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  • How do I combine similar method calls into a delegate pattern?

    - by Daniel T.
    I have three methods: public void Save<T>(T entity) { using (new Transaction()) { Session.Save(entity); } } public void Create<T>(T entity) { using (new Transaction()) { Session.Create(entity); } } public void Delete<T>(T entity) { using (new Transaction()) { Session.Delete(entity); } } As you can see, the only thing that differs is the method call inside the using block. How can I rewrite this so it's something like this instead: public void Save<T>(T entity) { TransactionWrapper(Session.Save(entity)); } public void Create<T>(T entity) { TransactionWrapper(Session.Create(entity)); } public void Save<T>(T entity) { TransactionWrapper(Session.Save(entity)); } So in other words, I pass a method call as a parameter, and the TransactionWrapper method wraps a transaction around the method call.

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  • iPhone: Run method from another view

    - by Nic Hubbard
    I have two views that I am loading, the first is a view with an MKMapView, the second has a table view. I would like to access a method in the first views controller, from the second view. I have been told to use the delegate for this, but I can't get it right. In my app delegate, I have set up added properties for the class of my first view. Then, in my second view, I try to access the first view using the delegate: MyAppDelegate *mainDelegate = (MyAppDelegate*) [[UIApplication sharedApplication] delegate]; Then try: [mainDelegate.mapViewControllerClass myMethodToRun]; It seems to me that it should be calling the myMethodToRun method, which is in my map view. But, it does not work. What is wrong with what I am doing here? There must be a way to access a method of another view...

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  • a constructor as a delegate - is it possible in C#?

    - by akavel
    I have a class like below: class Foo { public Foo(int x) { ... } } and I need to pass to a certain method a delegate like this: delegate Foo FooGenerator(int x); Is it possible to pass the constructor directly as a FooGenerator value, without having to type: delegate(int x) { return new Foo(x); } ? EDIT: For my personal use, the question refers to .NET 2.0, but hints/responses for 3.0+ are welcome as well.

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  • NSXMLParser 's delegate and memory leak

    - by dizzy_fingers
    Hello, I am using a NSXMLParser class in my program and I assign a delegate to it. This delegate, though, gets retained by the setDelegate: method resulting to a minor, yet annoying :-), memory leak. I cannot release the delegate class after the setDelegate: because the program will crash. Here is my code: self.parserDelegate = [[ParserDelegate alloc] init]; //retainCount:1 self.xmlParser = [[NSXMLParser alloc] initWithData:self.xmlData]; [self.xmlParser setDelegate:self.parserDelegate]; //retainCount:2 [self.xmlParser parse]; [self.xmlParser release]; ParserDelegate is the delegate class. Of course if I set 'self' as the delegate, I will have no problem but I would like to know if there is a way to use a different class as delegate with no leaks. Thank you in advance.

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  • How to make item view render rich (html) text in PyQt?

    - by Giorgio Gelardi
    I'm trying to translate code from this thread in python: import sys from PyQt4.QtCore import * from PyQt4.QtGui import * __data__ = [ "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.", "Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.", "Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.", "Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum." ] def get_html_box(text): return '''<table border="0" width="100%"><tr width="100%" valign="top"> <td width="1%"><img src="softwarecenter.png"/></td> <td><table border="0" width="100%" height="100%"> <tr><td><b><a href="http://www.google.com">titolo</a></b></td></tr> <tr><td>{0}</td></tr><tr><td align="right">88/88/8888, 88:88</td></tr> </table></td></tr></table>'''.format(text) class HTMLDelegate(QStyledItemDelegate): def paint(self, painter, option, index): model = index.model() record = model.listdata[index.row()] doc = QTextDocument(self) doc.setHtml(get_html_box(record)) doc.setTextWidth(option.rect.width()) painter.save() ctx = QAbstractTextDocumentLayout.PaintContext() ctx.clip = QRectF(0, option.rect.top(), option.rect.width(), option.rect.height()) dl = doc.documentLayout() dl.draw(painter, ctx) painter.restore() def sizeHint(self, option, index): model = index.model() record = model.listdata[index.row()] doc = QTextDocument(self) doc.setHtml(get_html_box(record)) doc.setTextWidth(option.rect.width()) return QSize(doc.idealWidth(), doc.size().height()) class MyListModel(QAbstractListModel): def __init__(self, parent=None, *args): super(MyListModel, self).__init__(parent, *args) self.listdata = __data__ def rowCount(self, parent=QModelIndex()): return len(self.listdata) def data(self, index, role=Qt.DisplayRole): return index.isValid() and QVariant(self.listdata[index.row()]) or QVariant() class MyWindow(QWidget): def __init__(self, *args): super(MyWindow, self).__init__(*args) # listview self.lv = QListView() self.lv.setModel(MyListModel(self)) self.lv.setItemDelegate(HTMLDelegate(self)) self.lv.setResizeMode(QListView.Adjust) # layout layout = QVBoxLayout() layout.addWidget(self.lv) self.setLayout(layout) if __name__ == "__main__": app = QApplication(sys.argv) w = MyWindow() w.show() sys.exit(app.exec_()) Element's size and position are not calculated correctly I guess, perhaps because I haven't understand at all the style related parts from original code. Can someone help me?

