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  • Variable scope and the 'using' statement in .NET

    - by pete the pagan-gerbil
    If a variable is at class level (ie, private MyDataAccessClass _dataAccess;, can it be used as part of a using statement within the methods of that class to dispose of it correctly? Is it wise to use this method, or is it better to always declare a new variable with a using statement (ie, using (MyDataAccessClass dataAccess = new MyDataAccessClass()) instead of using (_dataAccess = new MyDataAccessClass()))?

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  • Refactoring Singleton Overuse

    - by drharris
    Today I had an epiphany, and it was that I was doing everything wrong. Some history: I inherited a C# application, which was really just a collection of static methods, a completely procedural mess of C# code. I refactored this the best I knew at the time, bringing in lots of post-college OOP knowledge. To make a long story short, many of the entities in code have turned out to be Singletons. Today I realized I needed 3 new classes, which would each follow the same Singleton pattern to match the rest of the software. If I keep tumbling down this slippery slope, eventually every class in my application will be Singleton, which will really be no logically different from the original group of static methods. I need help on rethinking this. I know about Dependency Injection, and that would generally be the strategy to use in breaking the Singleton curse. However, I have a few specific questions related to this refactoring, and all about best practices for doing so. How acceptable is the use of static variables to encapsulate configuration information? I have a brain block on using static, and I think it is due to an early OO class in college where the professor said static was bad. But, should I have to reconfigure the class every time I access it? When accessing hardware, is it ok to leave a static pointer to the addresses and variables needed, or should I continually perform Open() and Close() operations? Right now I have a single method acting as the controller. Specifically, I continually poll several external instruments (via hardware drivers) for data. Should this type of controller be the way to go, or should I spawn separate threads for each instrument at the program's startup? If the latter, how do I make this object oriented? Should I create classes called InstrumentAListener and InstrumentBListener? Or is there some standard way to approach this? Is there a better way to do global configuration? Right now I simply have Configuration.Instance.Foo sprinkled liberally throughout the code. Almost every class uses it, so perhaps keeping it as a Singleton makes sense. Any thoughts? A lot of my classes are things like SerialPortWriter or DataFileWriter, which must sit around waiting for this data to stream in. Since they are active the entire time, how should I arrange these in order to listen for the events generated when data comes in? Any other resources, books, or comments about how to get away from Singletons and other pattern overuse would be helpful.

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  • Object Deletion: use parent or not

    - by metdos
    Which one do you prefer to delete objects? Especially in QT, but other practices are also welcome. These two alternatives seem same to me, are they? 1.Bound to another class, and destroy when it is destroyed. SomeClass::SomeClass{ socket_ = new QTcpSocket(this); } or 2.Destroy in the destructor of class SomeClass::SomeClass{ socket_ = new QTcpSocket(); } SomeClass::~SomeClass{ delete socket_; }

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  • Get with the ajax data into a php file

    - by Max Torstensson
    I'm trying to build a login system with ajax and php. I use a log-view where I then save the data in ajax which brings into my doLogin.php (php file). My problem is that php file should never be any ajax data for when I build it into a class and a function VIEW: public function DoLoginBox() { //inloggning form-tagg... return '<p>&nbsp;</p> <div id="content"> <h1>Login Form</h1> <form id="form1" name="form1" action="Handler/doLogin.php" method="post"> <p> <label for="username">Username: </label> <input type="text" name="username" id="username" /> </p> <p> <label for="password">Password: </label> <input type="password" name="password" id="password" /> </p> <p> <input type="submit" id="login" name="login" /> </p> </form> <div id="message"></div> </div>'; } AJAX: <script type="text/javascript"> $(document).ready(function() { $("#login").click(function() { var action = $("#form1").attr('action'); var form_data = { username: $("#username").val(), password: $("#password").val(), is_ajax: 1 }; $.ajax({ type: "POST", url: action, data: form_data, success: function(response) { if(response == 'success') $("#form1").slideUp('slow', function() { $("#message").html("<p class='success'>You have logged in successfully!</p>"); }); else $("#message").html("<p class='error'>Invalid username and/or password.</p>"); } }); return false; }); }); </script PHP: <?php require_once ("UserHandler.php"); class DoLogingHandler{ public function Login (){ $is_ajax = !empty($_REQUEST['is_ajax']); if(isset($is_ajax) && $is_ajax) { $username = $_REQUEST['username']; $password = $_REQUEST['password']; $UserHandler = new UserHandler(); $UserHandler -> controllDB($username,$password); if($username == 'demo' && $password == 'demo') { echo "success"; } } } } ` $DoLogingHandler = new DoLogingHandler(); $DoLogingHandler-Login(); ?

