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• Business layer access to the data layer

  - by rerun

  I have a Business layer (BL) and a Data layer (DL). I have an object o with a child objects collection of Type C. I would like to provide a semantics like the following o.Children.Add("info"). In the BL I would like to have a static CLASS that all of business layer classes uses to get a reference to the current datalayer instance. Is there any issue with that or must I use the factory pattern to limit creation to A class in the BL that knows the DL instance.

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• Lambda&rsquo;s for .NET made easy&hellip;

  - by mbcrump

  The purpose of my blog is to explain things for a beginner to intermediate c# programmer. I’ve seen several blog post that use lambda expressions always assuming the audience is familiar with them. The purpose of this post is to make them simple and easily understood. Let’s begin with a definition. A lambda expression is an anonymous function that can contain expressions and statements, and can be used to create delegates or expression tree types. So anonymous function… delegates or expression tree types? I don’t get it??? Confused yet?   Lets break this into a few definitions and jump right into the code. anonymous function – is an "inline" statement or expression that can be used wherever a delegate type is expected. delegate - is a type that references a method. Once a delegate is assigned a method, it behaves exactly like that method. The delegate method can be used like any other method, with parameters and a return value. Expression trees - represent code in a tree-like data structure, where each node is an expression, for example, a method call or a binary operation such as x < y.   Don’t worry if this still sounds confusing, lets jump right into the code with a simple 3 line program. We are going to use a Function Delegate (all you need to remember is that this delegate returns a value.) Lambda expressions are used most commonly with the Func and Action delegates, so you will see an example of both of these. Lambda Expression 3 lines. using System; using System.Collections.Generic; using System.Linq; using System.Text;   namespace ConsoleApplication7 {     class Program     {          static void Main(string[] args)         {             Func<int, int> myfunc = x => x *x;             Console.WriteLine(myfunc(6).ToString());             Console.ReadLine();         }       } } Is equivalent to Old way of doing it. using System; using System.Collections.Generic; using System.Linq; using System.Text;   namespace ConsoleApplication7 {     class Program     {          static void Main(string[] args)         {               Console.WriteLine(myFunc(6).ToString());             Console.ReadLine();         }            static int myFunc(int x)          {              return x * x;            }       } } In the example, there is a single parameter, x, and the expression is x*x. I’m going to stop here to make sure you are still with me. A lambda expression is an unnamed method written in place of a delegate instance. In other words, the compiler converts the lambda expression to either a : A delegate instance An expression tree All lambda have the following form: (parameters) => expression or statement block Now look back to the ones we have created. It should start to sink in. Don’t get stuck on the => form, use it as an identifier of a lambda. A Lamba expression can also be written in the following form: Lambda Expression. using System; using System.Collections.Generic; using System.Linq; using System.Text;   namespace ConsoleApplication7 {     class Program     {          static void Main(string[] args)         {             Func<int, int> myFunc = x =>             {                 return x * x;             };               Console.WriteLine(myFunc(6).ToString());             Console.ReadLine();         }       } } This form may be easier to read but consumes more space. Lets try an Action delegate – this delegate does not return a value. Action Delegate example. using System; using System.Collections.Generic; using System.Linq; using System.Text;   namespace ConsoleApplication7 {     class Program     {          static void Main(string[] args)         {             Action<string> myAction = (string x) => { Console.WriteLine(x); };             myAction("michael has made this so easy");                                   Console.ReadLine();         }       } } Lambdas can also capture outer variables (such as the example below) A lambda expression can reference the local variables and parameters of the method in which it’s defined. Outer variables referenced by a lambda expression are called captured variables. Capturing Outer Variables using System; using System.Collections.Generic; using System.Linq; using System.Text;   namespace ConsoleApplication7 {     class Program     {          static void Main(string[] args)         {             string mike = "Michael";             Action<string> myAction = (string x) => {                 Console.WriteLine("{0}{1}", mike, x);          };             myAction(" has made this so easy");                                   Console.ReadLine();         }       } } Lamba’s can also with a strongly typed list to loop through a collection.   Used w a strongly typed list. using System; using System.Collections.Generic; using System.Linq; using System.Text;   namespace ConsoleApplication7 {     class Program     {          static void Main(string[] args)         {             List<string> list = new List<string>() { "1", "2", "3", "4" };             list.ForEach(s => Console.WriteLine(s));             Console.ReadLine();         }       } } Outputs: 1 2 3 4 I think this will get you started with Lambda’s, as always consult the MSDN documentation for more information. Still confused? Hopefully you are not.

