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• How to render the properties of the view model's base class first when using ViewData.ModelMetadata.

  - by Martin R-L

  When I use the ViewData.ModelMetadata.Properties in order to loop the properties (with an additional Where(modelMetadata => modelMetadata.ShowForEdit && !ViewData.TemplateInfo.Visited(modelMetadata))), and thereby create a generic edit view, the properties of the view model's base class are rendered last. Is it possible to use a clever OrderBy() or is there another way to first get the properties of the base class, and then the sub class'? Reverse won't do the trick since the ordering of each class' properties is perfectly fine. A workaround would of course be composition + delegation, but since we don't have mixins, it's too un-DRY IMHO, why I seek a better solution if possible.

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• How to instanciate a class when its property members are not of primitive types?

  - by Richard77

  Hello, 1) Let's say I've a class MyDataInfo public class MyDataInfo { public int MyDataInfoID { get; set; } public string Name { get; set; } } For the purpose of the fuctionality I'm after, I've created another class (MyData) whose property members are of MyDataInfo type. 2) Here's myData public class MyData { public MyDataInfo Prop1 { get; set; } public MyDataInfo Prop2 { get; set; } } 3) And, here's my action method public ActionResult MyAction() { MyData myObject = new MyData(); return View(myObject); } 4) Finally, this in my View template (which is strongly typed and inherits from MyData) <% = Html.Encode (Model.Prop1.Name)%> <% = Html.Encode (Model.Prop2.Name)%> Unfortunately, I got an error "Object not set to an instance of an object." Am I missing something or is there a different way of obtaining the same result? Thanks for helping

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• Is there a way to restrict access to a public method to only a specific class in C#?

  - by Anon

  I have a class A with a public method in C#. I want to allow access to this method to only class B. Is this possible? UPDATE: This is what i'd like to do: public class Category { public int NumberOfInactiveProducts {get;} public IList<Product> Products {get;set;} public void ProcessInactiveProduct() { // do things... NumberOfInactiveProducts++; } } public class Product { public bool Inactive {get;} public Category Category {get;set;} public void SetInactive() { this.Inactive= true; Category.ProcessInactiveProduct(); } } I'd like other programmers to do: var prod = Repository.Get<Product>(id); prod.SetInactive(); I'd like to make sure they don't call ProcessInactiveProduct manually: var prod = Repository.Get<Product>(id); prod.SetInactive(); prod.Category.ProcessInactiveProduct(); I want to allow access of Category.ProcessInactiveProduct to only class Product. Other classes shouldn't be able to call Category.ProcessInactiveProduct.

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• IEnumerable and IEnumerator in the same class, bad idea?

  - by David Rutten

  Is this a bad idea? Private Class GH_DataStructureEnumerator(Of Q As Types.IGH_Goo) Implements IEnumerable(Of Q) Implements IEnumerator(Of Q) .... .... 'Current, MoveNext, Reset etc.' .... .... Public Function GetEnumerator_Generic() As IEnumerator(Of Q) _ Implements IEnumerable(Of Q).GetEnumerator Return Me End Function End Class This class is only visible as an IEnumerable(Of T) readonly property, and it saves me an additional class that wraps IEnumerator(Of T). But somehow it just seems wrong. Is there a better way?

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• Do I assign different or the same class id to 32-bit and 64-bit versions of the same IFilter?

  - by sharptooth

  I've implemented my own Microsoft Search IFilter. I need two versions of it - 32-bit and 64-bit for deploying them on corresponding systems. In case of IFilters for any file extension I can only register one IFilter class id. Which means I can only use one version on any system. So having two class ids seems useless - it only makes the automatic installer more complex. Do I reuse the same COM class id for both or do I use different class ids?

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• mysql GROUP_CONCAT

  - by user301766

  I want to list all users with their corropsonding user class. Here are simplified versions of my tables CREATE TABLE users ( user_id INT NOT NULL AUTO_INCREMENT, user_class VARCHAR(100), PRIMARY KEY (user_id) ); INSERT INTO users VALUES (1, '1'), (2, '2'), (3, '1,2'); CREATE TABLE classes ( class_id INT NOT NULL AUTO_INCREMENT, class_name VARCHAR(100), PRIMARY KEY (class_id) ); INSERT INTO classes VALUES (1, 'Class 1'), (2, 'Class 2'); And this is the query statement I am trying to use but is only returning the first matching user class and not a concatenated list as hoped. SELECT user_id, GROUP_CONCAT(DISTINCT class_name SEPARATOR ",") AS class_name FROM users, classes WHERE user_class IN (class_id) GROUP BY user_id; Actual Output +---------+------------+ | user_id | class_name | +---------+------------+ | 1 | Class 1 | | 2 | Class 2 | | 3 | Class 1 | +---------+------------+ Wanted Output +---------+---------------------+ | user_id | class_name | +---------+---------------------+ | 1 | Class 1 | | 2 | Class 2 | | 3 | Class 1, Class 2 | +---------+---------------------+ Thanks in advance

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• Private Java class properties mysteriously reset between method calls....

