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  • Access to an inner type

    - by sohum
    A colleague of mine posted a question on an internal forum which got me thinking about whether this was possible through C#. Basically, he's got an interface as follows: public interface IProvider<T> { T GetT(); } Is it possible to use something that implements that interface as a type parameter to another generic class and have access to the type T without re-specifying it? For example: public class Foo<P> where P : IProvider<T> { P p; T GetInnerT() { return p.GetT(); } } This does not compile, because the type T is not defined and hence can't be used as a parameter for IProvider. Is something like this even possible? Just curious!

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  • Bound a treeview control to user-defined complex type using EF 4

    - by GIbboK
    Hi, I use Asp.net, SQL 2008 and EF 4. I need display hierarchy data in a treeview control, Data is stored in a DB that use HierarchyId. Unfortunately, EF4 doesn't support HierarchyId. So in this case, I thought to have a stored procedure that deals with my hierarchy and return a result set back to EF that EF4 can turn into a collection of user-defined complex type that can then be bound directly to the treeview control. I imported a SPROC in EF 4 using Import Function and now I have a Complex DataType called: CategoryHierarchy_Result An image of my Model: Here some data from the Complex Type (in a GridView for example GridView1.DataSource = context.CategoryHierarchy(1);): My questions is: How to display my data from my Complex Type in a TreeView Control, showing a Tree structure that respect CategoryNodeString? I am a beginner an I never use TreeView before, any help or resource would be appreciated! Thanks!. Here some useful resource: http://www.robbagby.com/entity-framework/entity-framework-modeling-action-stored-procedures/

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  • .NET Conditional Callback on a type.

    - by Mahesh
    I have a stock price which changes by nature all the time. And, there will be many users who wants to buy that stock. Let's say that the stock price is started at 10 and let's say, 30 people bid for 10.98, 20 people bid for 7.45, 100 people bid for 8.99. During the day, the stock price can touch any of these values, and if that happens, I want to execute all the orders for users who quoted that price. Technically, I am storing in a List. Whenever the price changes, I am checking against all the values in the list and executing those that satisfy the quoted price. Class Bids { string stockname; double quote; } Is there any better alternative way to callback the satisfied items in the list rather than checking all the items whenever there is a change?? If storing in a list is not right way of doing it, let me know the best way.

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  • What's a reasonable way to mutate a primitive variable from an anonymous Java class?

    - by Steve
    I would like to write the following code: boolean found = false; search(new SearchCallback() { @Override void onFound(Object o) { found = true; } }); Obviously this is not allowed, since found needs to be final. I can't make found a member field for thread-safety reasons. What is the best alternative? One workaround is to define final class MutableReference<T> { private T value; MutableReference(T value) { this.value = value; } T get() { return value; } void set(T value) { this.value = value; } } but this ends up taking a lot of space when formatted properly, and I'd rather not reinvent the wheel if at all possible. I could use a List<Boolean> with a single element (either mutating that element, or else emptying the list) or even a Boolean[1]. But everything seems to smell funny, since none of the options are being used as they were intended. What is a reasonable way to do this?

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  • c# Reflection - Find the Generic Type of a Collection

    - by Andy Clarke
    Hi, I'm reflecting a property 'Blah' its Type is ICollection public ICollection<string> Blah { get; set; } private void button1_Click(object sender, RoutedEventArgs e) { var pi = GetType().GetProperty("Blah"); MessageBox.Show(pi.PropertyType.ToString()); } This gives me (as you'd expect!) ICollection<string> ... But really I want to get the collection type i.e. ICollection (rather than ICollection<string>) - does anyone know how i'd do this please?

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  • How to change a variable type in C#?

    - by Mosho Mulan
    I wanted to use something like this: if(x==5) { var mydb= ........ ; } else { var mydb = ........ ; } but it didn't work because I can't declare a variable inside if statement. So I tried to do this: var mydb; if (x==5) { mydb= ............. ; } else { mydb=.............; } but id didn't work either because I had to initialize the variable (mydb). So the question is: I don't necessarily know the type of the variable, can I declare it anyway and then change the type inside the if statement?

