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• C# compile finalize method's on runtime?

  - by Royi Namir

  As im reading through 3 books about GC , ive notice some strange fact : C# via CLR CriticalFinalizerObject : the CLR treats this class and classes derived from it in a very special manner what ??? "not find enough memory to COMPILE a method? " IMHO - the code should be already compiled... no ? when Im writing c# code - the whole code is compiled to IL before its running... no? but according to the text - at RUNTIME - he MAY find insufficient memory for compile... Help ?

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• What really is the purpose of "base" keyword in c#?

  - by Pandiya Chendur

  Thus for used base class for some commom reusable methods in every page of my application... public class BaseClass:System.Web.UI.Page { public string GetRandomPasswordUsingGUID(int length) { string guidResult = System.Guid.NewGuid().ToString(); guidResult = guidResult.Replace("-", string.Empty); return guidResult.Substring(0, length); } } So if i want to use this method i would just do, public partial class forms_age_group : BaseClass { protected void Page_Load(object sender, EventArgs e) { //i would just call it like this string pass = GetRandomPasswordUsingGUID(10); } } It does what i want but there is a "Base" keyword that deals with base class in c# ... I really want to know when should use base keyword in my derived class.... Any good example...

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• Creating ostream manipulators for a specific class

  - by petersohn

  I have a class that is derived from ostream: class my_ostream: public std::ostream { // ... } I want to make a manipulator (for example do_something), that works specifically to this class, like this: my_ostream s; s << "some text" << do_something << "some more text"; I did the following: std::ostream &do_something(std::ostream &os) { my_ostream *s = dynamic_cast<my_ostream*>(&os); if (s != NULL) { // do something } return os; } This works, but is rather ugly. I tried the following: my_ostream &do_something(my_ostream &s) { // do something return s; } This doesn't work. I also tried another approach: class my_ostream: public std::ostream { // ... my_ostream &operator<<(const do_something & x) { // do something return *this; } } This still doesn't work.

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• designing classes and objects in .net for a restaurant assignment

  - by Dell Boy

  I have received an assignment at School for creating a Restaurant site. I have to use objects and classes (OOP) for my assignment. I have the foundations of the OOP in .net, but what I don't know is how can I design this assignment to be object-oriented. I don't know how to start it. The requirement is like this: The menu has to be saved in a database and retrieved from it. The menu is devided in appetizers, Salades, Main Meal, Pastas, Wines, Beverages, Extras, Do I create classes like this: Base Class: Menu Derived classes: Appetizers, Salades, Main meal, Pastas, wines, etc. If you have a good example about how to create classes from a Menu that will be great. You don't have to rely on the example I gave above. The menu can be anything. I can deside what the menu will contain. thanks a lot. I am waiting for some help. Please

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• Scala case class generated field value

  - by Petteri Hietavirta

  I have an existing Scala application and it uses case classes which are then persisted in MongoDB. I need to introduce a new field to a case class but the value of it is derived from existing field. For example, there is phone number and I want to add normalised phone number while keeping the original phone number. I'll update the existing records in MongoDB but I would need to add this normalisation feature to existing save and update code. So, is there any nice shortcut in Scala to add a "hook" to a certain field of a case class? For example, in Java one could modify setter of the phone number.

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• Updating Many-to-Many relationship with LinqToSQL

  - by Noffie

  If I had, for example, a Many-to-Many mapping table called "RolesToUsers" between a Users and an Roles table, here is how I do it: // DataContext is db, usr is a User entity // newUserRolesMappings is a collection with the desired new mappings, probably // derived by looking at selections in a checkbox list of Roles on a User Edit page db.RolesToUsers.DeleteAllOnSubmit(usr.RolesToUsers); usr.RolesToUsers.Clear(); usr.RolesToUsers.AddRange(newUserRolesMappings); I used the SQL profiler once, and this seems to generate very intelligent SQL - it will only drop the rows which are no longer in the mapping relationship, and only add rows which did not already exist in the relationship. It doesn't blindly do a complete clearing and re-construction of the relationship, as I thought it would. The internet is surprisingly quiet on the subject, and the query "LinqToSQL many-to-many" mostly just turns up articles about how the LinqToSQL data mapper doesn't "support" it very well. How does everyone else update many-to-many with LinqToSQL?

