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  • EF4: common interface for EF entities

    - by Feryt
    Hi. I have public interface: public interface IEntity { int ID { get; set; } string Name { get; set; } bool IsEnabled { get; set; } } ehich some EF entities implements(thanks to partial class) and extesion method: public static IEnumerable<SelectListItem> ToSelectListItems<T>(this IQueryable<T> entities, int? selectedID = null) where T : IEntity { return entities.Select(c => new { c.Name, c.ID }).ToList().Select(c => new SelectListItem { Text = c.Name, Value = c.ID.ToString(), Selected = (c.ID == selectedID) }); } Calling ToSelectListItems return exception: Unable to cast the type '<EF entity name>' to type 'IEntity'. LINQ to Entities only supports casting Entity Data Model primitive types. Why, any ideas? Thank you.

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  • Java reflection for generics

    - by Vijay Bhore
    I am using Java Reflection to expose methods in custom eclipse tool. I am writing method getReturnType which accepts java.lang.reflect.Method as input and returns object of Class private static Class<?> getReturnType(Method method) { Type type = ((ParameterizedType)method.getGenericReturnType()).getRawType(); return getClass(type); } This code compiles well but at runtime i get the below exception while casting Type to ParameterizedType. java.lang.ClassCastException: java.lang.Class cannot be cast to java.lang.reflect.ParameterizedType Please suggest. Thanks!

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  • Why are there so many floats in the Android API?

    - by Brian
    The default floating point type in Java is the double. If you hard code a constant like 2.5 into your program, Java makes it a double automatically. When you do an operation on floats or ints that could potentially benefit from more precision, the type is 'promoted' to a double. But in the Android API, everything seems to be a float from sound volumes to rectangle coordinates. There's a structure called RectF used in most drawing; the F is for float. It's really a pain for programmers who are casting promoted doubles back to (float) pretty often. Don't we all agree that Java code is messy and verbose enough as it is? Usually math coprocessors and accelerators prefer double in Java because it corresponds to one of the internal types. Is there something about Android's Dalvik VM that prefers floats for some reason? Or are all the floats just a result of perversion in API design?

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  • Python appengine Query does not work when using a variable.

    - by Lloyd
    Hi, I am trying to use a fetcher method to retrieve items from my datastore. If I use the following def getItem(item_id): q = Item.all() q.filter("itemid = ", item_id) It fails because nothing is returned. If I hard code in an item like def getItem(item_id): q = Item.all() q.filter("itemid = ", 9000) it fetches just fine, and sings merrily along. I have tried every which way to get this to work. I have used result = db.GqlQuery("SELECT * FROM Item WHERE item_id = :1 LIMIT 1", title).fetch(1) to the same effect. If I hard code in a number, works fine. I have tried setting the select statement as a local string, assembling it that way, casting the int as a string, and nothing. When I output the SELECT statement to the screen, looks fine. I can cut ans paste the output into the string, and whammo, it works. Any help would be appreciated.

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  • Create Generic Class Instance from Static Method in a Derived Class

    - by user343547
    I have a class in C# with a template and static method similar to class BClass<T> { public static BClass<T> Create() { return new BClass<T>(); } } From this I derive a class and specify a template parameter to the base class class DClass : BClass<int> { } A problem occurs when I try to use the static method to create an instance of D class Program { static void Main(string[] args) { DClass d = DClass.Create(); } } Gives a compiler error "Cannot implicitly convert type 'Test.BClass<int ' to 'Test.DClass'." Adding the below cast leads to a runtime casting exception. DClass d = (DClass)DClass.Create(); Is there any succint way to allow the static method to create instances of the derived class? Ideally I would like the equivalent of a c++ typedef and I don't want the below syntax (which does work). BClass<int> d = DClass.Create();

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  • C# dependency injection - how to you inject a dependency without source?

    - by Phil Harris
    Hi, I am trying to get started with some simple dependency injection using C# and i've run up against an issue that I can't seem to come up with an answer for. I have a class that was written by another department for which I don't have the source in my project. I wanted to inject an object of this type though a constructor using an interface, but of course, i can't change the injected objects implementation to implement the interface to achieve polymorphism when casting the object to the interface type. Every academic example I have ever seen of this technique has the classes uses classes which are declared in the project itself. How would I go about injecting my dependency without the source being available in the project? I hope that makes sense, thanks.