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• Handy Generic JQuery Functions

  - by Steve Wilkes

  I was a bit of a late-comer to the JQuery party, but now I've been using it for a while it's given me a host of options for adding extra flair to the client side of my applications. Here's a few generic JQuery functions I've written which can be used to add some neat little features to a page. Just call any of them from a document ready function. Apply JQuery Themeroller Styles to all Page Buttons   The JQuery Themeroller is a great tool for creating a theme for a site based on colours and styles for particular page elements. The JQuery.UI library then provides a set of functions which allow you to apply styles to page elements. This function applies a JQuery Themeroller style to all the buttons on a page - as well as any elements which have a button class applied to them - and then makes the mouse pointer turn into a cursor when you mouse over them: function addCursorPointerToButtons() {     $("button, input[type='submit'], input[type='button'], .button") .button().css("cursor", "pointer"); } Automatically Remove the Default Value from a Select Box   Required drop-down select boxes often have a default option which reads 'Please select...' (or something like that), but once someone has selected a value, there's no need to retain that. This function removes the default option from any select boxes on the page which have a data-val-remove-default attribute once one of the non-default options has been chosen: function removeDefaultSelectOptionOnSelect() {     $("select[data-val-remove-default='']").change(function () {         var sel = $(this);         if (sel.val() != "") { sel.children("option[value='']:first").remove(); }     }); } Automatically add a Required Label and Stars to a Form   It's pretty standard to have a little * next to required form field elements. This function adds the text * Required to the top of the first form on the page, and adds *s to any element within the form with the class editor-label and a data-val-required attribute: function addRequiredFieldLabels() {     var elements = $(".editor-label[data-val-required='']");     if (!elements.length) { return; }     var requiredString = "<div class='editor-required-key'>* Required</div>";     var prependString = "<span class='editor-required-label'> * </span>"; var firstFormOnThePage = $("form:first");     if (!firstFormOnThePage.children('div.editor-required-key').length) {         firstFormOnThePage.prepend(requiredString);     }     elements.each(function (index, value) { var formElement = $(this);         if (!formElement.children('span.editor-required-label').length) {             formElement.prepend(prependString);         }     }); } I hope those come in handy :)

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• WebLogic Server internal server error [migrated]

  - by Abhinav Pandey

  When I deployed a project in Apache Tomcat 6.0 it is working fine. When I deployed a same project in WebLogic Server 10.3 it's showing an error: Error 500--Internal Server Error javax.servlet.ServletException: [HTTP:101249][weblogic.servlet.internal.WebAppServletContext@ae43b8 - appName: '_appsdir_ab_dir', name: 'ab', context-path: '/ab', spec-version: 'null']: Servlet class FirstServlet for servlet FirstServlet could not be loaded because the requested class was not found in the classpath . java.lang.UnsupportedClassVersionError: FirstServlet : Unsupported major.minor version 51.0.

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• Using NBuilder to mock up a data driven UI - Part 2

  In this article we will continue our discussion by filling out the implementation in our service class with some NBuilder code. Once we have the working service class in place we can then create a working UI (in the ASP.NET MVC project we created in the last article).

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• Why does my int, booleans, doubles does not work?

  - by SystemNetworks

  As you see, my code does not work. When armor1 is true, it would add my life. goldA is another class. public void goldenArmor(GameContainer gc, StateBasedGame sbg, Graphics g) { if(armor1==true) { goldA.life = life; goldA.intelligence = intelligence; goldA.power = power; goldA.lifeLeft = lifeLeft; goldA.head(); goldA.body(); goldA.legs(); } } My other class: package javagame; import org.newdawn.slick.GameContainer; import org.newdawn.slick.Graphics; import org.newdawn.slick.Image; import org.newdawn.slick.Input; import org.newdawn.slick.SlickException; /* Note: Copyright(C)2012 System Networks | Square NET | Julius Bryan Gambe. You cannot copy the style, story of the game and gameplay! To programmers: The int,doubles,strings,booleans are properly sorted out. Please don't mess it up. */ /* NOTE: We have loops but not for programming. The loop is: 1.show the world to user 2.Obtain input from the user 3.Shows the update, repeat step 1 */ import org.newdawn.slick.*; import org.newdawn.slick.state.*; import org.lwjgl.input.Mouse; //contents: // public class GoldenArmor{ //get it from play public int life; public double intelligence; public int lifeLeft; public double power; public GoldenArmor() { // TODO Auto-generated constructor stub } //start here public void head() { life += 10; intelligence +=0.5; } public void body() { lifeLeft += 100; } public void legs() { power += 100; } } /* SYSTEM NETWORKS(C) 2012 NET FRONT */ The life, intelligence, power, lifeLeft are nothing but to use it as just reference to prevent stack overflow. And at my main class, it becomes my real booleans, int, doubles. How do I fix this? It does not add it to my normal int.

