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  • Why is it possible to enumerate a LinqToSql query after calling Dispose() on the DataContext?

    - by DanM
    I'm using the Repository Pattern with some LinqToSql objects. My repository objects all implement IDisposable, and the Dispose() method does only thing--calls Dispose() on the DataContext. Whenever I use a repository, I wrap it in a using person, like this: public IEnumerable<Person> SelectPersons() { using (var repository = _repositorySource.GetNew<Person>(dc => dc.Person)) { return repository.GetAll(); } } This method returns an IEnumerable<Person>, so if my understanding is correct, no querying of the database actually takes place until Enumerable<Person> is traversed (e.g., by converting it to a list or array or by using it in a foreach loop), as in this example: var persons = gateway.SelectPersons(); // Dispose() is fired here var personViewModels = ( from b in persons select new PersonViewModel { Id = b.Id, Name = b.Name, Age = b.Age, OrdersCount = b.Order.Count() }).ToList(); // executes queries In this example, Dispose() gets called immediately after setting persons, which is an IEnumerable<Person>, and that's the only time it gets called. So, a couple questions: How does this work? How can a disposed DataContext still query the database for results when I walk the IEnumerable<Person>? What does Dispose() actually do? I've heard that it is not necessary (e.g., see this question) to dispose of a DataContext, but my impression was that it's not a bad idea. Is there any reason not to dispose of it?

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  • C# Dispatcher {"The calling thread cannot access this object because a different thread owns it."}

    - by user359446
    Hi, first I need to say that I´m noob with WPF and C#. Application: Create Mandelbrot Image (GUI) My disptacher works perfektly this this case: private void progressBarRefresh(){ while ((con.Progress) < 99) { progressBar1.Dispatcher.Invoke(DispatcherPriority.Send, new Action(delegate { progressBar1.Value = con.Progress; } )); } } I get the Message (Title) when tring to do this with the below code: bmp = BitmapSource.Create(width, height, 96, 96, pf, null, rawImage, stride); this.Dispatcher.Invoke(DispatcherPriority.Send, new Action(delegate { img.Source = bmp; ViewBox.Child = img; //vllt am schluss } )); I will try to explain how my program works. I created a new Thread (because GUI dont response) for the calculation of the pixels and the colors. In this Thread(Mehtod) I´m using the Dispatcher to Refresh my Image in the ViewBox after the calculations are ready. When I´m dont put the calculation in a seperate Thread then I can refresh or build my Image. PS: Sry for my bad english

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  • What happens in memory when calling a function with literal values?

    - by Drise
    Suppose I have an arbitrary function: void someFunc(int, double, char); and I call someFunc(8, 2.4, 'a');, what actually happens? How does 8, 2.4, and 'a' get memory, moved into that memory, and passed into the function? What type of optimizations does the compiler have for situations like these? What if I mix and match parameters, such like someFunc(myIntVar, 2.4, someChar);? What happens if the function is declared as inline?

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  • When calling a static method on parent class, can the parent class deduce the type on the child (C#)

    - by Matt
    Suppose we have 2 classes, Child, and the class from which it inherits, Parent. class Parent { public static void MyFunction(){} } class Child : Parent { } Is it possible to determine in the parent class how the method was called? Because we can call it two ways: Parent.MyFunction(); Child.MyFunction(); My current approach was trying to use: MethodInfo.GetCurrentMethod().ReflectedType; // and MethodInfo.GetCurrentMethod().DeclaringType; But both appear to return the Parent type. If you are wondering what, exactly I am trying to accomplish (and why I am violating the basic OOP rule that the parent shouldn't have to know anything about the child), the short of it is this (let me know if you want the long version): I have a Model structure representing some of our data that persists to the database. All of these models inherit from an abstract Parent. This parent implements a couple of events, such as SaveEvent, DeleteEvent, etc. We want to be able to subscribe to events specific to the type. So, even though the event is in the parent, I want to be able to do: Child.SaveEvent += new EventHandler((sender, args) => {}); I have everything in place, where the event is actually backed by a dictionary of event handlers, hashed by type. The last thing I need to get working is correctly detecting the Child type, when doing Child.SaveEvent. I know I can implement the event in each child class (even forcing it through use of abstract), but it would be nice to keep it all in the parent, which is the class actually firing the events (since it implements the common save/delete/change functionality).