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  • inheritance problem OOP extend

    - by hsmit
    If a Father is a Parent and a Parent is a Person and a Person has a Father I create the following: class Person{ Father father; } class Parent extends Person{} class Father extends Parent{} Instances: Person p1 = new Person(); Person p2 = new Person(); p1.father = p2; //father is of the type Father This doesn't work... Now try casting:: Person p1 = new Person(); Person p2 = new Person(); p1.father = (Father)p2; This doesn't work either. What does work for this case?

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  • Prims vs Polys: what are the pros and cons of each?

    - by Richard Inglis
    I've noticed that most 3d gaming/rendering environments represent solids as a mesh of (usually triangular) 3d polygons. However some examples, such as Second Life, or PovRay use solids built from a set of 3d primitives (cube, sphere, cone, torus etc) on which various operations can be performed to create more complex shapes. So my question is: why choose one method over the other for representing 3d data? I can see there might be benefits for complex ray-tracing operations to be able to describe a surface as a single mathematical function (like PovRay does), but SL surely isn't attempting anything so ambitious with their rendering engine. Equally, I can imagine it might be more bandwidth-efficient to serve descriptions of generalised solids instead of arbitrary meshes, but is it really worth the downside that SL suffers from (ie modelling stuff is really hard, and usually the results are ugly) - was this just a bad decision made early in SL's development that they're now stuck with? Or is it an artefact of what's easiest to implement in OpenGL?

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  • How to correctly hook and return GetDlgItemTextA from C++ to C# to C++ from EasyHook

    - by Gbps
    I'm using EasyHook, a C# library for injecting and detouring functions from unmanaged applications. I'm trying to hook onto GetDlgItemTextA, which takes the arguments: UINT WINAPI GetDlgItemText( __in HWND hDlg, __in int nIDDlgItem, __out LPTSTR lpString, __in int nMaxCount );` In my hook, I am casting it as: [DllImport("user32.dll", // CharSet = CharSet.Unicode, SetLastError = true, CallingConvention = CallingConvention.StdCall)] static extern uint GetDlgItemTextA(IntPtr hWin, int nIDDlgItem, StringBuilder text, int MaxCount); And my hook is: static uint DGetDlgItemText_Hooked(IntPtr hWin, int nIDDlgItem, StringBuilder text, int MaxCount) { // call original API... uint ret = GetDlgItemTextA(hWin, nIDDlgItem, text, MaxCount); MessageBox.Show(text.ToString()); return ret; } Unfortunately, the moment this is called, the hooked application crashes. Is there a better cast I can use to successfully hook onto this function? Thanks! I've compiled, editted, and confirmed the working condition of my EasyHook setup. This is just casing and hooking only.

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  • Me As Child Type In General Function

    - by Steven
    I have a MustInherit Parent class with two Child classes which Inherit from the Parent. How can I use (or Cast) Me in a Parent function as the the child type of that instance? EDIT: My actual goal is to be able to serialize (BinaryFormatter.Serialize(Stream, Object)) either of my child classes. However, "repeating the code" in each child "seems" wrong. EDIT2: This is my Serialize function. Where should I implement this function? Copying and pasting to each child doesn't seem right, but casting the parent to a child doesn't seem right either. Public Function Serialize() As Byte() Dim bFmt As New BinaryFormatter() Dim mStr As New MemoryStream() bFmt.Serialize(mStr, Me) Return mStr.ToArray() End Function

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  • Why is comparing against "end()" iterator legal?

    - by sharptooth
    According to C++ standard (3.7.3.2/4) using (not only dereferencing, but also copying, casting, whatever else) an invalid pointer is undefined behavior (in case of doubt also see this question). Now the typical code to traverse an STL containter looks like this: std::vector<int> toTraverse; //populate the vector for( std::vector<int>::iterator it = toTraverse.begin(); it != toTraverse.end(); ++it ) { //process( *it ); } std::vector::end() is an iterator onto the hypothetic element beyond the last element of the containter. There's no element there, therefore using a pointer through that iterator is undefined behavior. Now how does the != end() work then? I mean in order to do the comparison an iterator needs to be constructed wrapping an invalid address and then that invalid address will have to be used in a comparison which again is undefined behavior. Is such comparison legal and why?

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  • Does dynamic_cast work inside overloaded operator delete ?

