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  • C# Possible to have a generic return type?

    - by JL
    Here is a typical function that returns either true/false; private static bool hasValue() { return true; } Now on an error, I would like to return my own custom error object with definition: public class Failure { public string failureDateTime { get; set; } public string failureReason { get; set; } } I would have expected to be able to throw this custom object for example... private static bool hasValue() { throw new Failure(); } This is not possible, and I don't want to derive Failure from System.IO.Exception because of the inability to serialize an exception in C#. What is the best practice / or ideal solution to this problem. Should I just work with private static object? Or is there a cleaner way to return a custom object or bypass the typical return type on an error (not using System.IO.Exception)? Not entirely wild about object either, because then I need to cast the result and validate it by more boolean logic.

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  • Explicit constructor still has default values even though a default constructor is not invoked.

    - by Phoenix
    According to my understanding a default constructor initializes the state of the object to default values, so if i provide an explicit no-arg public constructor like this then how are the values of d and e still getting initialized to zero because in this case the default constructor is not invoked. public class B extends A{ private int d; private int e; public B() { System.out.println(d); System.out.println(e); } } EDIT:: The only thing default constructor does is call to super() then how come if i have a explicitly mentioned a constructor here and A has a protected variable say c which is initialized to 17 in its constructor. Should I not be explicitly calling super() to be able to see that change since I'm using my own constructor ? Why is B still getting the value of 17 through inheritance ?

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  • Determine an object's class returned by a factory method (Error: function does not take 1 arguments

    - by tzippy
    I have a factorymethod that either returns an object of baseclass or one that is of derivedclass (a derived class of baseclass). The derived class has a method virtual void foo(int x) that takes one argument. baseclass however has virtual void foo() without an argument. In my code, a factory method returns a pointer of type bar that definetly points to an object of class derivedclass. However since this is only known at runtime I get a compiler error saying that foo() does not take an argument. Can I cast this pointer to a pointer of type derivedclass? std::auto_ptr<baseclass> bar = classfactory::CreateBar(); //returns object of class derivedclass bar->foo(5); class baseclass { public: virtual void foo(); } class derivedclass : public baseclass { public: virtual void foo(int x); }

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  • Method to register method to be called when event is raised

    - by zaidwaqi
    I have a Panel which contains 20 PictureBox controls. If a user clicks on any of the controls, I want a method within the Panel to be called. How do I do this? public class MyPanel : Panel { public MyPanel() { for(int i = 0; i < 20; i++) { Controls.Add(new PictureBox()); } } // DOESN'T WORK. // function to register functions to be called if the pictureboxes are clicked. public void RegisterFunction( <function pointer> func ) { foreach ( Control c in Controls ) { c.Click += new EventHandler( func ); } } } How do I implement RegisterFunction()? Also, if there are cool C# features that can make the code more elegant, please share.

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  • please help me to solve problem

    - by davit-datuashvili
    i have operation on heap fixdown operation below is code public class HEap{ public static void fixdown(int a[],int k,int n){ while(2*k<=n){ int j=2*k; if (j<n && a[j]<a[j+1]) j++; if (!(a[k]<a[j])) break; int t=a[k]; a[k]=a[j]; a[j]=k; k=j; } } public static void main(String[]args){ int a[]=new int[]{12,15,20,29,23,22,17,40,26,35,19,51}; fixdown(a,1,a.length); for (int i=0;i<a.length;i++){ System.out.println(a[i]); } } } //and result is 12 29 20 40 23 22 17 3 26 35 19 51 i am interested why is 3 in the list?in the array is not

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  • Printing a list using reflection

    - by TFool
    public class Service{ String serviceName; //setter and getter } public class Version{ String VersionID; //setter and getter } public void test(Object list){ //it shd print the obtained list } List< Service list1; //Service is a Bean List< Version list2; //Version is a Bean test(list1); test(list2); Now the test method shd print the obtained list - (i.e) If the list is of type Service ,then serviceName should be printed using its getter. If the list type is Version versionID should be printed. Is it possible to achieve this without using Interface or abstract class?

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  • Why does Generic class signature requires specifying new() if type T needs instantiation ?