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  • c# Lambda Expression built with LinqKit does not compile

    - by Frank Michael Kraft
    This lambda does not compile, but I do not understand why. using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Linq.Expressions; using LinqKit; namespace ConsoleApplication2 { class Program { static void Main(string[] args) { var barModel = new BarModel(); string id = "some"; Console.WriteLine(barModel.subFor(id).ToString()); // output: m => (True AndAlso (m.key == value(ConsoleApplication2.Bar`1+<>c__DisplayClass0[ConsoleApplication2.Model]).id)) Console.ReadKey(); var subworkitems = barModel.list.Where(barModel.subFor(id).Compile()); // Exception {"variable 'm' of type 'ConsoleApplication2.Model' referenced from scope '', but it is not defined"} Console.WriteLine(subworkitems.ToString()); Console.ReadKey(); } } class Bar<TModel> { public Bar(Expression<Func<TModel, string>> foreignKeyExpression) { _foreignKeyExpression = foreignKeyExpression; } private Expression<Func<TModel, string>> _foreignKeyExpression { get; set; } public Expression<Func<TModel, bool>> subFor(string id) { var ex = forTargetId(id); return ex; } public Expression<Func<TModel, bool>> forTargetId(String id) { var fc = _foreignKeyExpression; Expression<Func<TModel, bool>> predicate = m => true; var result = predicate.And(m => fc.Invoke(m) == id).Expand(); return result; } } class Model { public string key; public string value; } class BarModel : Bar<Model> { public List<Model> list; public BarModel() : base(m => m.key) { list = new List<Model>(); } } }

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  • display:none and scrolling text

    - by small
    There is a conflict between display:none and scrolling text. What can I use instead of using display:none? <div id="side_forums_pane" class="side_pane" style=" height:350px;width:260px"> <div class="jscroller2_up jscroller2_speed-19 jscroller2_mousemove" style="height:250px;width:260px;"> </div> </div>

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  • Java homework help, Error <identifier> expected