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  • Assigning a variable of a struct that contains an instance of a class to another variable

    - by xport
    In my understanding, assigning a variable of a struct to another variable of the same type will make a copy. But this rule seems broken as shown on the following figure. Could you explain why this happened? using System; namespace ReferenceInValue { class Inner { public int data; public Inner(int data) { this.data = data; } } struct Outer { public Inner inner; public Outer(int data) { this.inner = new Inner(data); } } class Program { static void Main(string[] args) { Outer p1 = new Outer(1); Outer p2 = p1; Console.WriteLine("p1:{0}, p2:{1}", p1.inner.data, p2.inner.data); p1.inner.data = 2; Console.WriteLine("p1:{0}, p2:{1}", p1.inner.data, p2.inner.data); p2.inner.data = 3; Console.WriteLine("p1:{0}, p2:{1}", p1.inner.data, p2.inner.data); Console.ReadKey(); } } }

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  • Why do C++ streams use char instead of unsigned char?

    - by Johannes Schaub - litb
    I've always wondered why the C++ Standard library has instantiated basic_[io]stream and all its variants using the char type instead of the unsigned char type. char means (depending on whether it is signed or not) you can have overflow and underflow for operations like get(), which will lead to implementation-defined value of the variables involved. Another example is when you want to output a byte, unformatted, to an ostream using its put function. Any ideas? Note: I'm still not really convinced. So if you know the definitive answer, you can still post it indeed.

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  • Symfony Form render with Self Referenced Entity

    - by benarth
    I have an Entity containing Self-Referenced mapping. class Category { /** * @var integer * * @ORM\Column(name="id", type="integer") * @ORM\Id * @ORM\GeneratedValue(strategy="AUTO") */ private $id; /** * @var string * * @ORM\Column(name="name", type="string", length=100) */ private $name; /** * @ORM\OneToMany(targetEntity="Category", mappedBy="parent") */ private $children; /** * @ORM\ManyToOne(targetEntity="Category", inversedBy="children") * @ORM\JoinColumn(name="parent_id", referencedColumnName="id") */ private $parent; } In my CategoryType I have this : public function buildForm(FormBuilderInterface $builder, array $options) { $plan = $this->plan; $builder->add('name'); $builder->add('parent', 'entity', array( 'class' => 'xxxBundle:Category', 'property' => 'name', 'empty_value' => 'Choose a parent category', 'required' => false, 'query_builder' => function(EntityRepository $er) use ($plan) { return $er->createQueryBuilder('u') ->where('u.plan = :plan') ->setParameter('plan', $plan) ->orderBy('u.id', 'ASC'); }, )); } Actually, when I render the form field Category this is something like Cat1 Cat2 Cat3 Subcat1 Subcat2 Cat4 I would like to know if it's possible and how to display something more like, a kind of a simple tree representation : Cat1 Cat2 Cat3 -- Subcat1 -- Subcat2 Cat4 Regards.

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  • Converting between unsigned and signed int safely

    - by polemic
    I have an interface between a client and a server where a client sends (1) an unsigned value, and (2) a flag which indicates if value is signed/unsigned. Server would then static cast unsigned value to appropriate type. I later found out that this is implementation defined behavior and I've been reading about it but I couldn't seem to find an appropriate solution that's completely safe? I've read about type punning, pointer conversions, and memcpy. Would simply using a union type work? A UnionType containing signed and unsigned int, along with the signed/unsigned flag. For signed values, client sets the signed part of the union, and server reads the signed part. Same for the unsigned part. Or am I completely misunderstanding something? Side question: how do I know the specific behavior in this case for a specific scenario, e.g. windriver diab on PPC? I'm a bit lost on how to find such documentation.