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• Halloween: Season for Java Embedded Internet of Spooky Things (IoST) (Part 4)

  - by hinkmond

  And now here's the Java code that you'll need to read your ghost sensor on your Raspberry Pi The general idea is that you are using Java code to access the GPIO pin on your Raspberry Pi where the ghost sensor (JFET trasistor) detects minute changes in the electromagnetic field near the Raspberry Pi and will change the GPIO pin to high (+3 volts) when something is detected, otherwise there is no value (ground). Here's that Java code: try { /*** Init GPIO port(s) for input ***/ // Open file handles to GPIO port unexport and export controls FileWriter unexportFile = new FileWriter("/sys/class/gpio/unexport"); FileWriter exportFile = new FileWriter("/sys/class/gpio/export"); for (String gpioChannel : GpioChannels) { System.out.println(gpioChannel); // Reset the port File exportFileCheck = new File("/sys/class/gpio/gpio"+gpioChannel); if (exportFileCheck.exists()) { unexportFile.write(gpioChannel); unexportFile.flush(); } // Set the port for use exportFile.write(gpioChannel); exportFile.flush(); // Open file handle to input/output direction control of port FileWriter directionFile = new FileWriter("/sys/class/gpio/gpio" + gpioChannel + "/direction"); // Set port for input directionFile.write(GPIO_IN); } /*** Read data from each GPIO port ***/ RandomAccessFile[] raf = new RandomAccessFile[GpioChannels.length]; int sleepPeriod = 10; final int MAXBUF = 256; byte[] inBytes = new byte[MAXBUF]; String inLine; int zeroCounter = 0; // Get current timestamp with Calendar() Calendar cal; DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss.SSS"); String dateStr; // Open RandomAccessFile handle to each GPIO port for (int channum=0; channum And, then we just load up our Java SE Embedded app, place each Raspberry Pi with a ghost sensor attached in strategic locations around our Santa Clara office (which apparently is very haunted by ghosts from the Agnews Insane Asylum 1906 earthquake), and watch our analytics for any ghosts. Easy peazy. See the previous posts for the full series on the steps to this cool demo: Halloween: Season for Java Embedded Internet of Spooky Things (IoST) (Part 1) Halloween: Season for Java Embedded Internet of Spooky Things (IoST) (Part 2) Halloween: Season for Java Embedded Internet of Spooky Things (IoST) (Part 3) Halloween: Season for Java Embedded Internet of Spooky Things (IoST) (Part 4) Hinkmond

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• My schoolmates are playing too much and talk loudly, what should I do ? report them ? [closed]

  - by jokoon

  I'm a in a private game programming school class (there are also 3D/art classes in the school), and at least half or two third of the 12 people in my class play at various games (Age of Empires, web games, online card games, etc). They are talking quite loudly on top of that, and I'm getting hard times trying to concentrate: it feels like I'm in a cybercafe full of teenagers. I don't know if I have Hyperacusis (http://en.wikipedia.org/wiki/Hyperacusis),

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• How do you handle objects that need custom behavior, and need to exist as an entity in the database?