    - by user2900126
    Help with java homework this is my assignment that I have, this assignment code I've tried. But when I try to compile it I keep getting errors which I cant seem to find soloutions too: Error says <identifier> expected for Line 67 public static void () Assignment brief To write a simple java classMobile that models a mobile phone. Details the information stored about each mobile phone will include • Its type e.g. “Sony ericsson x90” or “Samsung Galaxy S”; • Its screen size in inches; You may assume that this a whole number from the scale 3 to 5 inclusive. • Its memory card capacity in gigabytes You may assume that this a whole number • The name of its present service provider You may assume this is a single line of text. • The type of contract with service provider You may assume this is a single line of text. • Its camera resolution in megapixels; You should not assume that this a whole number; • The percentage of charge left on the phone e.g. a fully charged phone will have a charge of 100. You may assume that this a whole number • Whether the phone has GPS or not. Your class will have fields corresponding to these attributes . Start by opening BlueJ, creating a new project called myMobile which has a classMobile and set up the fields that you need, Next you will need to write a Constructor for the class. Assume that each phone is manufactured by creating an object and specifying its type, its screen size, its memory card capacity, its camera resolution and whether it has GPS or not. Therefore you will need a constructor that allows you to pass arguments to initialise these five attributes. Other fields should be set to appropriate default values. You may assume that a new phone comes fully charged. When the phone is sold to its owner, you will need to set the service provider and type of contract with that provider so you will need mutator methods • setProvider () - - to set service provider. • setContractType - - to set the type of contract These methods will be used when the phones provider is changed. You should also write a mutator method ChargeUp () which simulates fully charging the phone. To obtain information about your mobile object you should write • accessor methods corresponding to four of its fields: • getType () – which returns the type of mobile; • getProvider () – which returns the present service provider; • getContractType () – which returns its type of contract; • getCharge () – which returns its remaining charge. An accessor method to printDetails () to print, to the terminal window, a report about the phone e.g. This mobile phone is a sony Erricsson X90 with Service provider BigAl and type of contract PAYG. At present it has 30% of its battery charge remaining. Check that the new method works correctly by for example, • creating a Mobile object and setting its fields; • calling printDetails () and t=checking the report corresponds to the details you have just given the mobile; • changing the service provider and contract type by calling setprovider () and setContractType (); • calling printDetails () and checking the report now prints out the new details. Challenging excercises • write a mutator methodswitchedOnFor () =which simulates using the phone for a specified period. You may assume the phone loses 1% of its charge for each hour that it is switched on . • write an accessor method checkcharge () whichg checks the phone remaing charge. If this charge has a value less than 25%, then this method returns a string containg the message Be aware that you will soon need to re-charge your phone, otherwise it returns a string your phone charge is sufficient. • Write a method changeProvider () which simulates changing the provider (and presumably also the type of service contract). Finally you may add up to four additional fields, with appropriate methods, that might be required in a more detailed model. above is my assignment that I have, this assignment code I've tried. But when I try to oompile it I keep getting errors which I cant seem to find soloutions too: Error says <identifier> expected for Line 67 public static void () /** * to write a simple java class Mobile that models a mobile phone. * * @author (Lewis Burte-Clarke) * @version (14/10/13) */ public class Mobile { // type of phone private String phonetype; // size of screen in inches private int screensize; // menory card capacity private int memorycardcapacity; // name of present service provider private String serviceprovider; // type of contract with service provider private int typeofcontract; // camera resolution in megapixels private int cameraresolution; // the percentage of charge left on the phone private int checkcharge; // wether the phone has GPS or not private String GPS; // instance variables - replace the example below with your own private int x; // The constructor method public Mobile(String mobilephonetype, int mobilescreensize, int mobilememorycardcapacity,int mobilecameraresolution,String mobileGPS, String newserviceprovider) { this.phonetype = mobilephonetype; this.screensize = mobilescreensize; this.memorycardcapacity = mobilememorycardcapacity; this.cameraresolution = mobilecameraresolution; this.GPS = mobileGPS; // you do not use this ones during instantiation,you can remove them if you do not need or assign them some default values //this.serviceprovider = newserviceprovider; //this.typeofcontract = 12; //this.checkcharge = checkcharge; Mobile samsungPhone = new Mobile("Samsung", "1024", "2", "verizon", "8", "GPS"); 1024 = screensize; 2 = memorycardcapacity; 8 = resolution; GPS = gps; "verizon"=serviceprovider; //typeofcontract = 12; //checkcharge = checkcharge; } // A method to display the state of the object to the screen public void displayMobileDetails() { System.out.println("phonetype: " + phonetype); System.out.println("screensize: " + screensize); System.out.println("memorycardcapacity: " + memorycardcapacity); System.out.println("cameraresolution: " + cameraresolution); System.out.println("GPS: " + GPS); System.out.println("serviceprovider: " + serviceprovider); System.out.println("typeofcontract: " + typeofcontract); } /** * The mymobile class implements an application that * simply displays "new Mobile!" to the standard output. */ public class mymobile { public static void main(String[] args) { System.out.println("new Mobile!"); //Display the string. } } public static void buildPhones(){ Mobile Samsung = new Mobile("Samsung", "3.0", "4gb", "8mega pixels", "GPS"); Mobile Blackberry = new Mobile("Blackberry", "3.0", "4gb", "8mega pixels", "GPS"); Samsung.displayMobileDetails(); Blackberry.displayMobileDetails(); } public static void main(String[] args) { buildPhones(); } } any answers.replies and help would be greatly appreciated as I really lost!