  - by Michael Jones

  I have a very odd problem. A class property is mysteriously reset between method calls. The following code is executed so the constructor is called, then the parseConfiguration method is called. Finally, processData is called. The parseConfiguration method sets the "recursive" property to "true". However, as soon as it enters "processData", "recursive" becomes "false". This problem isn't isolated to a single class -- I have several examples of this in my code. How can this possibly be happening? I've tried initialising properties when they're declared outside any methods, I've tried initialising them in constructors... nothing works. The only complication I can think of here is that this class is invoked by an object that runs in a thread -- but here is one instance per thread, so surely no chance that threads are interfering. I've tried setting both methods to "synchronized", but this still happens. Please help! /** * This class or its superclasses are NOT threaded and don't extend Thread */ public class DirectoryAcquirer extends Manipulator { /** * @var Whether to recursively scan directories */ private boolean recursive = false; /** * Constructor */ public DirectoryAcquirer() { } /** * Constructor that initialises the configuration * * @param config * @throws InvalidConfigurationException */ public DirectoryAcquirer(HierarchicalConfiguration config) throws InvalidConfigurationException { super(config); } @Override protected void parseConfiguration() throws InvalidConfigurationException { // set whether to recurse into directories or not if (this.config.containsKey("recursive")) { // this.recursive gets set to "true" here this.recursive = this.config.getBoolean("recursive"); } } @Override public EntityCollection processData(EntityCollection data) { // here this.recursive is "false" this.logger.debug("processData: Entered method"); } }

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• What should I name my files with generic class definitions?

  - by Tomas Lycken

  I'm writing a couple of classes that all have generic type arguments, but I need to overload the classes because I need a different number of arguments in different scenarios. Basically, I have public class MyGenericClass<T> { ... } public class MyGenericClass<T, K> { ... } public class MyGenericClass<T, K, L> { ... } // it could go on forever, but it won't... I want them all in the same namespace, but in one source file per class. What should I name the files? Is there a best practice?

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• ORM framework that extends base class with database-implementation.

  - by aioobe

  I have a game consisting of a client / server + a webpage. A central notion in both client and game-/webserver is an Account. Accounts are stored in a database thus I'm in need of some ORM and recently had a look at Hibernate and Cayenne. My understanding however, is that both frameworks provide an "DatabaseBackedAccount"-class which I extend with my other Account methods. My problem is that the Account class is reused heavily on the client side, and I would obviously not want to include database-related code on the client implementation. My current solution is to have an Account class (shared by server and client) and extend this with a DatabaseBackedAccount (overriding setter-methods and providing a commit method) on the server side. I find this quite natural and nice, however I've had to implement all gory sql-details and ORM myself. Is there any way to "turn the table" in any existing ORM framework, so that the generated classes extend my existing class?

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• Who calls the Destructor of the class when operator delete is used in multiple inheritance.

  - by dicaprio-leonard

  This question may sound too silly, however , I don't find concrete answer any where else. With little knowledge on how late binding works and virtual keyword used in inheritance. As in the code sample, when in case of inheritance where a base class pointer pointing to a derived class object created on heap and delete operator is used to deallocate the memory , the destructor of the of the derived and base will be called in order only when the base destructor is declared virtual function. Now my question is : 1) When the destructor of base is not virtual, why the problem of not calling derived dtor occur only when in case of using "delete" operator , why not in the case given below: derived drvd; base *bPtr; bPtr = &drvd; //DTOR called in proper order when goes out of scope. 2) When "delete" operator is used, who is reponsible to call the destructor of the class? The operator delete will have an implementation to call the DTOR ? or complier writes some extra stuff ? If the operator has the implementation then how does it looks like , [I need sample code how this would have been implemented]. 3) If virtual keyword is used in this example, how does operator delete now know which DTOR to call? Fundamentaly i want to know who calls the dtor of the class when delete is used. Sample Code class base { public: base() { cout<<"Base CTOR called"<<endl; } virtual ~base() { cout<<"Base DTOR called"<<endl; } }; class derived:public base { public: derived() { cout<<"Derived CTOR called"<<endl; } ~derived() { cout<<"Derived DTOR called"<<endl; } }; I'm not sure if this is a duplicate, I couldn't find in search. int main() { base *bPtr = new derived(); delete bPtr;// only when you explicitly try to delete an object return 0; }

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• Is a class that is hard to unit test badly designed?

