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• What is a good practice for handling SQL connections within a WCF call?

  - by Rising Star

  Suppose I want to create a (stateless) WCF service with three methods exposed on an endpoint: performSqlOperationA(), performSqlOperationB(), and performSqlOperationC(). Each method inserts data into a SQL database. The way I've seen things done at my office, each method would begin with code to initialize a SqlConnection object. Each method would end with code to safely dispose it. What is a good practice for coding these WCF methods so that the SqlConnection object is initialized and disposed in each method without having to do these things in each method? I know that I can have the connection initialized in the constructor for the class for the WCF methods, but I don't know about disposing it... The calls cannot be wrapped in a using block. One solution I'm familiar with is PostSharp, which allows me to set an attribute which causes specific code to automatically run at the beginning and end of each method call, but it would be greatly preferable to do this with only the .net framework.

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• Castle Windsor Weak Typed Factory

  - by JeffN825

  In a very very limited number of scenarios, I need to go from an unknown Type (at compile time) to an instance of the object registered for that type. For the most part, I use typed factories and I know the type I want to resolve at compile time...so I inject a Func<IMyType> into a constructor ...but in these limited number of scenarios, in order to avoid a direct call to the container (and thus having to reference Windsor from the library, which is an anti-pattern I'd like to avoid), I need to inject a Func<Type,object>...which I want to internally container.Resolve(type) for the Type parameter of the Func. Does anyone have some suggestions on the easiest/most straightforward way of setting this up? I tried the following, but with this setup, I end up bypassing the regular TypedFactoryFacility altogether which is definitely not what I want: Kernel.Register(Component.For(typeof (Func<Type, object>)).LifeStyle.Singleton.UsingFactoryMethod( (kernel, componentModel, creationContext) => kernel.Resolve(/* not sure what to put here... */))); Thanks in advance for any assistance.

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• Java - Thread safety of ArrayList constructors

  - by andy boot

  I am looking at this piece of code. This constructor delegates to the native method "System.arraycopy" Is it Thread safe? And by that I mean can it ever throw a ConcurrentModificationException? public Collection<Object> getConnections(Collection<Object> someCollection) { return new ArrayList<Object>(someCollection); } Does it make any difference if the collection being copied is ThreadSafe eg a CopyOnWriteArrayList? public Collection<Object> getConnections(CopyOnWriteArrayList<Object> someCollection) { return new ArrayList<Object>(someCollection); }

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• Pattern matching for lambda expressions

  - by alphomega

  21 --Primitive recursion constructor 22 pr :: ([Int] -> Int) -> ([Int] -> Int) -> ([Int] -> Int) 23 pr f g = \xs 0 -> f xs 24 pr f g = \xs (y+1) -> g xs y ((pr f g) xs y) I want the function this function creates to act differently on different inputs, so that it can create a recursive function. As expected, the above code doesn't work. How do I do something like pattern matching, but for the function it creates? Thanks

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• Extended slice that goes to beginning of sequence with negative stride

  - by recursive

  Bear with me while I explain my question. Skip down to the bold heading if you already understand extended slice list indexing. In python, you can index lists using slice notation. Here's an example: >>> A = list(range(10)) >>> A[0:5] [0, 1, 2, 3, 4] You can also include a stride, which acts like a "step": >>> A[0:5:2] [0, 2, 4] The stride is also allowed to be negative, meaning the elements are retrieved in reverse order: >>> A[5:0:-1] [5, 4, 3, 2, 1] But wait! I wanted to see [4, 3, 2, 1, 0]. Oh, I see, I need to decrement the start and end indices: >>> A[4:-1:-1] [] What happened? It's interpreting -1 as being at the end of the array, not the beginning. I know you can achieve this as follows: >>> A[4::-1] [4, 3, 2, 1, 0] But you can't use this in all cases. For example, in a method that's been passed indices. My question is: Is there any good pythonic way of using extended slices with negative strides and explicit start and end indices that include the first element of a sequence? This is what I've come up with so far, but it seems unsatisfying. >>> A[0:5][::-1] [4, 3, 2, 1, 0]