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  • Singleton & Multithreading in Java

    - by vivek jagtap
    What is the preferred way to work with Singleton class in multithreaded environment? Suppose if I have 3 thread, and all they try to access getInstance() method of singleton class at the same time - What would happen if no synchronization is maintained? Is it good practice to use synchronized getInstance() method or use synchronized block inside getInstance(). Please advise if there is any other way out.

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  • Flex: Constant strings in metadata

    - by Daniel Engmann
    I have something like public class Controller { [Observer("fetchEmployeesEvent")] public function fetchEmployees() : void { //doSomething } } and I want something like public class Controller { public static const FETCH_EMPLOYEES_EVENT : String = "fetchEmployeesEvent"; [Observer(FETCH_EMPLOYEES_EVENT)] public function fetchEmployees() : void { //doSomething } } My problem is that only the first code snippet works. Flex seems to ignore the constant FETCH_EMPLOYEES_EVENT in the metadata-tag. My question is: Is it somehow possible to use constant strings in metadata?

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  • variables reference value of string

    - by xdevel2000
    How can I get the reference value of a string object? If I hava a class like class T() { } T t = new T(); System.out.println( t); print out T@a3455467 that is the reference value inside t but for string? maybe with method hashCode()??

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  • Difference in displaying inner div between IE and Chrome

    - by Gaara
    I have this code that has one "outerDIV" that contains an "innerDIV". On chrome the "innerDIV" size is 491px, whereas on IE it is 425px (same as outerDIV). Hence, on Chrome I can see the first two children of "innerdiv": "My test string #1" and "test2". But for IE I can only see the first child. I am not quite sure what the "right" behavior should be, as firefox does the same as IE. However I would like to have IE do the same as Chrome. I have been experimenting with some css styles (mainly overflow and display), but still can't make it right: IE will expand its height instead of its width to make the elements fit. Can you guys help me figure out a way to change the css so that IE will wraps the div elements inline? As a restriction though, I cannot change the width on the HTML. As a benefit, I am using a css that only loads for IE to patch these kind of IE inconsistencies. The same css will NOT load for chrome, so I don't need to worry about messing with chrome when changing the IE CSS. Thanks in advance! <html> <head> <style type="text/css"> <!-- body { font-family: helvetica; } .myContainer { overflow: hidden; border: 1px solid rgba(0, 0, 0, .5); font-size: 14pt; height: 49px; line-height: 49px; overflow: hidden; display: block; } .myContainer > DIV { float: left; white-space: nowrap; display: block; } .myContainer .item:first-child { padding-left: 10px; } .myContainer .item { float: left; padding-right: 32px; } --> </style> </head> <body> <div id="outerDIV" class="myContainer" style="display: block; width: 425px;"> <div id="innerDIV"> <div class="item"> --------My test string #1-------- </div> <div class="item"> ------test2------- </div> <div class="item"> test </div> </div> </div> </body> </html>

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  • DataContractJsonSerializer generating Ghost string to JSON keys?

    - by Anil Namde
    DataContractJsonSerializer this is nice class added in the .net framework which can be used to serialize/desirealize object into JSON. Now following is the example i am trying [Serializable] class User { public string name; public string userId; } Now following is the output generated Output : Notice structure where only "name" is expected instead of k__BackingField Now this is the problem after digging so much i am not sure from where < and _BackingField is coming ? { "<name>k__BackingField":"test user", "<userId>k__BackingField":100001}

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  • EJB-like plug-in to VS2008?

    - by Phil
    I'd like to be able to just write a class and get a table generated in my DB along with all the properties of that class. In EJB it's possible to let the container handle the data and "sync" with the DB. I'd like something like this in VS2008 with C# .NET and ASP.NET. Is there anything remotely like this on the market?