  - by Extrakun

  I am now doing unit testing on an application which was written over the year, before I started to do unit-testing diligently. I realized that the classes I wrote are hard to unit test, for the following reasons: Relies on loading data from database. Which means I have to setup a row in the table just to run the unit test (and I am not testing database capabilities). Requires a lot of other external classes just to get the class I am testing to its initial state. On the whole, there don't seem to be anything wrong with the design except that it is too tightly coupled (which by itself is a bad thing). I figure that if I have written automated test cases with each of the class, hence ensuring that I don't heap extra dependencies or coupling for the class to work, the class might be better designed. Does this reason holds water? What are your experiences?

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• Is there something like a Filestorage class to store files in?

  - by nebukadnezzar

  Is there something like a class that might be used to store Files and directories in, just like the way Zip files might be used? Since I haven't found any "real" class to write Zip files (real class as in real class), It would be nice to be able to store Files and Directories in a container-like file. A perfect API would probably look like this: int main() { ContainerFile cntf("myContainer.cnt", ContainerFile::CREATE); cntf.addFile("data/some-interesting-stuff.txt"); cntf.addDirectory("data/foo/"); cntf.addDirectory("data/bar/", ContainerFile::RECURSIVE); cntf.close(); } ... I hope you get the Idea. Important Requirements are: The Library must be crossplatform anything *GPL is not acceptable in this case (MIT and BSD License are) I already played with the thought of creating an Implentation based on SQLite (and its ability to store binary blobs). Unfortunately, it seems impossible to store Directory structures in a SQLite Database, which makes it pretty much useless in this case. Is it useless to hope for such a class library?

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• How to trigger the event together on each two deferent class.

  - by XBasic3000

  I have two object class on a single unit, is it posible to trigger the two events? let say the FIRSTCLASS event is fired, The SECONDCLASS also will fired? Assuming...... //{Class 1}------------------------------------------------------------- type TOnEventTrigger = procedure(Sender : Tobject; Value :integer); TMyFirstClass = Class(Tcomponent) private .... public .... OnEventTrigger : TOnEventTrigger read Fevent write Fevent; end; procedure TMyFirstClass.FEvnt(Sender : Tobject; Value :integer); begin // here is normaly triggers the event // if Assigned(OnEventTrigger) then OnEventTrigger(Self,FSomevalue); // POSTMessage(GetForegroundWindow,WM_USER+3,0,0); // this is what i did here to get the result of FSomevalue // but this is not ideal. It work only on focus window. end; //{Class 2}------------------------------------------------------------- type TOnEventTrigger = procedure(Sender : Tobject; Value :integer); TMySecondClass = Class(Tobject) private .... public .... OnEventTrigger : TOnEventTrigger; read Fevent write Fevent; end; procedure TMySecondClass.FEvnt(Sender : Tobject; Value :integer); begin // I wanted here to trigger, whenenver the above is fired // if Assigned(OnEventTrigger) then OnEventTrigger(Self,FSomevalue); end;

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• XNA Class Design with Structs as Properties and issues because they are value types and not referenc

  - by Nate Bross

  I'm wondering how you'd recommend designin a class, given the fact that XNA Framework uses Struct all over the place? For example, a spite class, which may require a Vector2 and a Rectangle (both defined as Struct) to be accessed outside of the class. The issue come in when you try to write code like this: class Item { public Vetor2 Position {get; set;} public Item() { Position = new Vector2(5,5); } } Item i = new Item(); i.Positon.X = 20; // fails with error 'Cannot modify the return value of Item because it is not a variable.' // you must write code like this var pos = i.Position; pos.X++; i.Position = pos; The second option compiles and works, but it is just butt ugly. Is there a better way?

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• Is It Possible To Spring Autowire the same Instance of a protoype scoped class in two places

  - by Mark

  Hi ** changed the example to better express the situation i am using spring 2.5 and have the following situation @Component @Scope("prototype") Class Foo { } class A { @Autowired Foo fooA; } class B { @Autowired Foo fooB; } class C { @Autowired Foo fooC; } i am trying to understand if there is some way to use @Autowired and bind the same instance of FOO onto fooA and fooB while binding a different instance to fooC i understand that if the scope of FOO will be singleton it will work but i am wandering if there is a way to achieve the same goal while using a protoype scope. also please explain is this the correct usage of the autowiring concept ? am i trying to abuse the spring framework purpose

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• C#: Problem trying to resolve a class when two namespaces are simmilar.