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  • C# 4.0 dynamics

    - by mehanik
    Hi. Code bellow is working well until I have class ClassSameAssembly in same assembly as class Program. But when I move class ClassSameAssembly to separate assembly I have runtime error. Is it posible to resolve it? using System; namespace ConsoleApplication2 { public static class ClassSameAssembly { public static dynamic GetValues() { return new { Name = "Michael", Age = 20 }; } } internal class Program { private static void Main(string[] args) { var d = ClassSameAssembly.GetValues(); Console.WriteLine("{0} is {1} years old", d.Name, d.Age); } } }

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  • C++ Implicit Conversion Operators

    - by Imbue
    I'm trying to find a nice inheritance solution in C++. I have a Rectangle class and a Square class. The Square class can't publicly inherit from Rectangle, because it cannot completely fulfill the rectangle's requirements. For example, a Rectangle can have it's width and height each set separately, and this of course is impossible with a Square. So, my dilemma. Square obviously will share a lot of code with Rectangle; they are quite similar. For examlpe, if I have a function like: bool IsPointInRectangle(const Rectangle& rect); it should work for a square too. In fact, I have a ton of such functions. So in making my Square class, I figured I would use private inheritance with a publicly accessible Rectangle conversion operator. So my square class looks like: class Square : private Rectangle { public: operator const Rectangle&() const; }; However, when I try to pass a Square to the IsPointInRectangle function, my compiler just complains that "Rectangle is an inaccessible base" in that context. I expect it to notice the Rectangle operator and use that instead. Is what I'm trying to do even possible? If this can't work I'm probably going to refactor part of Rectangle into MutableRectangle class. Thanks.

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  • Is there a term for this concept, and does it exist in a static-typed language?

    - by Strilanc
    Recently I started noticing a repetition in some of my code. Of course, once you notice a repetition, it becomes grating. Which is why I'm asking this question. The idea is this: sometimes you write different versions of the same class: a raw version, a locked version, a read-only facade version, etc. These are common things to do to a class, but the translations are highly mechanical. Surround all the methods with lock acquires/releases, etc. In a dynamic language, you could write a function which did this to an instance of a class (eg. iterate over all the functions, replacing them with a version which acquires/releases a lock.). I think a good term for what I mean is 'reflected class'. You create a transformation which takes a class, and returns a modified-in-a-desired-way class. Synchronization is the easiest case, but there are others: make a class immutable [wrap methods so they clone, mutate the clone, and include it in the result], make a class readonly [assuming you can identify mutating methods], make a class appear to work with type A instead of type B, etc. The important part is that, in theory, these transformations make sense at compile-time. Even though an ActorModel<T> has methods which change depending on T, they depend on T in a specific way knowable at compile-time (ActorModel<T> methods would return a future of the original result type). I'm just wondering if this has been implemented in a language, and what it's called.

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  • Returning a local object from a function

    - by pocoa
    Is this the right way to return an object from a function? Car getCar(string model, int year) { Car c(model, year); return c; } void displayCar(Car &car) { cout << car.getModel() << ", " << car.getYear() << endl; } displayCar(getCar("Honda", 1999)); I'm getting an error, "taking address of temporary". Should I use this way: Car &getCar(string model, int year) { Car c(model, year); return c; }

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  • How do I call a function name that is stored in a hash in Perl?

