do all of this stuff already. Ideally, I'd like to combine in-memory and disk-based caching.

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  • design a model for a system of dependent variables

    - by dbaseman
    I'm dealing with a modeling system (financial) that has dozens of variables. Some of the variables are independent, and function as inputs to the system; most of them are calculated from other variables (independent and calculated) in the system. What I'm looking for is a clean, elegant way to: define the function of each dependent variable in the system trigger a re-calculation, whenever a variable changes, of the variables that depend on it A naive way to do this would be to write a single class that implements INotifyPropertyChanged, and uses a massive case statement that lists out all the variable names x1, x2, ... xn on which others depend, and, whenever a variable xi changes, triggers a recalculation of each of that variable's dependencies. I feel that this naive approach is flawed, and that there must be a cleaner way. I started down the path of defining a CalculationManager<TModel> class, which would be used (in a simple example) something like as follows: public class Model : INotifyPropertyChanged { private CalculationManager<Model> _calculationManager = new CalculationManager<Model>(); // each setter triggers a "PropertyChanged" event public double? Height { get; set; } public double? Weight { get; set; } public double? BMI { get; set; } public Model() { _calculationManager.DefineDependency<double?>( forProperty: model => model.BMI, usingCalculation: (height, weight) => weight / Math.Pow(height, 2), withInputs: model => model.Height, model.Weight); } // INotifyPropertyChanged implementation here } I won't reproduce CalculationManager<TModel> here, but the basic idea is that it sets up a dependency map, listens for PropertyChanged events, and updates dependent properties as needed. I still feel that I'm missing something major here, and that this isn't the right approach: the (mis)use of INotifyPropertyChanged seems to me like a code smell the withInputs parameter is defined as params Expression<Func<TModel, T>>[] args, which means that the argument list of usingCalculation is not checked at compile time the argument list (weight, height) is redundantly defined in both usingCalculation and withInputs I am sure that this kind of system of dependent variables must be common in computational mathematics, physics, finance, and other fields. Does someone know of an established set of ideas that deal with what I'm grasping at here? Would this be a suitable application for a functional language like F#? Edit More context: The model currently exists in an Excel spreadsheet, and is being migrated to a C# application. It is run on-demand, and the variables can be modified by the user from the application's UI. Its purpose is to retrieve variables that the business is interested in, given current inputs from the markets, and model parameters set by the business.

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  • Design for object with optional and modifiable attributtes?

    - by Ikuzen
    I've been using the Builder pattern to create objects with a large number of attributes, where most of them are optional. But up until now, I've defined them as final, as recommended by Joshua Block and other authors, and haven't needed to change their values. I am wondering what should I do though if I need a class with a substantial number of optional but non-final (mutable) attributes? My Builder pattern code looks like this: public class Example { //All possible parameters (optional or not) private final int param1; private final int param2; //Builder class public static class Builder { private final int param1; //Required parameters private int param2 = 0; //Optional parameters - initialized to default //Builder constructor public Builder (int param1) { this.param1 = param1; } //Setter-like methods for optional parameters public Builder param2(int value) { param2 = value; return this; } //build() method public Example build() { return new Example(this); } } //Private constructor private Example(Builder builder) { param1 = builder.param1; param2 = builder.param2; } } Can I just remove the final keyword from the declaration to be able to access the attributes externally (through normal setters, for example)? Or is there a creational pattern that allows optional but non-final attributes that would be better suited in this case?

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  • Learning how to design knowledge and data flow [closed]

    - by max
    In designing software, I spend a lot of time deciding how the knowledge (algorithms / business logic) and data should be allocated between different entities; that is, which object should know what. I am asking for advice about books, articles, presentations, classes, or other resources that would help me learn how to do it better. I code primarily in Python, but my question is not really language-specific; even if some of the insights I learn don't work in Python, that's fine. I'll give a couple examples to clarify what I mean. Example 1 I want to perform some computation. As a user, I will need to provide parameters to do the computation. I can have all those parameters sent to the "main" object, which then uses them to create other objects as needed. Or I can create one "main" object, as well as several additional objects; the additional objects would then be sent to the "main" object as parameters. What factors should I consider to make this choice? Example 2 Let's say I have a few objects of type A that can perform a certain computation. The main computation often involves using an object of type B that performs some interim computation. I can either "teach" A instances what exact parameters to pass to B instances (i.e., make B "dumb"); or I can "teach" B instances to figure out what needs to be done when looking at an A instance (i.e., make B "smart"). What should I think about when I'm making this choice?