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  • Calling a method from another view in objective-c. (iphone sdk).

    - by MarcZero
    Hello. I am currently creating a multi-view game on the iPhone platform. I have my main view start to play some background music upon loading. I then go to another view and start the game. I am trying to get the background music from the original view to stop once I start the game. I am having trouble getting the stop playing music message to my original view. Here is the relevant info: The main view where the sound is played from is just a subView of the programViewController class called *viewController. The heading is in the programAppDelegate class. The sound is done using the AVAudioPlayer class and plays fine when the program starts up and when I navigate to other subviews that are added on by going through the menu system. In the view that I want to start the game, I attempt to call the instance of the class to turn of the player but anytime I use this format of code: [viewController #######]; It gives a build error of "viewController undeclared" no matter what I put after the "viewController" in the message.I have attempted to import the programAppDelegate.h file but it still gives the same error. I realize this might be a simple misunderstanding of the objective-c language but I cannot find any info on this issue. I am a recent convert from Java so I am trying to wrap my head around everything. Thank you for your time!

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  • Calling a webservice synchronously from a Silverlight 3 application?

    - by Lasse V. Karlsen
    I am trying to reuse some .NET code that performs some calls to a data-access-layer type service. I have managed to package up both the input to the method and the output from the method, but unfortunately the service is called from inside code that I really don't want to rewrite in order to be asynchronous. Unfortunately, the webservice code generated in Silverlight only produces asynchronous methods, so I was wondering if anyone had working code that managed to work around this? I tried the recipe found here: The Easy Way To Synchronously Call WCF Services In Silverlight, but unfortunately it times out and never completes the call. Or rather, what seems to happen is that the completed event handler is called, but only after the method returns. I am suspecting that the event handler is called from a dispatcher or similar, and since I'm blocking the main thread here, it never completes until the code is actually back into the GUI loop. Or something like that. Here's my own version that I wrote before I found the above recipe, but it suffers from the same problem: public static object ExecuteRequestOnServer(Type dalInterfaceType, string methodName, object[] arguments) { string securityToken = "DUMMYTOKEN"; string input = "DUMMYINPUT"; object result = null; Exception resultException = null; object evtLock = new object(); var evt = new System.Threading.ManualResetEvent(false); try { var client = new MinGatServices.DataAccessLayerServiceSoapClient(); client.ExecuteRequestCompleted += (s, e) => { resultException = e.Error; result = e.Result; lock (evtLock) { if (evt != null) evt.Set(); } }; client.ExecuteRequestAsync(securityToken, input); try { var didComplete = evt.WaitOne(10000); if (!didComplete) throw new TimeoutException("A data access layer web service request timed out (" + dalInterfaceType.Name + "." + methodName + ")"); } finally { client.CloseAsync(); } } finally { lock (evtLock) { evt.Close(); evt = null; } } if (resultException != null) throw resultException; else return result; } Basically, both recipes does this: Set up a ManualResetEvent Hook into the Completed event The event handler grabs the result from the service call, and signals the event The main thread now starts the web service call asynchronously It then waits for the event to become signalled However, the event handler is not called until the method above has returned, hence my code that checks for evt != null and such, to avoid TargetInvocationException from killing my program after the method has timed out. Does anyone know: ... if it is possible at all in Silverlight 3 ... what I have done wrong above?

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  • iOS: Best Way to do This w/o Calling Method 32 Times?