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  • iphone: Implement delegate in class

    - by Nic Hubbard
    I am trying to call up a modal table view controller using presentModalViewController but I am not sure what to do about the delegate. The following code gives me an error: MyRidesListView *controller = [[MyRidesListView alloc] init]; controller.delegate = self; [self presentModalViewController:controller animated:YES]; [controller release]; Error: Request for member 'delegate' is something not a structure or union Now, I realized there is no delegate property in my MyRidesListView class. So, how would I add a reference to my delegate there? What am I missing here?

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  • How do you pass a generic delegate argument to a method in .NET 2.0

    - by Seth Spearman
    Hello, I have a class with a delegate declaration as follows... Public Class MyClass Public Delegate Function Getter(Of TResult)() As TResult 'the following code works. Public Shared Sub MyMethod(ByVal g As Getter(Of Boolean)) 'do stuff End Sub End Class However, I do not want to explicitly type the Getter delegate in the Method call. Why can I not declare the parameter as follows... ... (ByVal g As Getter(Of TResult)) Is there a way to do it? My end goal was to be able to set a delegate for property setters and getters in the called class. But my reading indicates you can't do that. So I put setter and getter methods in that class and then I want the calling class to set the delegate argument and then invoke. Is there a best practice for doing this. I realize in the above example that I can set set the delegate variable from the calling class...but I am trying to create a singleton with tight encapsulation. For the record, I can't use any of the new delegate types declared in .net35. Answers in C# are welcome. Any thoughts? Seth

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  • Event consumption in WPF

    - by webaloman
    I have a very simple app written in Silverlight for Windows Phone, where I try to use events. In my App.xaml.cs code behind I have implemented a GeoCoordinateWatcher which registers a gCWatche_PositionChanged method. This works ok, method is called after the position has been changed. What I want to do is fire an other event lets say DBUpdatedEvent after DB has been updated in the gCWatche_PositionChanged method. For this i delclared in the App.xaml.cs public delegate void DBUpdateEventHandler(object sender, EventArgs e); and I have in my App class: public event DBUpdateEventHandler DBUpdated; the event is fired like this in the end of gCWatche_PositionChanged method like this: OnDBUpdateEvent(new EventArgs()); and also I have declared : protected virtual void OnDBUpdateEvent(EventArgs e) { if (DBUpdated != null) { DBUpdated(this, e); } } Now I need to consume this event in my other Windows Phone app page which is a separate class PhoneApplicationPage. So I declared this method in this other Phone Page: public void DBHasBeenUpdated(object sender, EventArgs e) { Debug.WriteLine("DB UPDATE EVENT CATCHED"); } And in the constructor of this page I declared: DBUpdateEventHandler dbEH = new DBUpdateEventHandler(DBHasBeenUpdated); But when I test the application event is fired (OnDBUpdateEvent is called, but DBUpdated is null, therefore DBUpdated is not called - strange) and I have a problem that the other Phone Page is not catching the event at all... Any suggestions? How to catch that event. Thanks.