  - by Scott Whitlock

  For a simple example, assume your application sends out notifications to users when various events happen. So in the database I might have the following tables: TABLE Event EventId uniqueidentifier EventName varchar TABLE User UserId uniqueidentifier Name varchar TABLE EventSubscription EventUserId EventId UserId The events themselves are generated by the program. So there are hard-coded points in the application where an event instance is generated, and it needs to notify all the subscribed users. So, the application itself doesn't edit the Event table, except during initial installation, and during an update where a new Event might be created. At some point, when an event is generated, the application needs to lookup the Event and get a list of Users. What's the best way to link the event in the source code to the event in the database? Option 1: Store the EventName in the program as a fixed constant, and look it up by name. Option 2: Store the EventId in the program as a static Guid, and look it up by ID. Extra Credit In other similar circumstances I may want to include custom behavior with the event type. That is, I'll want subclasses of my Event entity class with different behaviors, and when I lookup an event, I want it to return an instance of my subclass. For instance: class Event { public Guid Id { get; } public Guid EventName { get; } public ReadOnlyCollection<EventSubscription> EventSubscriptions { get; } public void NotifySubscribers() { foreach(var eventSubscription in EventSubscriptions) { eventSubscription.Notify(); } this.OnSubscribersNotified(); } public virtual void OnSubscribersNotified() {} } class WakingEvent : Event { private readonly IWaker waker; public WakingEvent(IWaker waker) { if(waker == null) throw new ArgumentNullException("waker"); this.waker = waker; } public override void OnSubscribersNotified() { this.waker.Wake(); base.OnSubscribersNotified(); } } So, that means I need to map WakingEvent to whatever key I'm using to look it up in the database. Let's say that's the EventId. Where do I store this relationship? Does it go in the event repository class? Should the WakingEvent know declare its own ID in a static member or method? ...and then, is this all backwards? If all events have a subclass, then instead of retrieving events by ID, should I be asking my repository for the WakingEvent like this: public T GetEvent<T>() where T : Event { ... // what goes here? ... } I can't be the first one to tackle this. What's the best practice?

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• Win 2 years free web hosting for your site!!!

  - by mcp111

  EggHeadCafe is giving away a free 2 year Personal Class Account to Arvixe ASP.NET Web Hosting! In fact, all members who enter the drawing below win a 20% discount off a Personal Class Account. The nice thing about Arvixe is that they also accept Google checkout and Paypal. http://www.eggheadcafe.com/tutorials/aspnet/828f2029-b7be-4d15-877c-0d9e9ab74fc5/review-of-arvixecom-web-site-hosting.aspx  Tweet

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• Java: How to manage UDP client-server state

  - by user92947

  I am trying to write a Java application that works similar to MapReduce. There is a server and several workers. Workers may come and go as they please and the membership to the group has a soft-state. To become a part of the group, the worker must send a UDP datagram to the server, but to continue to be part of the group, the worker must send the UDP datagram to the server every 5 minutes. In order to accommodate temporary errors, a worker is allowed to miss as many as two consecutive periodic UDP datagrams. So, the server must keep track of the current set of workers as well as the last time each worker had sent a UDP datagram. I've implemented a class called WorkerListener that implements Runnable and listens to UDP datagrams on a particular UDP port. Now, to keep track of active workers, this class may maintain a HashSet (or HashMap). When a datagram is received, the server may query the HashSet to check if it is a new member. If so, it can add the new worker to the group by adding an entry into the HashSet. If not, it must reset a "timer" for the worker, noting that it has just heard from the corresponding worker. I'm using the word timer in a generic sense. It doesn't have to be a clock of sorts. Perhaps this could also be implemented using int or long variables. Also, the server must run a thread that continuously monitors the timers for the workers to see that a client that times out on two consecutive datagram intervals, it is removed from the HashSet. I don't want to do this in the WorkerListener thread because it would be blocking on the UDP datagram receive() function. If I create a separate thread to monitor the worker HashSet, it would need to be a different class, perhaps WorkerRegistrar. I must share the HashSet with that thread. Mutual exclusion must also be implemented, then. My question is, what is the best way to do this? Pointers to some sample implementation would be great. I want to use the barebones JDK implementation, and not some fancy state maintenance API that takes care of everything, because I want this to be a useful demonstration for a class that I am teaching. Thanks

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• What is a good resource for learning how the .Net Framework works? [on hold]

  - by Till Death Developer

  I've been developing web apps, for a while now so i know how to get the job done, what i don't know is how every thing really works, i know some but the rest i can't get a grasp on like how abstract works, what happens when i instantiate an object from a class that inherits from an abstract class?, where things get stored Heap vs Stack?, in other words the Interview questions that i suck at, so any advice would be great, books, videos, online courses, whatever you can provide would really help me.