    - by iammilind
    I came across this: struct Base { void* operator new (size_t); void operator delete (void*); virtual ~Base () {} // <--- polymorphic }; struct Derived : Base {}; void Base::operator delete (void *p) { Base *pB = static_cast<Base*>(p); if(dynamic_cast<Derived*>(pB) != 0) { /* ... NOT reaching here ? ... */ } free(p); } Now if we do, Base *p = new Derived; delete p; Surprisingly, the condition inside the Base::delete is not satisfied Am I doing anything wrong ? Or casting from void* looses the information of Derived* ?

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  • Extend MySQL implementation of PiP Algorithm?

    - by Mike
    I need to make a point in polygon MySQL query. I already found these two great solutions: http://forums.mysql.com/read.php?23,286574,286574 MySQL implementation of ray-casting Algorithm? But these functions can only check if one point is inside a poly. I have a query where the PiP part should only be one part of the query and check for x points inside a polygon. Something like this: $points = list/array/whatever of points in language of favour SELECT d.name FROM data AS d WHERE d.name LIKE %red% // just bla bla // how to do this ? AND $points INSIDE d.polygon AND myWithin( $points, d.polygo ) // or UPDATE I tried it with MBR functions like this: SET @g1 = GeomFromText('Polygon((13.43971 52.55757,13.41293 52.49825,13.53378 52.49574, 13.43971 52.55757))'); SET @g2 = GeomFromText('Point(13.497834 52.540489)'); SELECT MBRContains(@g1,@g2); G2 should NOT be inside G1 but MBR says it is.

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  • Diamonds Are Forever. Services Are Not.

    - by rayman
    Hi, ive read this article by Mark Murphy, while i was looking for a solution to my case. I have a Listener in my system, which suppose to get a UDP trigger times to times from an outside server, ive done this listener as a service. how could i prevent it being shut off by the user? (SDK 1.5), i`am working for a company which create cell phones, and we spread the device with this Listener. as soon as the listener goes off our systems will be terminated any idea for this scenario? *i`am already aware to the face, that the system could also take it off, but this case will be easier to handle and avoid. thanks, ray.

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  • handling broadcast reciver

    - by rayman
    Hi, I have an app which has MainActivity(without gui.. please just flow with it:) ) now this MainActivity running a service, this service using sendBroadcast() in order to comunnicate with the MainActivity.. now ofcourse i need to registerReceiver in the onResume() of the MainActivity. but i also need to add unregisterReceiver(receiver) in the onDestroy() of the MainActivity. problem is: when i first start that app i need it to up the service, and i dont want the user to lose focus, so i press finish() after i`am starting the service.. but then auto invoked also unregisterReceiver(receiver).. and this is not good for me.. i get error it's said it couldnt find any registerd reciver. so i fixed it by delete this line.. but i am sure its going to 'revenege' me in the future, when/where could i have problem if i wont use unregisterReceiver(receiver).. at the onDestroy() thanks, ray.

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  • Custom ArrayList serialization

    - by rayman
    Hi, i was trying to serialize an ArrayList which contacins custom objects. I`am serializing it in a servlet(server side), and deserialize at the client side. (using ObjectOutputStream,ObjectInputStream) it worked fine, when I work with ArrayList< String but when i tried it with ArrayList< MyObject i couldnt get any results in the client side, this is the exception: java.lang.ClassNotFoundException: web.MyObject *ofcourse that i have done this: MyObject implements Serializable ... MyObject contains only String fields in it. what have I done worng? Thanks, ray.

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  • Download Specific Images

    - by thebourneid
    I'm trying to search and download specific images /front and back cover / of a website if found but whatever I do I always download only one of them. What should I change in my code to download both of them if found? while ($title_found =~ /'(http:\/\/images.blu-ray.com\/movies\/covers\/\d+_.*?)'/gis) { $url = getSite($1); if ($title_found =~ /front/) { $filename = 'front.jpg'; } elsif ($title_found =~ /back/) { $filename = 'back.jpg'; } } my $dir = 'somepath'.$filename; open F, ">", $dir; binmode F; print F $url; close F; return 0;

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  • Checking if an element is visible in Chrome using Selenium Remote WebDriver

    - by Stuart
    Is there a cross browser solution to check if an element is visible using WebDriver? The solution for IE and firefox is to cast the object to a RenderedRemoteWebElement and then call the property Displayed. I'm using the following methods to return if a element is visible: /// <summary> /// Check if the control is visible. /// </summary> public bool IsVisible() { IWebElement control = mSelenium.FindElement(mFindBy); return ((RenderedRemoteWebElement)control).Displayed; } The problem is when I run this using Chrome, I get an exception when casting to type RenderedRemoteWebElement, this is not really the problem as I can catch this, but I need to a solution to check if an element is visible in chrome. Thanks

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  • Is It Safe to Cast Away volatile?