    - by Ether
    I'm sure this is covered in the documentation somewhere but I have been unable to find it... I'm looking for the syntactic sugar that will make it possible to call a method on a class whose name is stored in a hash (as opposed to a simple scalar): use strict; use warnings; package Foo; sub foo { print "in foo()\n" } package main; my %hash = (func => 'foo'); Foo->$hash{func}; If I copy $hash{func} into a scalar variable first, then I can call Foo->$func just fine... but what is missing to enable Foo->$hash{func} to work? (EDIT: I don't mean to do anything special by calling a method on class Foo -- this could just as easily be a blessed object (and in my actual code it is); it was just easier to write up a self-contained example using a class method.) EDIT 2: Just for completeness re the comments below, this is what I'm actually doing (this is in a library of Moose attribute sugar, created with Moose::Exporter): # adds an accessor to a sibling module sub foreignTable { my ($meta, $table, %args) = @_; my $class = 'MyApp::Dir1::Dir2::' . $table; my $dbAccessor = lcfirst $table; eval "require $class" or do { die "Can't load $class: $@" }; $meta->add_attribute( $table, is => 'ro', isa => $class, init_arg => undef, # don't allow in constructor lazy => 1, predicate => 'has_' . $table, default => sub { my $this = shift; $this->debug("in builder for $class"); ### here's the line that uses a hash value as the method name my @args = ($args{primaryKey} => $this->${\$args{primaryKey}}); push @args, ( _dbObject => $this->_dbObject->$dbAccessor ) if $args{fkRelationshipExists}; $this->debug("passing these values to $class -> new: @args"); $class->new(@args); }, ); } I've replaced the marked line above with this: my $pk_accessor = $this->meta->find_attribute_by_name($args{primaryKey})->get_read_method_ref; my @args = ($args{primaryKey} => $this->$pk_accessor); PS. I've just noticed that this same technique (using the Moose meta class to look up the coderef rather than assuming its naming convention) cannot also be used for predicates, as Class::MOP::Attribute does not have a similar get_predicate_method_ref accessor. :(

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  • Most efficient way of checking for a return from a function call in Perl

    - by Gaurav Dadhania
    I want to add the return value from the function call to an array iff something is returned (not by default, i.e. if I have a return statement in the subroutine.) so I'm using unshift @{$errors}, "HashValidator::$vfunction($hashref)"; but this actually adds the string of the function call to the array. I also tried unshift @{$errors}, $temp if defined my $temp = "HashValidator::$vfunction($hashref)"; with the same result. What would a perl one-liner look like that does this efficiently (I know I can do the ugly, multi-line check but I want to learn). Thanks,

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  • why primitive type will call first rather than wrapper classes?

    - by kandarp
    Hello EveryOne, public class A { public void test(Integer i) { System.out.println("In Wrapper Method"); } public void test(int i) { System.out.println("In primitive Method"); } public static void main(String args[]) { A a = new A(); a.test(5); } } When I will call test method from main and pass integer argument, then it will call the method which accept primitive type as argument. I just want to know that why it call primitive type method rather than the method who accepts wrapper class as argument? Is there any rule, which java follow to call methods? Thanks,

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  • How do I add a VSTO project as a reference to a unit testing project?

    - by Mathias
    In order not to pollute my projects with unit tests, I like to create a separate project for my unit tests; I add a reference to the project under test in the unit tests project. However, this isn't working that well with my VSTO excel add-in projects: when I create a separate unit test project and go to Add Reference Projects, there is no project to pick. What I have done so far is Add Reference Browse, and pick the add-in dll from the debug folder. I have also run into issues from time to time with this, with the reference suddenly not working, requiring to remove/re-add the dll reference. Can anybody explain why a VSTO project doesn't show up as a regular project? And is there a better way to go about it than what I am doing presently?

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  • How to add .Net3.5 dll into .Net2.0 project?

    - by macias
    I have a dll which is based on .net 3.5 -- it uses internally for example Linq, but the exposed API is straightforward, no fancy stuff. Since C# generics are resolved at compile time I assume that for calling party all it counts is API (all public parts). However when I try to use this dll from net2.0 project I get info, that the dll cannot be referenced because the dll or one of its dependencies requires a later version of .net framework. I can install any .net version I want on target computer (when entire app is installed), but I cannot change .net version for the project itself. So: how to solve this? When adding a C dll to this project I had no such problems, so are C# dlls self-contained or not?

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