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• Can I use a stream to INSERT or UPDATE a row in SQL Server (C#)?

  - by Cheeso

  Suppose I have a VarBinary[MAX] column, can I insert or update into that column using a type derived from System.IO.Stream? How? I think that I can obtain a read-only stream from such a column using a SqlDataReader, calling GetSqlBytes() on the reader, getting the SqlBytes instance, and then referencing the Stream property on that. What I want is the converse - I want a stream for update or insert. Possible? (from c#... Without writing T-SQL ?)

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• Communicating between classes set up in nib, in code?

  - by cannyboy

  A beginner's question: If, in your nib, you have the File's Owner linked to the ViewController class, and you also have a NSObject-derived class, how do you communicate between the ViewController class and the NSObject class within code? For instance, suppose ScientificCalculatorView.xib looks like this File's Owner (class: ScientificCalculatorViewController) FirstResponder View Calculator (an object that has been linked to the Calculator class) Obviously, I'd want Calculator to be reusable, so it could be used with a NormalCalculatorViewController or something like that. So that UI and the calculator code are separate. Does Calculator even need to be in the nib? It's a beginners question, but I'm just trying to get my head around it.

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• Constructor with non-instance variable assistant?

  - by Robert Fischer

  I have a number of classes that look like this: class Foo(val:BasicData) extends Bar(val) { val helper = new Helper(val) val derived1 = helper.getDerived1Value() val derived2 = helper.getDerived2Value() } ...except that I don't want to hold onto an instance of "helper" beyond the end of the constructor. In Java, I'd do something like this: public class Foo { final Derived derived1, derived2; public Foo(BasicData val) { Helper helper = new Helper(val); derived1 = helper.getDerived1Value(); derived2 = helper.getDerived2Value(); } } So how do I do something like that in Scala? I'm aware of creating a helper object of the same name of the class with an apply method: I was hoping for something slightly more succinct.

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• Generic Abstract Singleton with Custom Constructor in C#

  - by Heka

  I want to write a generic singleton with an external constructor. In other words the constructor can be modified. I have 2 designs in my mind but I don't know whether they are practical or not. First one is to enforce derived class' constructor to be non-public but I do not know if there is a way of it? Second one is to use a delegate and call it inside the constructor? It isn't necessarily to be a constructor. The reason I chose custom constructor is doing some custom initializations. Any suggestions would be appreciated :)

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• Jquery convert integer to string and back

  - by Richbyte

  These are the logical steps which i need render with jquery: var x is a 2 digit number(integer) derived from an input.value(); If var x is not 33 or 44 Convert this 2 digit number to string; split the string in 2 parts as number; Add these 2 values; Return var x value as this value. Else Return var x value literally as 33 or 44 whatever is the case. Thanks!

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• Printing complex widgets in Qt

  - by Jens

  I have a complex widget with tons of different subwidgets, e.g. subclasses of QLabel. I want to print this widget, but obviously I do not want to print the background, I want to print with differing text colors or have the style of frames slightly modified. As I do not really want to iterate through all subwidgets with a special "print" function, which I would need to attach to all widgets (how to add "print" to a QLabel?), I would like to use paintEvent. If I have a hierarchy MyWidget - derived from - some QWidget, I would like to insert a sublayer MyWidget - MyPrintWidget - some QWidget, where myPrintWidget::paintEvent would check, if the current print is going to the screen (thus call QWidget::paintEvent), else if we are printing to the printer, call some function MyPrintWidget::drawWidget instead. Is this the right way to print-enable a widget? How can I figure out in paintEvent, that I'm printing to a printer instead of the screen? Is there a good example of printing complex widgets?

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• What is this Design Pattern?

  - by Can't Tell

  I read the Wikipedia articles on FactoryMethod and AbstractFactory but the following code doesn't seem to fit anywhere. Can someone explain to me what the following pattern is or if it is an anti-pattern? interace PaymentGateway{ void makePayment(); } class PaypalPaymentGateway implements PaymentGateway { public void makePayment() { //some implementation } } class AuthorizeNetPaymentGateway implements PaymentGateway { public void makePayment() { //some implementation } } class PaymentGatewayFacotry{ PaymentGateway createPaymentGateway(int gatewayId) { if(gatewayId == 1) return PaypalPaymentGateway(); else if(gatewayId == 2) return AuthorizeNetPaymentGateway(); } } Let's say the user selects the payment method using a radio button on an html page and the gatewayId is derived from the radio button value. I have seen code like this and thought it was the AbstractFactory pattern but after reading the Wikipedia article, I'm having doubts.