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• Generics and reflection in Java

  - by Ragesh

  This is probably a very basic question, but I'm really new to generics in Java and I'm having a hard time altering my thought process from the way things are done in C#, so bear with me. I'm trying to build a generic repository in Java. I've created an IRepository interface that looks like this: public interface IRepository<T extends IEntity> And a Repository class that looks like this: public class Repository<T extends IEntity> implements IRepository<T> Now, from within the constructor of my Repository class, I'd like to be able to "divine" the exact type of T. For example, if I instantiated a repository like this: IRepository<MyClass> repo = new Repository<MyClass>(); I'd like to know that T is actually MyClass. This is trivial in C#, but obviously generics are a totally different beast in Java and I can't seem to find anything that would help me do this.

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• silverlight adding single prism command delegate to a list of items in xaml

  - by bobwah

  I'm building a menu using Prism (using a trtelerik tree view with hierarchy data templates but hopefully the details don't matter) and I'm trying to set up a Click.Command on each menu items bindings that will all call the same delegate command which is defined in the view model. The menu is built up out of items which I don't really want to put any references to the command in. How do I bind the command to each of these items in xaml? I've looked around and it looks like in WPF I could use a relative source binding and find ancestors but there doesn't seem to be a way of doing this in silverlight. Can I setup the delegate as a static resource somehow? I don't think I can create a static resource to the view model as this uses Unity to resolve paramters to it's constructor.

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• Create a class with array of objects.

  - by Bi

  Hi Code below defines a ChargeCustomer class that contains an array of type "customers". I want to be able to create an object with either 1 "customer" or 2 "customers" based on the constructor parameters. Is this the right way to do so in C#: public class ChargeCustomer { private Customer[] customers; public ChargeCustomer( string aName, string bName, int charge ) { customers = new Customer[2]; customers[0] = new Customer(aName, charge); customers[1] = new DropBox(bName, charge); } public ChargeCustomer( string bName, int charge ) { customers = new Customer[1]; customers[0] = new Customer( bName, charge ); } } Thanks!

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• php class basic question

  - by Ross

  hi <?php class myClass { var $input; var $output; function myClass($input) { $output = 'You entered: ' . $input; return $output; } } $test = new myClass; echo $test->myClass(123); ?> this works, but returns this warning: Warning: Missing argument 1 for myClass::myClass() I read in to this, and seems that the constructor is expecting a value, so by adding: function myClass($input='') the warning is removed, but this seems so unnecessary? could someone enlighten me as to why it's required to define a value to prevent that warning? thanks for any pointers

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• how to get TabHeader on trigger

  - by CurlyFro

  i have a tabcontrol. i'm trying to pass the tabcontrol as a parameter to figure out the selected tab item so i can get the tab header name. Binding this doesn't seem to work. ideas? <TabControl Background="#FFF9F9F9" Height="650"> <i:Interaction.Triggers> <i:EventTrigger EventName="SelectionChanged"> <n:ExecuteCommandAction Command="{Binding UpdateTabCommand}" Parameter="{Binding this}"/> </i:EventTrigger> </i:Interaction.Triggers> in my viewmodel constructor i have: _updateTabCommand = new ActionCommand< TabControl>(UpdateTab); private method: public void UpdateTab(TabControl tabControl) { var tabItem = (TabItem)tabControl.SelectedItem;

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• Hidden Features of Google Guice

  - by Jon

  Google Guice provides some great dependency injection features. I came across the @Nullable feature recently which allows you to mark constructor arguments as optional (permitting null) since Guice does not permit these by default: e.g. public Person(String firstName, String lastName, @Nullable Phone phone) { this.firstName = checkNotNull(firstName, "firstName"); this.lastName = checkNotNull(lastName, "lastName"); this.phone = phone; } http://code.google.com/p/google-guice/wiki/UseNullable What are the other useful features of Guice (particularly the less obvious ones) that people use?