  - by rally25rs

  I'm running into an issue where I can't make a reference to a class in a different namespace. I have 2 classes: namespace Foo { public class Class1 { ... } } namespace My.App.Foo { public class Class2 { public void SomeMethod() { var x = new Foo.Class1; // compile error! } } } The compile error is: The type or namespace name 'Class1' does not exist in the namespace 'My.App.Foo' In this situation, I can't seem to get Visual Studio to recognize that "Foo.Class1" refers to the first class. If I mouse-over "Foo", it shows that its trying to resolve that to "My.App.Foo.Class1" If I put the line: using Foo; at the top of the .cs file that contains Class2, then it also resolves that to "My.App.Foo". Is there some trick to referencing the right "Foo" namespace without just renaming the namespaces so they don't conflict? Both of these namespaces are in the same assembly.

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• Associating a modifyable settings file with a class library in C# ?

  - by mishal153

  I have a class library(abc.dll) in which i have used a settings file. An exe (app.exe) references this class library. At runtime if i want to change the values of the settings without having to rebuild the class library/application, what is the best way to approach this problem ? In my current approach the setting values get embeded in the library, and thus i dont see any way to update them without rebuilding the whole thing.

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• In a class with no virtual methods or superclass, is it safe to assume (address of first member vari

  - by Jeremy Friesner

  Hi all, I made a private API that assumes that the address of the first member-object in the class will be the same as the class's this-pointer... that way the member-object can trivially derive a pointer to the object that it is a member of, without having to store a pointer explicitly. Given that I am willing to make sure that the container class won't inherit from any superclass, won't have any virtual methods, and that the member-object that does this trick will be the first member object declared, will that assumption hold valid for any C++ compiler, or do I need to use the offsetof() operator (or similar) to guarantee correctness? To put it another way, the code below does what I expect under g++, but will it work everywhere? class MyContainer { public: MyContainer() {} ~MyContainer() {} // non-virtual dtor private: class MyContained { public: MyContained() {} ~MyContained() {} // Given that the only place Contained objects are declared is m_contained // (below), will this work as expected on any C++ compiler? MyContainer * GetPointerToMyContainer() { return reinterpret_cast<MyContainer *>(this); } }; MyContained m_contained; // MUST BE FIRST MEMBER ITEM DECLARED IN MyContainer int m_foo; // other member items may be declared after m_contained float m_bar; };

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• Getting a seg fault, having trouble with classes and variables.

  - by celestialorb

  Ok, so I'm still learning the ropes of C++ here so I apologize if this is a simple mistake. I have this class: class RunFrame : public wxFrame { public: RunFrame(); void OnKey(wxKeyEvent& keyEvent); private: // Configuration variables. const wxString *title; const wxPoint *origin; const wxSize *size; const wxColour *background; const wxColour *foreground; const wxString *placeholder; // Control variables. wxTextCtrl *command; // Event table. DECLARE_EVENT_TABLE() }; ...then in the OnKey method I have this code: void RunFrame::OnKey(wxKeyEvent& keyEvent) { // Take the key and process it. if(WXK_RETURN == keyEvent.GetKeyCode()) { bool empty = command -> IsEmpty(); } // Propogate the event through. keyEvent.Skip(); } ...but my program keeps seg faulting when it reaches the line where I attempt to call the IsEmpty method from the command variable. My question is, "Why?" In the constructor of the RunFrame class I can seemingly call methods for the command variable in the same way I'm doing so in the OnKey method...and it compiles correctly, it just seg faults on me when it attempts to execute that line. Here is the code for the constructor if necessary: RunFrame::RunFrame() : wxFrame(NULL, wxID_ANY, wxT("DEFAULT"), wxDefaultPosition, wxDefaultSize, wxBORDER_NONE) { // Create the styling constants. title = new wxString(wxT("RUN")); origin = new wxPoint(0, 0); size = new wxSize(250, 25); background = new wxColour(33, 33, 33); foreground = new wxColour(255, 255, 255); placeholder = new wxString(wxT("command")); // Set the styling for the frame. this -> SetTitle(*title); this -> SetSize(*size); // Create the panel and attach the TextControl to it. wxPanel *panel = new wxPanel(this, wxID_ANY, *origin, *size, wxBORDER_NONE); // Create the text control and attach it to the panel. command = new wxTextCtrl(panel, wxID_ANY, *placeholder, *origin, *size); // Set the styling for the text control. command -> SetBackgroundColour(*background); command -> SetForegroundColour(*foreground); // Connect the key event to the text control. command -> Connect(wxEVT_CHAR, wxKeyEventHandler(RunFrame::OnKey)); // Set the focus to the command box. command -> SetFocus(); } Thanks in advance for any help you can give! Regards, celestialorb

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• How to tell whether a class/method is accessible using reflection?