    - by this. __curious_geek
    I'm writing a Generic class as following. public class Foo<T> : where T : Bar, new() { public void MethodInFoo() { T _t = new T(); } } As you can see the object(_t) of type T is instantiated at run-time. To support instantiation of generic type T, language forces me to put new() in the class signature. I'd agree to this if Bar is an abstract class but why does it need to be so if Bar standard non-abstract class with public parameter-less constructor. compiler prompts following message if new() is not found. Cannot create an instance of the variable type 'T' because it does not have the new() constraint

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  • Min-Ordered Bionomial Heap Insertion java

    - by Charodd Richardson
    Im writing a java code to make a min-ordered Binomial Heap and I have to Insert and Remove-min. I'm having a very big problem inserting into the Heap. I have been stuck on this for a couple of days now and it is due tomorrow. Whenever I go to insert, It only prints out the item I insert instead of the whole tree (which is in preorder). Such as if I insert 1 it prints (1) and then I go to insert 2 it prints out (2) instead of (1(2)) It keeps printing out only the number I insert last instead of the whole preordered tree. I would be very grateful if someone could help me with this problem. Thank you so much in advance, Here is my code. public class BHeap { int key; int degree;//The degree(Number of children) BHeap parent, leftmostChild, rightmostChild, rightSibling,root,previous,next; public BHeap(){ key =0; degree=0; parent =null; leftmostChild=null; rightmostChild=null; rightSibling=null; root=null; previous=null; next=null; } public BHeap merge(BHeap x, BHeap y){ BHeap newHeap = new BHeap(); y.rightSibling=x.root; BHeap currentHeap = y; BHeap nextHeap = y.rightSibling; while(currentHeap.rightSibling !=null){ if(currentHeap.degree==nextHeap.degree){ if(currentHeap.key<nextHeap.key){ if(currentHeap.degree ==0){ currentHeap.leftmostChild=nextHeap; currentHeap.rightmostChild=nextHeap; currentHeap.rightSibling=nextHeap.rightSibling; nextHeap.rightSibling=null; nextHeap.parent=currentHeap; currentHeap.degree++; } else{ newHeap = currentHeap; newHeap.rightmostChild.rightSibling=nextHeap; newHeap.rightmostChild=nextHeap; nextHeap.parent=newHeap; newHeap.degree++; nextHeap.rightSibling=null; nextHeap=newHeap.rightSibling; } } else{ if(currentHeap.degree==0){ nextHeap.rightmostChild=currentHeap; nextHeap.rightmostChild.root = nextHeap.rightmostChild;//add nextHeap.leftmostChild=currentHeap; nextHeap.leftmostChild.root = nextHeap.leftmostChild;//add currentHeap.parent=nextHeap; currentHeap.rightSibling=null; currentHeap.root=currentHeap;//add nextHeap.degree++; } else{ newHeap=nextHeap; newHeap.rightmostChild.rightSibling=currentHeap; newHeap.rightmostChild=currentHeap; currentHeap.parent= newHeap; newHeap.degree++; currentHeap=newHeap.rightSibling; currentHeap.rightSibling=null; } } } else{ currentHeap=currentHeap.rightSibling; nextHeap=nextHeap.rightSibling; } } return y; } public void Insert(int x){ /*BHeap newHeap = new BHeap(); newHeap.key=x; if(this.root==null){ this.root=newHeap; return; } else{ this.root=merge(newHeap,this.root); }*/ BHeap newHeap= new BHeap(); newHeap.key=x; if(this.root==null){ this.root=newHeap; } else{ this.root = merge(this,newHeap); }} public void RemoveMin(){ BHeap newHeap = new BHeap(); BHeap child = new BHeap(); newHeap=this; BHeap pos = newHeap.next; while(pos !=null){ if(pos.key<newHeap.key){ newHeap=pos; } pos=pos.rightSibling; } pos=this; BHeap B1 = new BHeap(); if(newHeap.previous!=null){ newHeap.previous.rightSibling=newHeap.rightSibling; B1 =pos.leftmostChild; B1.rightSibling=pos; pos.leftmostChild=pos.rightmostChild.leftmostChild; } else{ newHeap=newHeap.rightSibling; newHeap.previous.rightSibling=newHeap.rightSibling; B1 =pos.leftmostChild; B1.rightSibling=pos; pos.leftmostChild=pos.rightmostChild.leftmostChild; } merge(newHeap,B1); } public void Display(){ System.out.print("("); System.out.print(this.root.key); if(this.leftmostChild != null){ this.leftmostChild.Display(); } System.out.print(")"); if(this.rightSibling!=null){ this.rightSibling.Display(); } } }

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  • Constructor initialising an array of subobjects?