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• Want to understand C++ sentry object

  - by Romain Hippeau

  I answered this [question][1] and somebody else had answered as he modern C++ equivalent would be a sentry object: construct it at the beginning of a function, with its constructor implementing call(), and upon return (or abnormal exit), its destructor implements I am not familiar with using sentry objects in C++. I thought they were limited to input and output streams. Could somebody explain to me about C++ sentry objects as well as how to use them as an around interceptor for one or more methods in a class ? [1]: http://stackoverflow.com/questions/2688043/call-return-feature-of-classic-cc-with-classes-what-modern-languages-have-it/2688095#2688095 /

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• File mkdirs() method not working in android/java

  - by Leif Andersen

  I've been pulling out my hair on this for a while now. The following method is supposed to download a file, and save it to the location specified on the hard drive. private static void saveImage(Context context, boolean backgroundUpdate, URL url, File file) { if (!Tools.checkNetworkState(context, backgroundUpdate)) return; // Get the image try { // Make the file file.getParentFile().mkdirs(); // Set up the connection URLConnection uCon = url.openConnection(); InputStream is = uCon.getInputStream(); BufferedInputStream bis = new BufferedInputStream(is); // Download the data ByteArrayBuffer baf = new ByteArrayBuffer(50); int current = 0; while ((current = bis.read()) != -1) { baf.append((byte) current); } // Write the bits to the file OutputStream os = new FileOutputStream(file); os.write(baf.toByteArray()); os.close(); } catch (Exception e) { // Any exception is probably a newtork faiilure, bail return; } } Also, if the file doesn't exist, it is supposed to make the directory for the file. (And if there is another file already in that spot, it should just not do anything). However, for some reason, the mkdirs() method never makes the directory. I've tried everything from explicit parentheses, to explicitly making the parent file class, and nothing seems to work. I'm fairly certain that the drive is writable, as it's only called after that has already been determined, also that is true after running through it while debugging. So the method fails because the parent directories aren't made. Can anyone tell me if there is anything wrong with the way I'm calling it? Also, if it helps, here is the source for the file I'm calling it in: https://github.com/LeifAndersen/NetCatch/blob/master/src/net/leifandersen/mobile/android/netcatch/services/RSSService.java Thank you

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• Objective C instance variables - Newbie

  - by Dwayne King

  OK - so I'm sure my confusion here is just a result of being stuck in a "Java mindset" and not understanding how Obj C differs in this case. In Java, I can declare a variable in a class, like this, and each instance of that class will have it's own: MyClass { String myVar; MyClass() { // constructor } } In Obj C I tried to do the same thing by declaring a variable only in the .m file like this: #import "MyClass.h" @implementation MyClass NSString *testVar; @end My expectation here was that this variable has a scope limited to this class. So I created a second class (identical): #import "MySecondClass.h" @implementation MySecondClass NSString *testVar; @end What I'm seeing (and has me baffled) is that changing the variable in one class, affects the value seen in the other class. In fact, if I set a breakpoint, and then "Jump to Definition" of the variable, it takes me to th I've created an extremely small XCode project that demonstrates the problem here Nothing more humbling than moving to a new language :) Thanks in advance.

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• Usage patterns/use cases for DI or when to start using it

  - by Fabian

  I'm not sure for which use cases one should to use DI in the application. I know that injecting services like PlaceService or CalculationService etc fits very well but should I also create my domain objects with DI like a User? What is if the User has only one constructor which requires a first and lastname. Is this solveable with DI? Should I use DI to create the instances for Set/List interfaces or is this pure overkill? I use guice primarily.

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• Opinions about Dabo

  - by driverate

  Has anyone used Dabo lately? How does it rate vs Boa Constructor, etc? I'm writing a new Python database app and Dabo looks promising, but what's the real-world scoop on it? Is it used by many developers? It's not talked about very much here on SO, or anywhere, as far as I can tell. I'm just a little concerned that the support community might be too small, or the possibility that writers might decide to throw in the towel. What is your assessment of Dabo?