  - by Qwertie

  I use a Dynamic Assembly to create derived classes at run time. How can I tell, using reflection, whether the base class and individual methods in the base class can be used/called from within the derived class in the dynamic assembly?

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• Why does C# allow abstract class with no abstract members?

  - by fatcat1111

  The C# spec, section 10.1.1.1, states: An abstract class is permitted (but not required) to contain abstract members. This allows me to create classes like this: public abstract class A { public void Main() { // it's full of logic! } } This is really a concrete class; it's only abstract in so far as one can't instantiate it. If inheritors don't actually have to provide implementation, then why call it abstract?

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• JNI cached jclass global reference variables being garbage collected?

  - by bubbadoughball

  I'm working in the JNI Invocation API, calling into Java from C. I have some upfront initialization to cache 30+ Java classes into global references. The results of FindClass are passed into NewGlobalRef to acquire a global reference to the class. I'm caching these class variables to reuse them later. I have 30+ global references to classes (and 30+ global methodIDs for the class constructors). In the following sample, I've removed exception handling as well as JNI invocation for the purpose of shortening the code snippet. My working code has exception checks after every JNI call and I'm running with -Xcheck:jni. Here's the snippet: jclass aClass; jclass bClass; jmethodID aCtor; jmethodID bCtor; void getGlobalRef(const char* clazz, jclass* globalClass) { jclass local = (*jenv)->FindClass(jenv,clazz); if (local) { *globalClass = (jclass) (*jenv)->NewGlobalRef(jenv,local); (*jenv)->DeleteLocalRef(jenv,local); } } methodID getMethodID(jclass clazz, const char* method, const char* sig) { return (*jenv)->GetMethodID(jenv,clazz,method,sig); } void initializeJNI() { getGlobalRef("MyProj/Testclass1", &aclass); getGlobalRef("MyProj/Testclass2", &bclass); . . aCtor = getMethodID(aclass,"<init>","()V"); bCtor = getMethodID(bclass,"<init>","(I)V"); } The initializeJNI() function sets the global references for jclasses and method IDs for constructors as well as some jfieldID's and some initialization of C data structures. After initialization, when I call into a JNI function using some of the cached jclasses and ctor jmethodIDs, I get a bad global or local reference calling reported from the -Xcheck:jni. In gdb, I break at the last line of initializeJNI(), and print all jclasses and jmethodIDs and the ones causing problems look to have been turned into garbage or garbage-collected (i.e. 0x00 or 0x06). Is it possible for global references to be gc'ed? Any suggestions?

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• What is more correct class name or object name in UML sequence diagram?

  - by atch

  I was just wondering if it is more correctly to as a label of objects in UML sequence diagram instead of object name (which is irrelevant in my opinion and less informative than class name) provide class name. Another thing, while returning information instead of listing all objects names would it be a better solution to just write collection; Diagram with object names: Diagram with class names: As it's clearly visible from the second diagram that it is much more informative than the first one, and I think it is more practical.

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• How do I make a class whose interface matches double, but upon which templates can be specialized?

  - by Neil G

  How do I make a class whose interface matches double, but whose templated types do not dynamic cast to double? The reason is that I have a run-time type system, and I want to be able to have a type that works just like double: template<int min_value, int max_value> class BoundedDouble: public double {}; And then inherit use template specialization to get run-time information about that type: template<typename T> class Type { etc. } template<int min_value, int max_value> class Type<BoundedDouble<min_value, max_value>> { int min() const { return min_value; } etc. } But, you can't inherit from double...

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• How to add a specific class to an input which has generated a form error?

  - by Kamil Mroczek

  I want to add a specific class to an input if an error is genereted by the input. For example, if input is empty and has required validator it shouls look like this: <dd id="login-element"> <input type="text" name="login" id="login" value="" class="input-text error" /> <ul class="errors"> <li>Value is required and can't be empty</li> </ul> </dd> class="input-text error" Please tell me how to do that.

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