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  • High-Level Application Architecture Question

    - by Jesse Bunch
    So I'm really wanting to improve how I architect the software I code. I want to focus on maintainability and clean code. As you might guess, I've been reading a lot of resources on this topic and all it's doing is making it harder for me to settle on an architecture because I can never tell if my design is the one that the more experienced programmer would've chosen. So I have these requirements: I should connect to one vendor and download form submissions from their API. We'll call them the CompanyA. I should then map those submissions to a schema fit for submitting to another vendor for integration with the email service provider. We'll call them the CompanyB. I should then submit those responses to the ESP (CompanyB) and then instruct the ESP to send that submitter an email. So basically, I'm copying data from one web service to another and then performing an action at the latter web service. I've identified a couple high-level services: The service that downloads data from CompanyA. I called this the CompanyAIntegrator. The service that submits the data to CompanyB. I called this CompanyBIntegrator. So my questions are these: Is this a good design? I've tried to separate the concerns and am planning to use the facade pattern to make the integrators interchangeable if the vendors change in the future. Are my naming conventions accurate and meaningful to you (who knows nothing specific of the project)? Now that I have these services, where should I do the work of taking output from the CompanyAIntegrator and getting it in the format for input to the CompanyBIntegrator? Is this OK to be done in main()? Do you have any general pointers on how you'd code something like this? I imagine this scenario is common to us engineers---especially those working in agencies. Thanks for any help you can give. Learning how to architect well is really mind-cluttering.

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  • How bad is it to have two methods with the same name but different signatures in two classes?

    - by Super User
    I have a design problem related to a public interface, the names of methods, and the understanding of my API and code. I have two classes like this: class A: ... function collision(self): .... ... class B: .... function _collision(self, another_object, l, r, t, b): .... The first class has one public method named collision, and the second has one private method called _collision. The two methods differs in argument type and number. As an example let's say that _collision checks if the object is colliding with another object with certain conditions l, r, t, b (collide on the left side, right side, etc) and returns true or false. The public collision method, on the other hand, resolves all the collisions of the object with other objects. The two methods have the same name because I think it's better to avoid overloading the design with different names for methods that do almost the same thing, but in distinct contexts and classes. Is this clear enough to the reader or I should change the method's name?

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  • How bad it's have two methods with the same name but differents signatures in two classes?

    - by Super User
    I have a design problem relationated with the public interface, the names of methods and the understanding of my API and my code. I have two classes like this: class A: ... function collision(self): .... ... class B: .... function _collision(self, another_object, l, r, t, b): .... The first class have one public method named collision and the second have one private method called _collision. The two methods differs in arguments type and number. In the API _m method is private. For the example let's say that the _collision method checks if the object is colliding with another_ object with certain conditions l, r, t, b (for example, collide the left side, the right side, etc) and returns true or false according to the case. The collision method, on the other hand, resolves all the collisions of the object with other objects. The two methods have the same name because I think is better avoid overload the design with different names for methods who do almost the same think, but in distinct contexts and classes. This is clear enough to the reader or I should change the method's name?

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  • Clean up after Visual Studio