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• How to initialise an array inside a struct without doing each element separately? (C++)

  - by Janet

  My questions are in the code, but basically i want to know how/if I can do the two commented out lines? I know I can do it in a constructor but I don't want to! struct foo { int b[4]; } boo; //boo.b[] = {7, 6, 5, 4}; // <- why doesn't this work? (syntax error : ']') //boo.b = {7, 6, 5, 4}; // <- or else this? (syntax error : '{') boo.b[0] = 7; // <- doing it this way is annoying boo.b[1] = 6; // : boo.b[2] = 5; // : boo.b[3] = 4; // <- doing it this way is annoying boo.b[4] = 3; // <- why does this work! (Using: C++, Visual Studio 2005.)

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• Can I use Linq to project a new typed datarow?

  - by itchi

  I currently have a csv file that I'm parsing with an example from here: http://alexreg.wordpress.com/2009/05/03/strongly-typed-csv-reader-in-c/ I then want to loop the records and insert them using a typed dataset xsd to an Oracle database. It's not that difficult, something like: foreach (var csvItem in csvfile) { DataSet.MYTABLEDataTable DT = new DataSet.MYTABLEDataTable(); DataSet.MYTABLERow row = DT.NewMYTABLERow(); row.FIELD1 = csvItem.FIELD1; row.FIELD2 = csvItem.FIELD2; } I was wondering how I would do something with LINQ projection: var test = from csvItem in csvfile select new MYTABLERow { FIELD1 = csvItem.FIELD1, FIELD2 = csvItem.FIELD2 } But I don't think I can create datarows like this without the use of a rowbuilder, or maybe a better constructor for the datarow?

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• Declaring an enum within a class

  - by bporter

  In the following code snippet, the Color enum is declared within the Car class in order to limit the scope of the enum and to try not to "pollute" the global namespace. class Car { public: enum Color { RED, BLUE, WHITE }; void SetColor( Car::Color color ) { _color = color; } Car::Color GetColor() const { return _color; } private: Car::Color _color; }; (1) Is this a good way to limit the scope of the Color enum? Or, should I declare it outside of the Car class, but possibly within its own namespace or struct? I just came across this article today, which advocates the latter and discusses some nice points about enums: http://gamesfromwithin.com/stupid-c-tricks-2-better-enums. (2) In this example, when working within the class, is it best to code the enum as Car::Color, or would just Color suffice? (I assume the former is better, just in case there is another Color enum declared in the global namespace. That way, at least, we are explicit about the enum to we are referring.) Thanks in advance for any input on this.

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• odd url, and difficulty in following the php page flow

  - by sdfor

  I'm trying to understand code that I bought so I can modify it. In the index.php there are picture links: <a href="test10,10"><img title="" border=1 src="makethumb.php?pic=product_images/test101.jpg&amp;w=121&amp;sq=N" / ></a> I don't understand the href since it is not pointing to a page. test10 is an id of a picture. I assumed it was going back to the index.php and the code would extract the test10,10 from the url, but it's not. I know that because I put in trace code as the first line. The question is, where is the link going to? I know it that it somewhere in the process it executes a page called profile.php, but nowhere in the source code (doing a global search) is there an explicit call to profile.php. As a related question, is there a way to profile the code to see what pages it's calling without using xdebug, which for the life of me I can't get working after many hours of trying every suggestion I found here and else where. (I'm using xampp) thanks

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• How to default-initialize local variables of built-in types in C++?

  - by sharptooth

  How do I default-initialize a local variable of primitive type in C++? For example if a have a typedef: typedef unsigned char boolean;//that's Microsoft RPC runtime typedef I'd like to change the following line: boolean variable = 0; //initialize to some value to ensure reproduceable behavior retrieveValue( &variable ); // do actual job into something that would automagically default-initialize the variable - I don't need to assign a specific value to it, but instead I only need it to be intialized to the same value each time the program runs - the same stuff as with a constructor initializer list where I can have: struct Struct { int Value; Struct() : Value() {} }; and the Struct::Value will be default-initialized to the same value every time an instance is cinstructed, but I never write the actual value in the code. How can I get the same behavior for local variables?