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• Using elapsed time for SlowMo in XNA

  - by Dave Voyles

  I'm trying to create a slow-mo effect in my pong game so that when a player is a button the paddles and ball will suddenly move at a far slower speed. I believe my understanding of the concepts of adjusting the timing in XNA are done, but I'm not sure of how to incorporate it into my design exactly. The updates for my bats (paddles) are done in my Bat.cs class: /// Controls the bat moving up the screen /// </summary> public void MoveUp() { SetPosition(Position + new Vector2(0, -moveSpeed)); } /// <summary> /// Controls the bat moving down the screen /// </summary> public void MoveDown() { SetPosition(Position + new Vector2(0, moveSpeed)); } /// <summary> /// Updates the position of the AI bat, in order to track the ball /// </summary> /// <param name="ball"></param> public virtual void UpdatePosition(Ball ball) { size.X = (int)Position.X; size.Y = (int)Position.Y; } While the rest of my game updates are done in my GameplayScreen.cs class (I'm using the XNA game state management sample) Class GameplayScreen { ........... bool slow; .......... public override void Update(GameTime gameTime, bool otherScreenHasFocus, bool coveredByOtherScreen) base.Update(gameTime, otherScreenHasFocus, false); if (IsActive) { // SlowMo Stuff Elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds; if (Slowmo) Elapsed *= .8f; MoveTimer += Elapsed; double elapsedTime = gameTime.ElapsedGameTime.TotalMilliseconds; if (Keyboard.GetState().IsKeyDown(Keys.Up)) slow = true; else if (Keyboard.GetState().IsKeyDown(Keys.Down)) slow = false; if (slow == true) elapsedTime *= .1f; // Updating bat position leftBat.UpdatePosition(ball); rightBat.UpdatePosition(ball); // Updating the ball position ball.UpdatePosition(); and finally my fixed time step is declared in the constructor of my Game1.cs Class: /// <summary> /// The main game constructor. /// </summary> public Game1() { IsFixedTimeStep = slow = false; } So my question is: Where do I place the MoveTimer or elapsedTime, so that my bat will slow down accordingly?

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• Do any OO languages support a mechanism to guarantee an overriden method will call the base?

  - by Aaron Anodide

  I think this might be a useful language feature and was wondering if any languages already support it. The idea is if you have: class C virtual F statement1 statement2 and class D inherits C override F statement1 statement2 C.F() There would be a keyword applied to C.F() such that removing the last line of code above would cause a compiler error because it's saying "This method can be overridden but the implementation here needs to run no matter what".

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• Sharing on Github

  - by Alan

  Over the past couple weeks I have gotten a lot of help from StackOverflow users on a project, and rather than keep the finished product to myself I wanted to share it unencumbered by licenses, but don't want there to be so much legwork during installation that users shy away from trying it. I am about to post it to Github and choosing public domain licensing. I would like to to be super simple for users to make use of and just FTP it up and go. That being said, do I need to make sure I remove things like the JQuery file, and other GPL / MIT licensed dependencies that I didn't write but that my code depends on? I haven't removed any copyright notices from the other code and all of it open source, it would just be nice if users could download everything at once while of course not trying to represent that I am the license holder of the dependencies. Inside my files are also some snippets, do those have to be externalized with installation instructions or can it be posted as is? Here is an example, my nav.php file is 115 lines long and I have these at the top: <script type="text/javascript" src="./js/ddaccordion.js"> /*********************************************** * Accordion Content script- (c) Dynamic Drive DHTML code library (www.dynamicdrive.com) * Visit http://www.dynamicDrive.com for hundreds of DHTML scripts * This notice must stay intact for legal use ***********************************************/ </script> <link href="css/admin.css" rel="stylesheet"> <script type="text/javascript"> ddaccordion.init({ headerclass: "submenuheader", //Shared CSS class name of headers group contentclass: "submenu", //Shared CSS class name of contents group revealtype: "click", //Reveal content when user clicks or onmouseover the header? Valid value: "click", "clickgo", or "mouseover" mouseoverdelay: 200, //if revealtype="mouseover", set delay in milliseconds before header expands onMouseover collapseprev: false, //Collapse previous content (so only one open at any time)? true/false defaultexpanded: [], //index of content(s) open by default [index1, index2, etc] [] denotes no content onemustopen: false, //Specify whether at least one header should be open always (so never all headers closed) animatedefault: false, //Should contents open by default be animated into view? persiststate: true, //persist state of opened contents within browser session? toggleclass: ["", ""], //Two CSS classes to be applied to the header when it's collapsed and expanded, respectively ["class1", "class2"] togglehtml: ["suffix", "<img src='./images/plus.gif' class='statusicon' />", "<img src='./images/minus.gif' class='statusicon' />"], //Additional HTML added to the header when it's collapsed and expanded, respectively ["position", "html1", "html2"] (see docs) animatespeed: "fast", //speed of animation: integer in milliseconds (ie: 200), or keywords "fast", "normal", or "slow" oninit:function(headers, expandedindices){ //custom code to run when headers have initalized //do nothing }, onopenclose:function(header, index, state, isuseractivated){ //custom code to run whenever a header is opened or closed //do nothing } }) </script>