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  • Namespace scoped aliases for generic types in C#

    - by TN
    Let's have a following example: public class X { } public class Y { } public class Z { } public delegate IDictionary<Y, IList<Z>> Bar(IList<X> x, int i); public interface IFoo { // ... Bar Bar { get; } } public class Foo : IFoo { // ... public Bar Bar { get { return null; //... } } } void Main() { IFoo foo; //= ... IEnumerable<IList<X>> source; //= ... var results = source.Select(foo.Bar); } The compiler says: The type arguments for method 'System.Linq.Enumerable.Select(System.Collections.Generic.IEnumerable, System.Func)' cannot be inferred from the usage. Try specifying the type arguments explicitly. It's because, it cannot convert Bar to Func<IList<X>, int, IDictionary<Y, IList<Z>>>. It would be great if I could create type namespace scoped type aliases for generic types in C#. Then I would define Bar not as a delegate, but rather I would define it as an namespace scoped alias for Func<IList<X>, int, IDictionary<Y, IList<Z>>>. public alias Bar = Func<IList<X>, int, IDictionary<Y, IList<Z>>>; I could then also define namespace scoped alias for e.g. IDictionary<Y, IList<Z>>. And if used appropriately:), it will make the code more readable. Now I have inline the generic types and the real code is not well readable:( Have you find the same trouble:)? Is there any good reason why it is not in C# 3.0? Or there is no good reason, it's just matter of money and/or time? EDIT: I know that I can use using, but it is not namespace based - not so convenient for my case.

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  • How to properly dispose of an object

    - by VoodooChild
    Hi Guys, I am experiencing something weird and have a workaround already, but I don't think I understood it well. If I call the Method below numerous times within a class: public void Method() { Foo a = new Foo(); a.Delegate1Handler = ViewSomething(); } So I am reinitializing "a" every time but for some reason a.Delegate1Handler is still around from the previous initialization, and therefore ViewSomething() is called again and again and again.... I feel like I am forgetting something critical here? Foo's guts look like: public delegate void Delegate1(T t); public Delegate1 Delegate1Handler { get; set; }

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  • Creating and releasing objects in the same method, while using self as delegate

    - by user200341
    In objective-c you are responsible for releasing objects you allocate, but what happens when you allocate an object in a method, assign self as the objects delegate, and then release the object. The callbacks from the newly created (and released) object fails at this point, or rather, doesn't happen. - (void)doSomething { MyObj *myObj = [[MyObj alloc] init]; myObj.delegate = self; [myObj performOperation]; [myObj release]; } - (void)callbackMethodFromMyObj:(NSString *)message { NSLog(message); } I can't release the object until the callback has occurred, and I can't avoid releasing the object in the same method that creates it (because it exists outside the scope). One way of doing it would be to pass the object along in the call-back and release it in the callback, but is this the right way to go about this?

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  • What is the purpose of this delegate usage?

    - by Kev
    Whilst poking around some code in .NET Reflector in an app I don't have the source code for I found this: if (DeleteDisks) { using (List<XenRef<VDI>>.Enumerator enumerator3 = list.GetEnumerator()) { MethodInvoker invoker2 = null; XenRef<VDI> vdiRef; while (enumerator3.MoveNext()) { vdiRef = enumerator3.Current; if (invoker2 == null) { // // Why do this? // invoker2 = delegate { VDI.destroy(session, vdiRef.opaque_ref); }; } bestEffort(ref caught, invoker2); } } } if (caught != null) { throw caught; } private static void bestEffort(ref Exception caught, MethodInvoker func) { try { func(); } catch (Exception exception) { log.Error(exception, exception); if (caught == null) { caught = exception; } } } Why not call VDI.destroy() directly. Is this just a way of wrapping the same pattern of try { do something } catch { log error } if it's used a lot?