    - by ojw
    Say I have several objects within a class, each of which needs constructing with a different value. I can write something like this: class b { public: b(int num) { // 1 for a.b1, and 2 for a.b2 } }; class a { public: b b1; b b2; a() : b1(1), b2(2) { } }; However, is it possible to do the same thing if those multiple objects are stored in an array? My first attempt at it doesn't compile: class a { public: b bb[2]; a() : bb[0](1), bb[1](2) { } };

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  • The cross-thread usage of "HttpContext.Current" property and related things

    - by smwikipedia
    I read from < Essential ASP.NET with Examples in C# the following statement: Another useful property to know about is the static Current property of the HttpContext class. This property always points to the current instance of the HttpContext class for the request being serviced. This can be convenient if you are writing helper classes that will be used from pages or other pipeline classes and may need to access the context for whatever reason. By using the static Current property to retrieve the context, you can avoid passing a reference to it to helper classes. For example, the class shown in Listing 4-1 uses the Current property of the context to access the QueryString and print something to the current response buffer. Note that for this static property to be correctly initialized, the caller must be executing on the original request thread, so if you have spawned additional threads to perform work during a request, you must take care to provide access to the context class yourself. I am wondering about the root cause of the bold part, and one thing leads to another, here is my thoughts: We know that a process can have multiple threads. Each of these threads have their own stacks, respectively. These threads also have access to a shared memory area, the heap. The stack then, as I understand it, is kind of where all the context for that thread is stored. For a thread to access something in the heap it must use a pointer, and the pointer is stored on its stack. So when we make some cross-thread calls, we must make sure that all the necessary context info is passed from the caller thread's stack to the callee thread's stack. But I am not quite sure if I made any mistake. Any comments will be deeply appreciated. Thanks. ADD Here the stack is limited to user stack.

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  • Why Timer does not work if we do not generate a window?

    - by Roman
    Here is the code: import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.JFrame; import javax.swing.Timer; public class TimerSample { public static void main(String args[]) { new JFrame().setVisible(true); ActionListener actionListener = new ActionListener() { public void actionPerformed(ActionEvent actionEvent) { System.out.println("Hello World Timer"); } }; Timer timer = new Timer(500, actionListener); timer.start(); } } It generates a window and then periodically prints "Hello World Timer" in the terminal (Command Prompt). If I comment this line new JFrame().setVisible(true); the application do not print anything to the command line. Why?

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  • Singletons and constants

    - by devoured elysium
    I am making a program which makes use of a couple of constants. At first, each time I needed to use a constant, I'd define it as //C# private static readonly int MyConstant = xxx; //Java private static final int MyConstant = xxx; in the class where I'd need it. After some time, I started to realise that some constants would be needed in more than one class. At this time, I had 3 choises: To define them in the different classes that needed it. This leads to repetition. If by some reason later I need to change one of them, I'd have to check in all classes to replace them everywhere. To define a static class/singleton with all the constants as public. If I needed a constant X in ClassA, ClassB and ClassC, I could just define it in ClassA as public, and then have ClassB and ClassC refer to them. This solution doesn't seem that good to me as it introduces even more dependencies as the classes already have between them. I ended up implementing my code with the second option. Is that the best alternative? I feel I am probably missing some other better alternative. What worries me about using the singleton here is that it is nowhere clear to a user of the class that this class is using the singleton. Maybe I could create a ConstantsClass that held all the constants needed and then I'd pass it in the constructor to the classes that'd need it? Thanks

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  • How to implement fluent interface with a base class, in C++

    - by Vincenzo
    How can I implement this fluent interface in C++: class Base { public: Base& add(int x) { return *this; } } class Derived : public Base { public: Derived& minus(int x) { return *this; } } Derived d; d.add(1).minus(2).add(3).minus(4); Current code doesn't work since Base class doesn't know anything about Derived class, etc. I would be very thankful for a hint/suggestion.