    - by psheriff
    As programmer’s we know that if we create a temporary file during the running of our application we need to make sure it is removed when the application or process is complete. We do this, but why can’t Microsoft do it? Visual Studio leaves tons of temporary files all over your hard drive. This is why, over time, your computer loses hard disk space. This blog post will show you some of the most common places where these files are left and which ones you can safely delete..NET Left OversVisual Studio is a great development environment for creating applications quickly. However, it will leave a lot of miscellaneous files all over your hard drive. There are a few locations on your hard drive that you should be checking to see if there are left-over folders or files that you can delete. I have attempted to gather as much data as I can about the various versions of .NET and operating systems. Of course, your mileage may vary on the folders and files I list here. In fact, this problem is so prevalent that PDSA has created a Computer Cleaner specifically for the Visual Studio developer.  Instructions for downloading our PDSA Developer Utilities (of which Computer Cleaner is one) are at the end of this blog entry.Each version of Visual Studio will create “temporary” files in different folders. The problem is that the files created are not always “temporary”. Most of the time these files do not get cleaned up like they should. Let’s look at some of the folders that you should periodically review and delete files within these folders.Temporary ASP.NET FilesAs you create and run ASP.NET applications from Visual Studio temporary files are placed into the <sysdrive>:\Windows\Microsoft.NET\Framework[64]\<vernum>\Temporary ASP.NET Files folder. The folders and files under this folder can be removed with no harm to your development computer. Do not remove the "Temporary ASP.NET Files" folder itself, just the folders underneath this folder. If you use IIS for ASP.NET development, you may need to run the iisreset.exe utility from the command prompt prior to deleting any files/folder under this folder. IIS will sometimes keep files in use in this folder and iisreset will release the locks so the files/folders can be deleted.Website CacheThis folder is similar to the ASP.NET Temporary Files folder in that it contains files from ASP.NET applications run from Visual Studio. This folder is located in each users local settings folder. The location will be a little different on each operating system. For example on Windows Vista/Windows 7, the folder is located at <sysdrive>:\Users\<UserName>\AppData\Local\Microsoft\WebsiteCache. If you are running Windows XP this folder is located at <sysdrive>:\ Documents and Settings\<UserName>\Local Settings\Application Data\Microsoft\WebsiteCache. Check these locations periodically and delete all files and folders under this directory.Visual Studio BackupThis backup folder is used by Visual Studio to store temporary files while you develop in Visual Studio. This folder never gets cleaned out, so you should periodically delete all files and folders under this directory. On Windows XP, this folder is located at <sysdrive>:\Documents and Settings\<UserName>\My Documents\Visual Studio 200[5|8]\Backup Files. On Windows Vista/Windows 7 this folder is located at <sysdrive>:\Users\<UserName>\Documents\Visual Studio 200[5|8]\.Assembly CacheNo, this is not the global assembly cache (GAC). It appears that this cache is only created when doing WPF or Silverlight development with Visual Studio 2008 or Visual Studio 2010. This folder is located in <sysdrive>:\ Users\<UserName>\AppData\Local\assembly\dl3 on Windows Vista/Windows 7. On Windows XP this folder is located at <sysdrive>:\ Documents and Settings\<UserName>\Local Settings\Application Data\assembly. If you have not done any WPF or Silverlight development, you may not find this particular folder on your machine.Project AssembliesThis is yet another folder where Visual Studio stores temporary files. You will find a folder for each project you have opened and worked on. This folder is located at <sysdrive>:\Documents and Settings\<UserName>Local Settings\Application Data\Microsoft\Visual Studio\[8|9].0\ProjectAssemblies on Windows XP. On Microsoft Vista/Windows 7 you will find this folder at <sysdrive>:\Users\<UserName>\AppData\Local\Microsoft\Visual Studio\[8|9].0\ProjectAssemblies.Remember not all of these folders will appear on your particular machine. Which ones do show up will depend on what version of Visual Studio you are using, whether or not you are doing desktop or web development, and the operating system you are using.SummaryTaking the time to periodically clean up after Visual Studio will aid in keeping your computer running quickly and increase the space on your hard drive. Another place to make sure you are cleaning up is your TEMP folder. Check your OS settings for the location of your particular TEMP folder and be sure to delete any files in here that are not in use. I routinely clean up the files and folders described in this blog post and I find that I actually eliminate errors in Visual Studio and I increase my hard disk space.NEW! PDSA has just published a “pre-release” of our PDSA Developer Utilities at http://www.pdsa.com/DeveloperUtilities that contains a Computer Cleaner utility which will clean up the above-mentioned folders, as well as a lot of other miscellaneous folders that get Visual Studio build-up. You can download a free trial at http://www.pdsa.com/DeveloperUtilities. If you wish to purchase our utilities through the month of November, 2011 you can use the RSVP code: DUNOV11 to get them for only $39. This is $40 off the regular price.NOTE: You can download this article and many samples like the one shown in this blog entry at my website. http://www.pdsa.com/downloads. Select “Tips and Tricks”, then “Developer Machine Clean Up” from the drop down list.Good Luck with your Coding,Paul Sheriff** SPECIAL OFFER FOR MY BLOG READERS **We frequently offer a FREE gift for readers of my blog. Visit http://www.pdsa.com/Event/Blog for your FREE gift!

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  • Templates for forms, tabs etc? - Patterntap alternatives

    - by Marco Demaio
    I used to find http://www.patterntap.com quite useful to get design inspiration for forms, tabs, and other web elements etc. Unfortunately after the ZURB acquisition of Patterntap now they enforce you to sign in with your Twitter account in order to simply view larger images of patterns provided by the crowd. So in some way it's not free anymore. Do you know of alternatives to patterntap that are free and you are not obliged to sign in?

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