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  • Question About id and Delegate Usage in Obj-C

    - by Stunner
    Ey guys, I am wondering what the following line of code is doing: @property (assign, nonatomic) id <CoursePlannerDelegate> delegate; Namely I am wondering about this portion of the line: id <CoursePlannerDelegate> delegate; It also shows up in other places: @interface CategoryAddViewController : UIViewController { UITextField *nameField, *weightField; double maxWeight; //The maximum weight that can be allocated to this Category (max value of 100) id <CategoryAddDelegate> delegate; //A Course Planner TVC } Any help appreciated, thanks in advance!

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  • C# specifying generic delegate type param at runtime

    - by smerlin
    following setup, i have several generic functions, and i need to choose the type and the function identified by two strings at runtime. my first try looked like this: public static class FOOBAR { public delegate void MyDelegateType(int param); public static void foo<T>(int param){...} public static void bar<T>(int param){...} public static void someMethod(string methodstr, string typestr) { MyDelegateType mydel; Type mytype; switch(typestr) { case "int": mytype = typeof(int); break; case "double": mytype = typeof(double); break; default: throw new InvalidTypeException(typestr); } switch(methodstr) { case "foo": mydel = foo<mytype>; //error break; case "bar": mydel = bar<mytype>; //error break; default: throw new InvalidTypeException(methodstr); } for(int i=0; i<1000; ++i) mydel(i); } } since this didnt work, i nested those switchs (a methodstr switch inside the typestr switch or viceversa), but that solution is really ugly and unmaintainable. The number of types is pretty much fixed, but the number of functions like foo or bar will increase by high numbers, so i dont want nested switchs. So how can i make this working without using nested switchs ?

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  • Get parent page values from the usercontrol

    - by Nimesh
    How to get the parent page values from the usercontrol. I have a usercontrol in a page. On click of the usercontrols button i wanna get some values from the page after executing a method. i need those values in my usercontrol. What is the best way to get the results of the page in the usercontrol.

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  • How to avoid raising an event to a closed form?

    - by Steve Dignan
    I'm having trouble handling the scenario whereby an event is being raised to a closed form and was hoping to get some help. Scenario (see below code for reference): Form1 opens Form2 Form1 subscribes to an event on Form2 (let's call the event FormAction) Form1 is closed and Form2 remains open Form2 raises the FormAction event In Form1.form2_FormAction, why does this return a reference to Form1 but button1.Parent returns null? Shouldn't they both return the same reference? If we were to omit step 3, both this and button1.Parent return the same reference. Here's the code I'm using... Form1: public partial class Form1 : Form { public Form1 () { InitializeComponent(); } private void button1_Click ( object sender , EventArgs e ) { // Create instance of Form2 and subscribe to the FormAction event var form2 = new Form2(); form2.FormAction += form2_FormAction; form2.Show(); } private void form2_FormAction ( object o ) { // Always returns reference to Form1 var form = this; // If Form1 is open, button1.Parent is equal to form/this // If Form1 is closed, button1.Parent is null var parent = button1.Parent; } } Form2: public partial class Form2 : Form { public Form2 () { InitializeComponent(); } public delegate void FormActionHandler ( object o ); public event FormActionHandler FormAction = delegate { }; private void button1_Click ( object sender , EventArgs e ) { FormAction( "Button clicked." ); } } Ideally, I would like to avoid raising events to closed/disposed forms (which I'm not sure is possible) or find a clean way of handling this in the caller (in this case, Form1). Any help is appreciated.

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  • Create empty C# event handlers automatically

    - by TomA
    It is not possible to fire an event in C# that has no handlers attached to it. So before each call it is necessary to check if the event is null. if ( MyEvent != null ) { MyEvent( param1, param2 ); } I would like to keep my code as clean as possible and get rid of those null checks. I don't think it will affect performance very much, at least not in my case. MyEvent( param1, param2 ); Right now I solve this by adding an empty inline handler to each event manually. This is error prone, since I need to remember to do that etc. void Initialize() { MyEvent += new MyEvent( (p1,p2) => { } ); } Is there a way to generate empty handlers for all events of a given class automatically using reflection and some CLR magic?

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  • C# Property Delegate?