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  • How to map LINQ EntitySet to List property in property setter?

    - by jlp
    In my model I have these entities: public interface IOrder { string Name {get;set;} List<IProduct> OrderedProducts {get;set;} } public interface IProduct {} In partial class generated by linq-to-sql I map these properties on my entity properties: public partial class Order : IOrder { List<IProduct> OrderedProducts { get { return this.L2SQLProducts.Cast<IProduct>.ToList(); } set { this.L2SQLProducts = ??? } } } How should setter look like?

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  • adding a property to an EventArgs

    - by aleroot
    I have extended the standard FileSystemWatcher class by adding a string property (fileToTest), now i need to extend also the FileSystemEventArgs to add this property how can i do this ? my extend FileSystemWatcher : class AleFileSystemWatcher : FileSystemWatcher { public string fileToTest { get; set; } } The FileSystemEventArgs fileToTest property should be the same of AleFileSystemWatcher fileToTest . Can i do this ?

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  • jQuery: How to reset all element positions on page?

    - by Rudi
    Hey everyone. Let's say I have a bunch of DIVs with a class of "apple", and another bunch of DIVs with a lass of "orange". All these DIVs have various positions, but I want to use a jQuery function to assign them new positions relative to their parent containers live on the page without any reloading. So, for example, how do I set all DIVs with the class of "apple" to a "top" value of "200px" relative to the parent container without reloading the page? Thanks!

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  • Html Agility Pack: Setting an HtmlNode's Attribute Value isn't reflected in the HtmlDocument.

    - by Avi
    In Html Agility Pack, when I set an attribute of an HtmlNode, should I see this in the HtmlDocument from which the node was selected? Lets say that htmlDocument is an HtmlDocument. So the simplified code looks like this: HtmlNode documentNode = htmlDocument.DocumentNode; HtmlNodeCollection nodeCollection = documentNode.SelectNodes(someXPath); foreach(var node in nodeCollection) if(SomeCondition(node)) node.SetAttributeValue("class","something"); Now, I see the class attribte of node change, but I don't see this change reflected in the htmlDocument's html.

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  • Re-define File::dirname ruby method

    - by jrhicks
    I'm trying to redefine the File.dirname method to first change %20s to spaces. But the following gives me an error class File old_dirname = instance_method(:dirname) define_method(:dirname) { |s| s = s.gsub("%20"," ") old_dirname.bind(self).call(s) } end This trhows a NameError exception: undefined method 'dirname' for class 'File' What is the right way to do this?

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  • Django form and User data

    - by Dean
    I have a model that looks like this: class Client(models.Model): name = models.CharField(max_length=100, primary_key=True) user = models.ForeignKey(User) class Contract(models.Model): title = models.CharField(max_length=100, primary_key=True) start_date = models.DateField() end_date = models.DateField() description = models.TextField() client = models.ForeignKey(Client) user = models.ForeignKey(User) How can i configure a django form so that only clients associated with that user show in the field in the form? My initial thought was this in my forms.py: client = forms.ModelChoiceField(queryset=Client.objects.filter(user__username = User.username)) But it didn't work. So how else would I go about it?

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  • Seg Fault with malloc'd pointers

    - by anon
    I'm making a thread class to use as a wrapper for pthreads. I have a Queue class to use as a queue, but I'm having trouble with it. It seems to allocate and fill the queue struct fine, but when I try to get the data from it, it Seg. faults. http://pastebin.com/Bquqzxt0 (the printf's are for debugging, both throw seg faults) edit: the queue is stored in a dynamically allocated "struct queueset" array as a pointer to the data and an index for the data

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  • Django model help

    - by dotty
    Does anyone have any clue why this doesn't work as expected. If i use the python shell and do team.game_set or team.games It returns an error AttributeError: 'Team' object has no attribute 'game' If i create a Game object and call game.home_team it returns the correct team object Heres my model class Team(models.Model): name = models.CharField(blank=True, max_length=100) class Game(models.Model): home_team = models.ForeignKey(Team, related_name="home_team")

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