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• How to extend abstract Entity class in RIA Services

  - by Calanus

  I want to add a bool variable and property to the base Entity class in my RIA services project so that it is available throughout all the entity objects but seem unable to work out how to do this. I know that adding properties to actual entities themselves is easy using .shared.cs and partial classes but adding such properties to the Entity class using similar methods doesn't work. For example, the following code doesn't work namespace System.ServiceModel.DomainServices.Client { public abstract partial class Entity { private bool auditRequired; public bool AuditRequired { get { return auditRequired; } set { auditRequired = value; } } } } All that happens is that the existing Entity class gets totally overriden rather than extending the Entity class. How do I extend the base Entity class so that functionality is available thoughout all derived entity classes?

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• How to change default font in netbeans platform?

  - by nathan

  I'd like to know how to change the default font used in netbeans platform. I'm not asking for changing the font in the Netbeans IDE but in the platform, then all my derived applications would use this default font. A netbeans application is a group of Jcomponent so i could easily set the font of each of those components but there is still things like notifications that i can't access directly to change the font, so i think the best would be to change the font by default. Programmaticaly or any other way... maybe editing one the jar?

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• Sad logic on types

  - by user2972231

  Code base is littered with code like this: BaseRecord record = // some BaseRecord switch(record.source()) { case FOO: return process((FooRecord)record); case BAR: return process((BarRecord)record); case QUUX: return process((QuuxRecord)record); . . // ~25 more cases . } and then private SomeClass process(BarRecord record) { } private SomeClass process(FooRecord record) { } private SomeClass process(QuuxRecord record) { } It makes me terribly sad. Then, every time a new class is derived from BaseRecord, we have to chase all over our code base updating these case statements and adding new process methods. This kind of logic is repeated everywhere, I think too many to add a method for each and override in the classes. How can I improve this?

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• How to get a component's parent form in Borland VCL?

  - by nklein

  Hi, I'd like to determine which form a given component belongs to in my application. Neither the Parent nor the Owner property can be assumed to be the form itself, so I can't simply use this. I guess I could just go through the Parent property recursively until I arrive at something derived from TForm, but is there a better way to do this? I used the search function, but couldn't find anything specific to my problem. I'm using Borland C++ Builder, by the way (tagged Delphi because a majority of VCL users seem to write in Delphi, and I read Delphi code just fine). Thanks in advance!

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• Is it possible to specify a return type of "Derivative(of T)" for a MustOverride sub in VB.NET?

  - by Casey

  VB.NET 2008 .NET 3.5 I have two base classes that are MustInherit (partial). Let's call one class OrderBase and the other OrderItemBase. A specific type of order and order item would inherit from these classes. Let's call these WebOrder (inherits from OrderBase) and WebOrderItem (inherits from OrderItemBase). Now, in the grand scheme of things WebOrder is a composite class containing a WebOrderItem, like so: Public Class WebOrder Inherits OrderBase Public Property OrderItem() as WebOrderItem End Property End Class Public Class WebOrderItem Inherits OrderItemBase End Class In order to make sure any class that derives from OrderBase has the OrderItem property, I would like to do something like this in the OrderBase class: Public MustInherit Class OrderBase Public MustOverride Property OrderItem() as Derivative(Of OrderItemBase) End Class In other words, I want the derived class to be forced to contain a property that returns a derivative of OrderItemBase. Is this possible, or should I be using an entirely different approach?

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• Dynamic binding in C++

  - by chmike

  I'm implementing a CORBA like server. Each class has remotely callable methods and a dispatch method with two possible input, a string identifying the method or an integer which would be the index of the method in a table. A mapping of the string to the corresponding integer would be implemented by a map. The caller would send the string on the first call and get back the integer with the response so that it simply has to send the integer on subsequent calls. It is just a small optimization. The integer may be assigned dynamically on demand by the server object. The server class may be derived from another class with overridden virtual methods. What could be a simple and general way to define the method binding and the dispatch method ?