    - by Mark
    In my other methods I could do something like this, public void Add(T item) { if (dispatcher.CheckAccess()) { ... } else { dispatcher.Invoke(new Action<T>(Add), item); } } But how do I invoke a property for a situation like this? public T this[int index] { get { ... } set { if (dispatcher.CheckAccess()) { ... } else { dispatcher.Invoke(???, index); // <-- problem is here } } }

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  • Pass an event into a constructor

    - by Vaccano
    I have a class that I want to be able the handle the mouse up event for a grid. I tried to create it with a static method call like this: MyDataBinding.BindObjectsToDataGrid(ListOfObjectsToBind, myGrid.MouseUp); The end goal being that in the method I would assign a delegate to the MouseUp PassedInMouseUp += myMethodThatWillHandleTheMouseUp; Looks good here (to me) but the compiler chokes on the first line. It says that I can only use MouseUp with a += or a -=. Clearly I am going about this the wrong way. How can I get a different class to handle the mouse up with out having to: Pass in the whole grid Expose the method that will be handling the mouse up as a public method. Or, is this just a limitation and I will have to do one of the above?

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  • passing Func<TSource, TKey> keySelector error

    - by user338429
    static void Main() { string[] a = { "a", "asd", "bdfsd", "we" }; a = a.OrderBy(fun).ToArray(); } private static int fun(string s) { return s.Length; } its is giving compile time error . I know that we can do this with Lambda expression like this. a.OrderBy(s=>s.Length).ToArray(); but i want to this do by defining different function . What mistake i have done?

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  • Translating a C# WCF app into Visual Basic

    - by MikeG
    I'm trying to write a simple/small Windows Communication Foundation service application in Visual Basic (but I am very novice in VB) and all the good examples I've found on the net are written in C#. So far I've gotten my WCF service application working but now I'm trying to add callback functionality and the program has gotten more complicated. In the C# example code I understand how everything works but I am having trouble translating into VB the portion of code that uses a delegate. Can someone please show the VB equivalent? Here is the C# code sample I'm using for reference: namespace WCFCallbacks { using System; using System.ServiceModel; [ServiceContract(CallbackContract = typeof(IMessageCallback))] public interface IMessage { [OperationContract] void AddMessage(string message); [OperationContract] bool Subscribe(); [OperationContract] bool Unsubscribe(); } interface IMessageCallback { [OperationContract(IsOneWay = true)] void OnMessageAdded(string message, DateTime timestamp); } } namespace WCFCallbacks { using System; using System.Collections.Generic; using System.ServiceModel; public class MessageService : IMessage { private static readonly List<IMessageCallback> subscribers = new List<IMessageCallback>(); //The code in this AddMessage method is what I'd like to see re-written in VB... public void AddMessage(string message) { subscribers.ForEach(delegate(IMessageCallback callback) { if (((ICommunicationObject)callback).State == CommunicationState.Opened) { callback.OnMessageAdded(message, DateTime.Now); } else { subscribers.Remove(callback); } }); } public bool Subscribe() { try { IMessageCallback callback = OperationContext.Current.GetCallbackChannel<IMessageCallback>(); if (!subscribers.Contains(callback)) subscribers.Add(callback); return true; } catch { return false; } } public bool Unsubscribe() { try { IMessageCallback callback = OperationContext.Current.GetCallbackChannel<IMessageCallback>(); if (!subscribers.Contains(callback)) subscribers.Remove(callback); return true; } catch { return false; } } } } I was thinking I could do something like this but I don't know how to pass the message string from AddMessage to DoSomething... Dim subscribers As New List(Of IMessageCallback) Public Sub AddMessage(ByVal message As String) Implements IMessage.AddMessage Dim action As Action(Of IMessageCallback) action = AddressOf DoSomething subscribers.ForEach(action) 'Or this instead of the above three lines: 'subscribers.ForEach(AddressOf DoSomething) End Sub Public Sub DoSomething(ByVal callback As IMessageCallback) 'I am also confused by: '((ICommunicationObject)callback).State 'Is that casting the callback object as type ICommunicationObject? 'How is that done in VB? End Sub

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