    - by Yan Cheng CHEOK
    Most of the time, I am doing this way. class a { public: ~ a() { i = 100; // OK delete (int *)j; // Compiler happy. But, is it safe? // Error : delete j; } private: volatile int i; volatile int *j; }; int main() { a aa; } However, I saw an article here: https://www.securecoding.cert.org/confluence/display/seccode/EXP32-C.+Do+not+access+a+volatile+object+through+a+non-volatile+reference Casting away volatile allows access to an object through a non-volatile reference. This can result in undefined and perhaps unintended program behavior. So, what will be the workaround for my above code example?

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  • Serializing System.Drawing.Color in .NET

    - by alankdkd
    Hi all, I've used the default .NET serialization for a class with a System.Drawing.Color member. The code is now in use by people, and I need to add an extra member to the class, but still deserialize older versions. So I tried the standard way of doing this: The ISerializable interface, using SerializationInfo methods to get the int and string members. The problem: My class also has a System.Drawing.Color member, but SerializationInfo doesn't provide a "GetColor" method read this data type. I've tried getting it as an int and as a string, and casting it to System.Drawing.Color, but no luck. Does anyone know how to deserialize a System.Drawing.Color from SerializationInfo? Thanx! Alan

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  • Matlab - Propagate unit vectors on to the edge of shape boundaries

    - by Graham
    Hi I have a set of unit vectors which I want to propagate on to the edge of shape boundary defined by a binary image. The shape boundary is defined by a 1px wide white edge. I also have the coordinates of these points stored in a 2 row by n column matrix. The shape forms a concave boundary with no holes within itself made of around 2500 points. What would be the best method to do this? Are there some sort of ray tracing algorithms that could be used? Or would it be a case of taking the unit vector and multiplying it by a scalar and testing after multiplication if the end point of the vector is outside the shape boundary. When the end point of the unit vector is outside the shape, just find the point of intersection? Thank you very much in advance for any help!

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  • Why do debug symbols so adversely affect the performance of threaded applications on Linux?

    - by fluffels
    Hi. I'm writing a ray tracer. Recently, I added threading to the program to exploit the additional cores on my i5 Quad Core. In a weird turn of events the debug version of the application is now running slower, but the optimized build is running faster than before I added threading. I'm passing the "-g -pg" flags to gcc for the debug build and the "-O3" flag for the optimized build. Host system: Ubuntu Linux 10.4 AMD64. I know that debug symbols add significant overhead to the program, but the relative performance has always been maintained. I.e. a faster algorithm will always run faster in both debug and optimization builds. Any idea why I'm seeing this behavior?

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  • Asp.net loading a file encounters "Access to the path … is denied" in development on Windows 7

    - by ray247
    Hi there, I have an Asp.net app that simply reads an xml file and this code used to work fine on Vista with VS2008, now I just moved to Windows 7 and I migrated the code to VS2010, I encoutered “Access to the path [path to my webapp folder] is denied". Nothing else is changed, I tried to change folder perms even though I didn't think it got anything to do with that since the same code used to work fine, but still didn't get around this problem. Could someone please shed some light on why this may be happening and how to fix it? Thanks, Ray.

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  • Securing input of private / protected methods?

    - by ts
    Hello, normally, all sane developers are trying to secure input of all public methods (casting to proper types, validating, sanitizing etc.) My question is: are you in your code validating also parameters passed to protected / private methods? In my opinion it is not necessary, if you securize properly parameters of public methods and return values from outside (other classes, db, user input etc...). But I am constantly facing frameworks and apps (ie. prestashop to name one) where validation is often repeated in method call, in method body and once again for securize returned value - which, I think, is creating performace overhead and is also a sign of bad design.

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  • C99 strict aliasing rules in C++ (GCC)

    - by Checkers
    As far as I understand, GCC supports all of its C99 features in C++. But how is C99 strict aliasing handled in C++ code? I know that casting with C casts between unrelated types is not strict-aliasing-safe and may generate incorrect code, but what about C++? Since strict aliasing is not part of C++ standard (is that correct?), GCC must be specifying the semantics itself. I figure const_cast and static_cast cast between related types, hence they are safe, while reinterpret_cast can break strict aliasing rules. Is this a correct understanding?

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