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• LINQ - group specific types of classes

  - by Nelson

  This question is similar to http://stackoverflow.com/questions/2835192/linq-group-one-type-of-item but handled in a more generic way. I have a List that has various derived classes. I may have something like this: List<BaseClass> list = new List<BaseClass>() { new Class1(1), new Class2(1), new Class1(2), new Class3(1), new Class2(2), new Class4(1), new Class3(2) }; I am trying to use LINQ to semi-sort the list so that the natural order is maintained EXCEPT for certain classes which have base.GroupThisType == true. All classes with GroupThisType should be grouped together at the place that the first class of the same type occurs. Here is what the output should be like: List<BaseClass> list = new List<BaseClass>() { new Class1(1), new Class1(2), new Class2(1), new Class3(1), new Class3(2) new Class2(2), new Class4(1), };

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• Questions about "casting operation" in OOP

  - by rhapsodyn

  When programming, we usually use some type-casting operations. When the casting happens on the objects "on the same level", it feels ok. But when it happens on the ojects "on the different levels"(mainly between father and son), it feels weird. Considering this: Class Son extends Father WhenSon s = (Son)father;, it's absolutely unreasonable. Because a "Son" is not a "Father" anymore, "Son" may grow up with some new properties "Father" doesn't have, the casting operation makes these properties unknown. On the other hand, Father f = (Father)son seems reasonable, but according to LSP "An instance of a derived should be able to replace any instance of its superclass" A "Son" can do anything his "Father" can, so the casting operation seems useless. So can i say that these casting operations are agaisnt OO design principle but necessary?

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• Solution for distributing MANY simple network tasks?

  - by EmpireJones

  I would like to create some sort of a distributed setup for running a ton of small/simple REST web queries in a production environment. For each 5-10 related queries which are executed from a node, I will generate a very small amount of derived data, which will need to be stored in a standard relational database (such as PostgreSQL). What platforms are built for this type of problem set? The nature, data sizes, and quantities seem to contradict the mindset of Hadoop. There are also more grid based architectures such as Condor and Sun Grid Engine, which I have seen mentioned. I'm not sure if these platforms have any recovery from errors though (checking if a job succeeds). What I would really like is a FIFO type queue that I could add jobs to, with the end result of my database getting updated. Any suggestions on the best tool for the job?

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• non-scalar type requested

  - by lego69

  can somebody please help me with an error conversion from `A' to non-scalar type `B' requested I have class A and derived from it B, but I have problems with these rows: A a(1); A *pb = new B(a); B b = *pb; //here I have an error thanks in advance for any help class A { protected: int player; public: A(int initPlayer = 0); A(const A&); A& operator=(const A&); virtual ~A(){}; virtual void foo(); void foo() const; operator int(); }; class B: public A { public: B(int initPlayer): A(initPlayer){}; ~B(){}; virtual void foo(); };

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• Converting BindingList(Of T) to Array

  - by George

  Public Class Orders Inherits System.ComponentModel.BindingList(Of Order) End Class Public Sub DataBind(ByVal Orders() As Orders) End Sub Dim MyOrders() As Order = Orders.ToArray SuperListBinder.DataBind(MyOrders) '<<Error occurs on this line I don't understand this error. I think that I am passing the appropriate data type to a sub. I don't understand the meaning of "Cannot convert object of type x to an object of type x! Note that, if relevant, my Solution File contains ,multiple projects and that they are all project references. Error: Error 1 Value of type '1-dimensional array of BESI.BusinessObjects.Order' cannot be converted to '1-dimensional array of BESI.BusinessObjects.Orders' because 'BESI.BusinessObjects.Order' is not derived from 'BESI.BusinessObjects.Orders'. C:\My\Code\BESI\BesiAdmin\Forms\Activity.vb 17 34 BesiAdmin

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• C++ Typing and OOP child classes

  - by Zack

  I'm a bit confused: If I have a base class A, and a class B which extends A, can a variable of the type A hold a value of the type B and vice versa? If yes, why? Aren't they completely different even if B is derived from A? How about type-safety? If this is possible, what things do I have to mind when taking use of this? How would this work out in terms of performance? Note: Sorry if I asked too many questions, just ignore them and just look out for those "marked" with the list decoration dot :) Also, this is not my homework. I'm a hobby programmer and have skills in scripting languages with OOP, yet I'm relatively new to OOP typing in C++.

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