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  • Injecting single-use object into class

    - by moteutsch
    I have the following code: <?php class X { public function do($url) { $httpRequest = new \HttpRequest\Curl($url, $this->getOptions()); $httpRequest->fire(); // etc. } // ... } In order to be able to unit test this class, I'd like to inject a mocked HttpRequest class. One way to do this would be as follows: <?php class X { private $httpRequestClass; public function __construct($httpRequestClass = '\HttpRequest\Curl') { $this->httpRequestClass = $httpRequestClass; } public function do($url) { $httpRequest = new $this->httpRequestClass($url, $this->getOptions()); $httpRequest->fire(); // etc. } // ... } But this doesn't seem right. Any other ideas?

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  • Shares Not working

    - by Crash893
    I'm running a ms server 2012 box acting as a file server, I've set up 4 shares (IT SECURITY PUBLIC HR) to start out with each share has its corresponding group as full permissions to the folder however when I access the server \server\it it says i don't have permissions. Public has NTLM AUTH as its full read/write and i can't even get into that Clearly im doing something wrong but im very new to windows server and im not sure how to start trouble shooting.

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  • Is read-only auto-imlemented property possible?

    - by abatishchev
    Hello. I found a topic on MSDN that talks that yes, this is possible. I did a test that seems to break this statement: using System; namespace Test { class Program { static void Main(string[] args) { Foo f = new Foo("1"); Console.WriteLine(f.Bar); // prints 1 f.Test("2"); Console.WriteLine(f.Bar);// successfully prints 2 } } class Foo { public Foo(string b) { this.Bar = b; } public string Bar { get; private set; } public void Test(string b) { // this would be impossible for readonly field! // next error would be occur: CS0191 or CS0191 // A readonly field cannot be assigned to (except in a constructor or a variable initializer) this.Bar = b; } } } Where am I wrong?

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  • FLEX, Actionscript: how can I invoke a CustomEvent ?

    - by Patrick
    hi, I've created a custom MouseEvent in Flex: package { import flash.events.MouseEvent; public class CustomMouseEvent extends MouseEvent { public var tags:Array = new Array(); public function CustomMouseEvent(type:String, tags:Array) { super(type, true); this.tags = tags; } } } Now I would like to understand how to pass the parameter tags from both Actionscript and MXML: From actionscript I'm trying something like this, but it doesn't work: newTag.addEventListener(MouseEvent.MOUSE_UP, dispatchEvent(new CustomMouseEvent(MouseEvent.MOUSE_UP,[newTag.name]))); From MXML i'm doing this and it doesn't work as well: <mx:LinkButton click="dispatchEvent(new CustomMouseEvent(MouseEvent.MOUSE_UP, bookmarksRepeater.currentItem.tags))" /> thanks

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  • EF Stored Procedure Complex Type

    - by Web Dev
    I am using EF4. I am somewhat confused on on the Entity Framework Complex name. When I go to Functional Import of a Stored Procedure name and it ask me to type in the Complex name, is that supposed to be the name of of a class that can handle that output. For examle, say if my stored procedure returns FirstName, LastName. Is the Complex name supposed to be a class that can handle that output in this case PersonName? public class PersonName { public string FirstName {get; set;} public string LastName {get;set} }

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  • how to print not mapped value

    - by IcanMakeIt
    I am using complicated SQL queries, i have to use SqlQuery ... in simple way: MODEL: public class C { public int ID { get; set; } [NotMapped] public float Value { get; set; } } CONTROLLER: IEnumerable<C> results = db.C.SqlQuery(@"SELECT ID, ATAN(-45.01) as Value from C); return View(results.ToList()); VIEW: @model IEnumerable<C> @foreach (var item in Model) { @Html.DisplayFor(modelItem => item.Value) } and the result for item.Value is NULL. So my question is , how can i print the computed value from SQL Query ? Thank you for help.

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  • Force to call virtual base function instead of the overriden one.

    - by Roberto Sebestyen
    In the following example "Test that v1 function was called" fails. Is there a way to force call the base implementation of "RunFunction" through an instance of "class V2" ?? class V1 { public virtual string RunFunction() { return "V1"; } } class V2 : V1 { public override string RunFunction() { return "V2"; } } [Test] public void TestCall() { var v1 = (V1)new V2(); var v2 = new V2(); Assert.IsTrue(v1.RunFunction() == "V1", "Test that v1 function was called"); Assert.IsTrue(v2.RunFunction() == "V2", "Test that v2 function was called"); }

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  • C++: Could Polymorphic Copy Constructors work?