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• Mutable Records in F#

  - by MarkPearl

  I’m loving my expert F# book – today I thought I would give a post on using mutable records as covered in Chapter 4 of Expert F#. So as they explain the simplest mutable data structures in F# are mutable records. The whole concept of things by default being immutable is a new one for me from my C# background. Anyhow… lets look at some C# code first. using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace MutableRecords { public class DiscreteEventCounter { public int Total { get; set; } public int Positive { get; set; } public string Name { get; private set; } public DiscreteEventCounter(string name) { Name = name; } } class Program { private static void recordEvent(DiscreteEventCounter s, bool isPositive) { s.Total += 1; if (isPositive) s.Positive += 1; } private static void reportStatus (DiscreteEventCounter s) { Console.WriteLine("We have {0} {1} out of {2}", s.Positive, s.Name, s.Total); } static void Main(string[] args) { var longCounter = new DiscreteEventCounter("My Discrete Counter"); recordEvent(longCounter, true); recordEvent(longCounter, true); reportStatus(longCounter); Console.ReadLine(); } } } Quite simple, we have a class that has a few values. We instantiate an instance of the class and perform increments etc on the instance. Now lets look at an equivalent F# sample. namespace EncapsulationNS module Module1 = open System type DiscreteEventCounter = { mutable Total : int mutable Positive : int Name : string } let recordEvent (s: DiscreteEventCounter) isPositive = s.Total <- s.Total+1 if isPositive then s.Positive <- s.Positive+1 let reportStatus (s: DiscreteEventCounter) = printfn "We have %d %s out of %d" s.Positive s.Name s.Total let newCounter nm = { Total = 0; Positive = 0; Name = nm } // // Using it... // let longCounter = newCounter "My Discrete Counter" recordEvent longCounter (true) recordEvent longCounter (true) reportStatus longCounter System.Console.ReadLine() Notice in the type declaration of the DiscreteEventCounter we had to explicitly declare that the total and positive value holders were mutable. And that’s it – a very simple example of mutable types.

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• Image first loaded, then it isn't? (XNA)

  - by M0rgenstern

  I am very confused at the Moment. I have the following Class: (Just a part of the class): public class GUIWindow { #region Static Fields //The standard image for windows. public static IngameImage StandardBackgroundImage; #endregion } IngameImage is just one of my own classes, but actually it contains a Texture2D (and some other things). In another class I load a list of GUIButtons by deserializing a XML file. public static GUI Initializazion(string pXMLPath, ContentManager pConMan) { GUI myGUI = pConMan.Load<GUI>(pXMLPath); GUIWindow.StandardBackgroundImage = new IngameImage(pConMan.Load<Texture2D>(myGUI.WindowStandardBackgroundImagePath), Vector2.Zero, 1024, 600, 1, 0, Color.White, 1.0f, true, false, false); System.Console.WriteLine("Image loaded? " + (GUIWindow.StandardBackgroundImage.ImageStrip != null)); myGUI.Windows = pConMan.Load<List<GUIWindow>>(myGUI.GUIFormatXMLPath); System.Console.WriteLine("Windows loaded"); return myGUI; } Here this line: System.Console.WriteLine("Image loaded? " + (GUIWindow.StandardBackgroundImage.ImageStrip != null)); Prints "true". To load the GUIWindows I need an "empty" constructor, which looks like that: public GUIWindow() { Name = ""; Buttons = new List<Button>(); ImagePath = ""; System.Console.WriteLine("Image loaded? (In win) " + (GUIWindow.StandardBackgroundImage.ImageStrip != null)); //Image = new IngameImage(StandardBackgroundImage); //System.Console.WriteLine( //Image.IsActive = false; SelectedButton = null; IsActive = false; } As you can see, I commented lines out in the constructor. Because: Otherwise this would crash. Here the line System.Console.WriteLine("Image loaded? (In win) " + (GUIWindow.StandardBackgroundImage.ImageStrip != null)); Doesn't print anything, it just crashes with the following errormessage: Building content threw NullReferenceException: Object reference not set to an object instance. Why does this happen? Before the program wants to load the List, it prints "true". But in the constructor, so in the loading of the list it prints "false". Can anybody please tell me why this happens and how to fix it?