    - by user1886754
    I'm currently retrieving the Top 100 Scores for one of my leaderboards the following way: - (void) retrieveTop100Scores { __block int totalScore = 0; GKLeaderboard *myLB = [[GKLeaderboard alloc] init]; myLB.identifier = [Team currentTeam]; myLB.timeScope = GKLeaderboardTimeScopeAllTime; myLB.playerScope = GKLeaderboardPlayerScopeGlobal; myLB.range = NSMakeRange(1, 100); [myLB loadScoresWithCompletionHandler:^(NSArray *scores, NSError *error) { if (error != nil) { NSLog(@"%@", [error localizedDescription]); } if (scores != nil) { for (GKScore *score in scores) { NSLog(@"%lld", score.value); totalScore += score.value; } NSLog(@"Total Score: %d", totalScore); [self loadingDidEnd]; } }]; } The problem is I want to do this for 32 leaderboards. What's the best way of achieving this? Using a third party tool (Game Center Manager), I can get the following line to return a dictionary with leaderboard ID's as keys and the Top 1 highest score as values NSDictionary *highScores = [[GameCenterManager sharedManager] highScoreForLeaderboards:leaderboardIDs]; So my question is, how can I combine those 2 segments of code to pull in the 100 values for each leaderboard, resulting in a dictionary with all of the leaderboard names as keys, and the Total (of each 100 scores) of the leaderboards for values.

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  • Calling Windows commands (e.g. del) from a GNU makefile

    - by Tom
    It does not appear to be possible to call Windows system commands (e.g. del, move, etc) using GNU Make. When the following rule is run, an error is reported del: command not found: clean: del *.o This is presumably because there is no such execuatable as "del". I've also tried running it as an option to cmd but with this only seems to open a new prompt: clean: cmd /C del *.o I'm using GNU Make 3.79.1 that is bundled as part of MSys.

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  • WPF Calling a custom command on a custom control (from a viewmodel?)

    - by user190615
    I want to take a snap of the visual tree of a custom wpf control when the user clicks a button in a toolbar. The control is bound to a viewmodel. I have a BitmapSource dp in the custom control holding the snapped image which is bound to a property on my VM. The BitmapSource dp on the control is updated via a custom command on the control. I've tied the toolbar button's command to call the controls command which updates the BitmapSource. Now the problem is the end result I want is when the user clicks the button, the control updates its image and then the vm offers to save this image. I cant wrap my mind around an mvvm way of doing this. One inelegant solution is that control fires an event after the image is updated which is routed to the viewmodel as a command(command behavior) but then if i want to do something else with the image on some other button click, all the commands bound to the events will fire. All thoughts appreciated. EDIT The command on the control is a RoutedCommand and the commands in my vm are Prism delegate commands.

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  • Steps to take for figuring out the delay when calling service and loading data with the result?

    - by VoodooChild
    Hello, In a client server app, where client front end is done in silverlight using C# and the services are the WCF services. If I am to hit the service and do a query and bring back a result and I notice that it is taking a relatively long time to load my page which is just loading the grid with the data, what things should I look at fix this issue or how would I fix this issue? What steps could I take to determine the problem? where is the bottle-neck, can anyone know from the little information provided here? Does this have anything to do with serialization? Any insight on what could be causing this delay? My service calls are made async. I hope this question makes sense :) Thanks

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  • Is a string formatter that pulls variables from its calling scope bad practice?

    - by Eric
    I have some code that does an awful lot of string formatting, Often, I end up with code along the lines of: "...".format(x=x, y=y, z=z, foo=foo, ...) Where I'm trying to interpolate a large number of variables into a large string. Is there a good reason not to write a function like this that uses the inspect module to find variables to interpolate? import inspect def interpolate(s): return s.format(**inspect.currentframe().f_back.f_locals) def generateTheString(x): y = foo(x) z = x + y # more calculations go here return interpolate("{x}, {y}, {z}")

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  • Calling child constructor by casting (ChildClass)parentObject; to track revisions

    - by FreshCode
    To track revisions of a Page class, I have a PageRevision class which inherits from Page and adds a revision ID (Guid RevisionID;). If possible, how should I cast an existing Page object to a PageRevision and ensure that the PageRevision constructor is called to create a new revision ID? I could could have a PageRevision(Page page) constructor which generates the Guid and copies all the Page attributes, but I want to automate it, especially if a Page class has many attributes (and I later add one, and forget to modify the copy constructor). Desired use Page page = new Page(123, "Page Title", "Page Body"); // where 123 is page ID PageRevision revision = (PageRevision)page; // now revision.RevisionID should be a new Guid. Page, PageRevision classes: public class Page { public int ID { get; set; } public string Title { get; set; } public string Body { get; set; } } public class PageRevision : Page { public Guid RevisionID { get; set; } public PageRevision() { this.RevisionID = Guid.NewGuid(); } }

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  • How to stop calling the Activity again when device orientation is changed??