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• Mask image does not appear on the screen

  - by Ponty

  I have imported to the library two images and have given them the custom class names MaskImage and MaskedImage. Then i write the code: package { import flash.display.*; public class MaskDemo extends Sprite { // Properties private var sprMaskedImage:Sprite; private var sprMaskImage:Sprite; private var bmMaskedImage:Bitmap; private var bmMaskImage:Bitmap; // Constructor public function MaskDemo() { do_magic(); } // Methods private function do_magic():void { bmMaskedImage = new Bitmap(new MaskedImage(0, 0)); bmMaskImage = new Bitmap(new MaskImage(0, 0)); sprMaskedImage = new Sprite(); sprMaskedImage.addChild(bmMaskedImage); sprMaskImage = new Sprite(); sprMaskImage.addChild(bmMaskImage); sprMaskedImage.mask = sprMaskImage; this.addChild(sprMaskImage); } } } But it does not appear anything on the display. Any ideas why is happening that?

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• Code Analysis Warning CA1004 with generic method

  - by Vaccano

  I have the following generic method: // Load an object from the disk public static T DeserializeObject<T>(String filename) where T : class { XmlSerializer xmlSerializer = new XmlSerializer(typeof(T)); try { TextReader textReader = new StreamReader(filename); var result = (T)xmlSerializer.Deserialize(textReader); textReader.Close(); return result; } catch (FileNotFoundException) { } return null; } When I compile I get the following warning: CA1004 : Microsoft.Design : Consider a design where 'MiscHelpers.DeserializeObject(string)' doesn't require explicit type parameter 'T' in any call to it. I have considered this and I don't know a way to do what it requests with out limiting the types that can be deserialized. I freely admit that I might be missing an easy way to fix this. But if I am not, then is my only recourse to suppress this warning? I have a clean project with no warnings or messages. I would like to keep it that way. I guess I am asking "why this is a warning?" At best this seems like it should be a message. And even that seems a bit much. Either it can or it can't be fixed. If it can't then you are just stuck with the warning with no recourse but suppressing it. Am I wrong?

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• Confusion using MYSQLI

  - by user1020069

  I just started using mysqli API for PHP. Apparently, every time an object of the class MYSQLI is instantiated, it can setup a connection to the database as it connects to the server unlike mysql_connect, which connects to the server first and then you are required to specify the database to query. Now this is a good problem if the db exists, in my case, the db does not exist on the first ever connection to the server/execution of the problem, hence I must connect without specifying the database, which is fine, since the msyqli constructor does not make this database mandatory. My challenge is essentially, how do I check if the database exists before attempting the first connection. The only way to really do this would be to establish a conection to the server and then use the result of the following query to gauge if the database exists: SELECT COUNT(*) AS `exists` FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMATA.SCHEMA_NAME="dbname" ; If this returns true, then the database exists, but now the challenge is how do I get the mysqli object to query this database rather than having to prefix the name of the database in the query. Thanks much

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• Getting list of fields back from 'use fields' pragma?

  - by makenai

  So I'm familiar with the use fields pragma in Perl that can be used to restrict the fields that are stored in a class: package Fruit; use fields qw( color shape taste ); sub new { my ( $class, $params ) = @_; my $self = fields::new( $class ) unless ref $class; foreach my $name ( keys %$params ) { $self->{ $name } = $params->{ $name }; } return $self; } My question is.. once I've declared the fields at the top, how I can get the list back.. say because I want to generate accessors dynamically? Is keys %FIELDS the only way? Secondarily, is there a more efficient way to pre-populate the fields in the constructor than looping through and assigning each parameter as I am above? Thanks!

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