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• Alternatives to multiple inheritance for my architecture (NPCs in a Realtime Strategy game)?

  - by Brettetete

  Coding isn't that hard actually. The hard part is to write code that makes sense, is readable and understandable. So I want to get a better developer and create some solid architecture. So I want to do create an architecture for NPCs in a video-game. It is a Realtime Strategy game like Starcraft, Age of Empires, Command & Conquers, etc etc.. So I'll have different kinds of NPCs. A NPC can have one to many abilities (methods) of these: Build(), Farm() and Attack(). Examples: Worker can Build() and Farm() Warrior can Attack() Citizen can Build(), Farm() and Attack() Fisherman can Farm() and Attack() I hope everything is clear so far. So now I do have my NPC Types and their abilities. But lets come to the technical / programmatical aspect. What would be a good programmatic architecture for my different kinds of NPCs? Okay I could have a base class. Actually I think this is a good way to stick with the DRY principle. So I can have methods like WalkTo(x,y) in my base class since every NPC will be able to move. But now lets come to the real problem. Where do I implement my abilities? (remember: Build(), Farm() and Attack()) Since the abilities will consists of the same logic it would be annoying / break DRY principle to implement them for each NPC (Worker,Warrior, ..). Okay I could implement the abilities within the base class. This would require some kind of logic that verifies if a NPC can use ability X. IsBuilder, CanBuild, .. I think it is clear what I want to express. But I don't feel very well with this idea. This sounds like a bloated base class with too much functionality. I do use C# as programming language. So multiple inheritance isn't an opinion here. Means: Having extra base classes like Fisherman : Farmer, Attacker won't work.

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• Why enumerator structs are a really bad idea

  If you've ever poked around the .NET class libraries in Reflector, you probably would have noticed that the generic collection classes all have implementations of their IEnumerator as a struct rather than a class. As you will see, this design decision has some rather unfortunate side effects......Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Savable in Widget Lookup on Move Action

  - by Geertjan

  Possible from 7.3 onwards, since Widget now implements Lookup.Provider for the first time: import java.awt.Point; import java.io.IOException; import org.netbeans.api.visual.action.ActionFactory; import org.netbeans.api.visual.action.MoveProvider; import org.netbeans.api.visual.widget.LabelWidget; import org.netbeans.api.visual.widget.Scene; import org.netbeans.api.visual.widget.Widget; import org.netbeans.spi.actions.AbstractSavable; import org.openide.util.Lookup; import org.openide.util.lookup.AbstractLookup; import org.openide.util.lookup.InstanceContent; import org.openide.windows.TopComponent; public class MyWidget extends LabelWidget { private MySavable mySavable; private Lookup lookup; private TopComponent tc; private InstanceContent ic; public MyWidget(Scene scene, String label, TopComponent tc) { super(scene, label); this.tc = tc; ic = new InstanceContent(); getActions().addAction(ActionFactory.createMoveAction(null, new MoveStrategyProvider())); } @Override public Lookup getLookup() { if (lookup == null) { lookup = new AbstractLookup(ic); } return lookup; } private class MoveStrategyProvider implements MoveProvider { @Override public void movementStarted(Widget widget) { } @Override public void movementFinished(Widget widget) { modify(); } @Override public Point getOriginalLocation(Widget widget) { return ActionFactory.createDefaultMoveProvider().getOriginalLocation(widget); } @Override public void setNewLocation(Widget widget, Point point) { ActionFactory.createDefaultMoveProvider().setNewLocation(widget, point); } } private void modify() { if (getLookup().lookup(MySavable.class) == null) { ic.add(mySavable = new MySavable()); } } private class MySavable extends AbstractSavable { public MySavable() { register(); } TopComponent tc() { return tc; } @Override protected String findDisplayName() { return getLabel(); } @Override protected void handleSave() throws IOException { ic.remove(mySavable); unregister(); } @Override public boolean equals(Object obj) { if (obj instanceof MySavable) { MySavable m = (MySavable) obj; return tc() == m.tc(); } return false; } @Override public int hashCode() { return tc().hashCode(); } } }

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• How to save and retrieve data as key-value pairs or files in isolated storage?

  - by kaleidoscope

  One can use isolated storage to store data locally on the user's computer. There are two ways to use isolated storage. The first way is to save or retrieve data as key/value pairs by using the IsolatedStorageSettings class. The second way is to save or retrieve files by using the IsolatedStorageFile class. More details can be found at http://silverlight.net/learn/quickstarts/isolatedstorage/   Rituraj, J

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• Any ideas on reducing lag in terrain generation?