    - by user1460323
    My app uses Barcode Scanner. I want to launch the scanner when I open the app so I have it in the onCreate method. The problem is that if I have it like that, when I turn the device it calls again onCreate and calls another scanner. Also I have the first activity that calls the scanner. it has a menu so if he user presses back, it goes to that menu. If I turn the screen on that menu, it goes to barcode scanner again. To solve it I have a flag that indicates if it is the first time I call the scanner, if it's not I don't call it again. Now the problem is that if I go out of the app and go in again it doesn't go to the scanner, it goes to the menu, becasuse is not the first time I call it. Any ideas?? Is there a way to change the flag when I go out of my main activity or any other solution?? My code. private static boolean first = true; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); integrator = new IntentIntegrator(this); if (first) { first = false; integrator.initiateScan(); } }

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  • How to force calling of QWidget::paintEvent() when its hovered by other window?

    - by Pie_Jesu
    Hi there. I have occured a problem: I'm writing a widget, which displays current date's day number. It's like a button, but it's not derived from QPushButton class. Just from QWidget. So I reimplemented enterEvent(), leaveEvent(), mousePressEvent(), mouseReleaseEvent(). I call update() inside these methods and widget has realistic button behavior (paintEvent() is reimplemented too). But when I change system date and hover that widget with other window, my widget doesn't calls paintEvent() and displays old date. Only when I place mouse over it, widget repaints it's contents. I guess there is an option, which paints old contents on hover event to avoid unnecessary paint events. But I need to disable it. Tried to set many attributes (Qt::WidgetAttribute enum). But it doesn't helps. Please, help me (and sorry for my bad english).

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  • Is it possible to supply template parameters when calling operator()?

    - by Paul
    I'd like to use a template operator() but am not sure if it's possible. Here is a simple test case that won't compile. Is there something wrong with my syntax, or is this simply not possible? struct A { template<typename T> void f() { } template<typename T> void operator()() { } }; int main() { A a; a.f<int>(); // This compiles. a.operator()<int>(); // This compiles. a<int>(); // This won't compile. return 0; }

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  • Calling a constructor to reinitialize variables doesn't seem to work?

    - by Matt
    I wanted to run 1,000 iterations of a program, so set a counter for 1000 in main. I needed to reinitialize various variables after each iteration, and since the class constructor had all the initializations already written out - I decided to call that after each iteration, with the result of each iteration being stored in a variable in main. However, when I called the constructor, it had no effect...it took me a while to figure out - but it didn't reinitialize anything! I created a function exactly like the constructor - so the object would have its own version. When I called that, it reinitialized everything as I expected. int main() { Class MyClass() int counter = 0; while ( counter < 1000 ) { stuff happens } Class(); // This is how I tried to call the constructor initially. // After doing some reading here, I tried: // Class::Class(); // - but that didn't work either /* Later I used... MyClass.function_like_my_constructor; // this worked perfectly */ } ...Could someone try to explain why what I did was wrong, or didn't work, or was silly or what have you? I mean - mentally, I just figured - crap, I can call this constructor and have all this stuff reinitialized. Are constructors (ideally) ONLY called when an object is created?

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  • C# Why does calling an interface member from a class generate an error?

    - by Jack
    So I have an interface: interface IFoo { int Bar(); int this[int i] {get; set;} } And a class that derives from it class Foo : IFoo { public int IFoo.Bar() { //Implementation { public int IFoo.this[int i] { //Implementation } } Now, I try to do this: var fooey = new Foo(); int i = Fooey.Bar(); or this: int i = Fooey[4]; I would expect these to work properly. However, the compiler generates an error as if such members don't exist. Why is that? I am aware I can cast Foo as IFoo, but I am also aware that casting is costly to performance, which is often the reason to use interfaces in the first place. EDIT 1: These are the errors generated 'Foo' does not contain a definition for 'Bar' and no extension method 'Bar' accepting a first argument of type 'Foo' could be found (are you missing a using directive or an assembly reference?) "Cannot apply indexing to an expression of type 'Foo'"

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