    - by 0xC0DEFACE
    Consider: class A { public: A( int val ) : m_ValA( val ) {} A( const A& rhs ) {} int m_ValA; }; class B : public A { public: B( int val4A, int val4B ) : A( val4A ), m_ValB( val4B ) {} B( const B& rhs ) : A( rhs ), m_ValB( rhs.m_ValB ) {} int m_ValB; }; int main() { A* b1 = new B( 1, 2 ); A* b2 = new A( *b1 ); // ERROR...but what if it could work? return 0; } Would C++ be broken if "new A( b1 )" was able to resolve to creating a new B copy and returning an A? Would this even be useful?

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  • Proper way to 100% wakes my device?

    - by quiel
    Do you have better way to make the device awakes by 100%? I repeatedly call the acquire() but I'm not sure if that is correct. Or should I just call the acquire() once? Or should I make use of Intent.ACTION_SCREEN_OFF? public class MyServiceThatKeepsTheDeviceAwake extends IntentService { ... @Override public void onCreate() { super.onCreate(); mPowerManager = (PowerManager) getSystemService(Context.POWER_SERVICE); mWakeLock = mPowerManager.newWakeLock(PowerManager.FULL_WAKE_LOCK |PowerManager.ACQUIRE_CAUSES_WAKEUP |PowerManager.ON_AFTER_RELEASE, TAG); } @Override public void onStart(Intent intent, int startId) { super.onStart(intent, startId); mWakeLock.acquire(); } // No release

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  • Is there any alternative way of writing this switch statement(C#3.0)

    - by Newbie
    Can it be done in a better way public static EnumFactorType GetFactorEnum(string str) { Standardization e = new Standardization(); switch (str.ToLower()) { case "beta": e.FactorType = EnumFactorType.BETA; break; case "bkp": e.FactorType = EnumFactorType.BOOK_TO_PRICE; break; case "yld": e.FactorType = EnumFactorType.DIVIDEND_YIELD; break; case "growth": e.FactorType = EnumFactorType.GROWTH; break; case "mean": e.FactorType = EnumFactorType.MARKET_CAP; break; case "momentum": e.FactorType = EnumFactorType.MOMENTUM; break; case "size": e.FactorType = EnumFactorType.SIZE; break; case "stat_fact1": e.FactorType = EnumFactorType.STAT_FACT_1; break; case "stat_fact2": e.FactorType = EnumFactorType.STAT_FACT_2; break; case "value": e.FactorType = EnumFactorType.VALUE; break; } return e.FactorType; } If I create a Static class(say Constatant) and declare variable like public static string BETA= "beta"; and then if I try to put that in the Case expression like Case Constants.BETA : e.FactorType = EnumFactorType.BETA; break; then the compiler will report error.(quite expected) So is there any other way?(I canot change the switch statement) Using C#3.0 Thanks

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  • AccountModel into a Repository and Interface

    - by Jemes
    I'm trying to separate the default AccountModel in mvc2 into a separate interface and repository. I've created an Interface and Repository and copied over the code from the AccountModel. I can register users and create accounts but in Visual Studio I'm getting the error below on the AccountController (* below). Error 1 Inconsistent accessibility: parameter type 'Admin.Models.IMembershipService' is less accessible than method 'Admin.Controllers.AccountController.AccountController(Admin.Models.IMembershipService) public class AccountController : Controller { private IMembershipService MembershipService; public AccountController() : this(new dao_MembershipService()) { } public **AccountController**(IMembershipService repository) { MembershipService = repository; } Does anyone know how I could fix the error?

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  • question about random select

    - by davit-datuashvili
    here is code print number in decreasing order import java.util.*; public class select { public static void Select(int m,int n){ Random r=new Random(); if (m>0) if (r.nextInt(0x3fff8001) % n <m ){ System.out.println(n-1); Select(m-1,n-1); } else{ Select(m,n-1); } } public static void main(String[]args){ int m=35; int n=200; Select(m,n); } } and question is how to changes code such that print number in increasing order? please help

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