  - by l5p4ngl312

  Ok so here's the deal. I've written an isometric engine that generates terrain based on camera values using 2D perlin noise. I planned on doing 3D but first I need to work out the lag issues I'm having. I will try to explain how I am doing this so that maybe someone can spot where I am going wrong. I know it should not be this laggy. There is the abstract class Block which right now just contains render(). BlockGrass, etc. extend this class and each has code in the render function to create a textured quad at the given position. Then there is the class Chunk which has the function Generate() and setBlocksInArea(). Generate uses 2D perlin noise to make a height map and stores the heights in a 2D array. It stores the positions of each block it generates in blockarray[x][y][z]. The chunks are 8x8x128. In the main game class there is a 3D array called blocksInArea. The blocks in this array are what gets rendered. When a chunk generates, it adds its blocks to this array at the correct index. It is like this so chunks can be saved to the hard drive (even though they aren't yet) but there can still be optimization with the rendering that you wouldn't have if you rendered each chunk separately. Here's where the laggy part comes in: When the camera moves to a new chunk, a row of chunks generates on the end of the axis that the camera moved on. But it still has to move the other chunks up/down in the blocksInArea (render) array. It does this by calculating the new position in the array and doing the Chunk.setBlocksInArea(): for(int x = 0; x < 8; x++){ for(int y = 0; y < 8; y++){ nx = x+(coordX - camCoordX)*8 ny = y+(coordY - camCoordY)*8 for(int z = 0; z < height[x][y]; z++){ blockarray[x][y][z] = Game.blocksInArea[nx][ny][z]; } } } My reasoning was that this would be much faster than doing the perlin noise all over again, but there are still little spikes of lag when you move in between chunks. Edit: Would it be possible to create a 3 dimensional array list so that shifting of chunks within the array would not be neccessary?

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• Write Your Own Microsoft Expression Blend 3 Addin

  Although there have been numerous articles introducing how to write a Microsoft Expression blend 2 addin, the Microsoft Expression blend 3/4 related ones are few. In this article, you will learn what a Microsoft Expression blend addin is and command the common routine to write an Addin. Finally, you will master the inner workings of the addin through a concrete sample application.

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• Different bounding volumes for culling and collision detection

  - by Serthy

  Should an object in a 3D-engine use different bounding volumes for collision-detection (broad-phase) and culling? Basically class renderBounds and class physBounds versus class boundingVolume? Each of this classes then could either contain the same type of volumes (AABB's, kDOP's, sphere's etc.) or a special fitting one for the particular object. (note: without considering of using an external physics engine)

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• Achieving decoupling in Model classes

  - by Guven

  I am trying to test-drive (or at least write unit tests) my Model classes but I noticed that my classes end up being too coupled. Since I can't break this coupling, writing unit tests is becoming harder and harder. To be more specific: Model Classes: These are the classes that hold the data in my application. They resemble pretty much the POJO (plain old Java objects), but they also have some methods. The application is not too big so I have around 15 model classes. Coupling: Just to give an example, think of a simple case of Order Header - Order Item. The header knows the item and the item knows the header (needs some information from the header for performing certain operations). Then, let's say there is the relationship between Order Item - Item Report. The item report needs the item as well. At this point, imagine writing tests for Item Report; you need have a Order Header to carry out the tests. This is a simple case with 3 classes; things get more complicated with more classes. I can come up with decoupled classes when I design algorithms, persistence layers, UI interactions, etc... but with model classes, I can't think of a way to separate them. They currently sit as one big chunk of classes that depend on each other. Here are some workarounds that I can think of: Data Generators: I have a package that generates sample data for my model classes. For example, the OrderHeaderGenerator class creates OrderHeaders with some basic data in it. I use the OrderHeaderGenerator from my ItemReport unit-tests so that I get an instance to OrderHeader class. The problem is these generators get complicated pretty fast and then I also need to test these generators; defeating the purpose a little bit. Interfaces instead of dependencies: I can come up with interfaces to get rid of the hard dependencies. For example, the OrderItem class would depend on the IOrderHeader interface. So, in my unit tests, I can easily mock the behaviour of an OrderHeader with a FakeOrderHeader class that implements the IOrderHeader interface. The problem with this approach is the complexity that the Model classes would end up having. Would you have other ideas on how to break this coupling in the model classes? Or, how to make it easier to unit-test the model classes?

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