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  • How to create a static delegate from main-viewcontroller?

    - by geforce
    Hi, hope someone can help me on learning some new stuff about delegates in iOS-programming. I have a "MainViewController" which is the first VC when the app starts. I´ve a kind of modelselection with different UIImageViews and after choosing one of them, i´m pushing a new VC. I want to handle the modelChoice with a delegate, so all other viewControllers can listen to that and act based on the users choice. But does that mean that i have to alloc a new instance of that "MainViewController" in every VC? Whats the solution on that? How do i create (i think its called) static delegate? Would be great to learn that.. Thanks for sharing..

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  • very simple delegate musing

    - by Ted
    Sometimes the simplest questions make me love C/C++ and C# more and more. Today sitting on the bus musing aout delegates I remembered reading somwhere you don't need to use the new keyword when instaniating a new delegate. For example: public static void SomeMethod(string message) { ... } ... public delegate void TestDelgate(string message); //Define a delegate ........... //create a new instance ..METHOD 1 TestDelgate t = new TestDelgate(SomeMethod); //OR another way to create a new instance ..METHOD 2 TestDelgate t = SomeMethod; //create a new instance ..METHOD 2 So todays questions are What happens under the hood in method 2. Does the compiler expand method 2 into method 1, hence writing TestDelgate t = SomeMethod; is just a shortcut for TestDelgate t = new TestDelgate(SomeMethod);, or is there another reason for the exsitence of method 2 Do you guys think method 1 or method 2 is better for readability (this is a subjective question, but I'd just like to get a unscientific feel of general opinion of stackoverflow :-))

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  • Delegate.CreateDelegate() and generics: Error binding to target method

    - by SDReyes
    I'm having problems creating a collection of delegate using reflection and generics. I'm trying to create a delegate collection from Ally methods, whose share a common method signature. public class Classy { public string FirstMethod<out T1, in T2>( string id, Func<T1, int, IEnumerable<T2>> del ); public string SecondMethod<out T1, in T2>( string id, Func<T1, int, IEnumerable<T2>> del ); public string ThirdMethod<out T1, in T2>( string id, Func<T1, int, IEnumerable<T2>> del ); // And so on... } And the generics cooking: // This is the Classy's shared method signature public delegate string classyDelegate<out T1, in T2>( string id, Func<T1, int, IEnumerable<T2>> filter ); // And the linq-way to get the collection of delegates from Classy ( from method in typeof( Classy ).GetMethods( BindingFlags.Instance | BindingFlags.DeclaredOnly | BindingFlags.NonPublic ) let delegateType = typeof( classyDelegate<,> ) select Delegate.CreateDelegate( delegateType, method ) ).ToList( ); But the Delegate.CreateDelegate( delegateType, method ) throws an ArgumentException saying Error binding to target method. : / What am I doing wrong?

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  • Example usage of a custom delegate in c#

    - by Freakishly
    Hi, I found this question on SO about a tree implementation in C#. I have no idea about delegates and I was wondering how the following code could be used to implement a tree. Also, what would be the most efficient way to keep a track of parent nodes? delegate void TreeVisitor<T>(T nodeData); class NTree<T> { T data; LinkedList<NTree<T>> children; public NTree(T data) { this.data = data; children = new LinkedList<NTree<T>>(); } public void addChild(T data) { children.AddFirst(new NTree<T>(data)); } public NTree<T> getChild(int i) { foreach (NTree<T> n in children) if (--i == 0) return n; return null; } public void traverse(NTree<T> node, TreeVisitor<T> visitor) { visitor(node.data); foreach (NTree<T> kid in node.children) traverse(kid, visitor); } }

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  • How to use delegate to perform callback between caller and web service helper class?

    - by codemonkie
    I have 2 classes A and B, where they belongs to the same namespace but resides in seperate files namely a.cs and b.cs, where class B essentially is a helper wrapping a web service call as follow: public class A { public A() // constructor { protected static B b = new B(); } private void processResult1(string result) { // come here when result is successful } private void processResult2(string result) { // come here when result is failed } static void main() { b.DoJobHelper(...); } } public class B { private com.nowhere.somewebservice ws; public B() { this.ws = new com.nowhere.somewebservice(); ws.JobCompleted += new JobCompletedEventHandler(OnCompleted); } void OnCompleted(object sender, JobCompletedEventArgs e) { string s = e.Result; Guid taskID = (Guid)e.UserState; switch (s) { case "Success": // Call processResult1(); break; case "Failed": // Call processResult2(); break; default: break; } } public void DoJobHelper() { Object userState = Guid.NewGuid(); ws.DoJob(..., userState); } } (1) I have seen texts on the net on using delegates for callbacks but failed to apply that to my case. All I want to do is to call the appropriate processResult() method upon OnCompleted() event, but dunno how to and where to declare the delegate: public delegate void CallBack(string s); (2) There is a sender object passed in to OnCompleted() but never used, did I miss anything there? Or how can I make good use of sender? Any helps appreciated.

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  • How can I get this dynamic WHERE statement in my LINQ-to-XML to work?

    - by Edward Tanguay
    In this question Jon Skeet offered a very interesting solution to making a LINQ-to-XML statement dynamic, but my knowledge of lambdas and delegates is not yet advanced enough to implement it: I've got it this far, but of course I get the error "smartForm does not exist in the current context": private void LoadWithId(int id) { XDocument xmlDoc = null; try { xmlDoc = XDocument.Load(FullXmlDataStorePathAndFileName); } catch (Exception ex) { throw new Exception(String.Format("Cannot load XML file: {0}", ex.Message)); } Func<XElement, bool> whereClause = (int)smartForm.Element("id") == id"; var smartForms = xmlDoc.Descendants("smartForm") .Where(whereClause) .Select(smartForm => new SmartForm { Id = (int)smartForm.Element("id"), WhenCreated = (DateTime)smartForm.Element("whenCreated"), ItemOwner = smartForm.Element("itemOwner").Value, PublishStatus = smartForm.Element("publishStatus").Value, CorrectionOfId = (int)smartForm.Element("correctionOfId"), IdCode = smartForm.Element("idCode").Value, Title = smartForm.Element("title").Value, Description = smartForm.Element("description").Value, LabelWidth = (int)smartForm.Element("labelWidth") }); foreach (SmartForm smartForm in smartForms) { _collection.Add(smartForm); } } Ideally I want to be able to just say: var smartForms = GetSmartForms(smartForm=> (int) smartForm.Element("DisplayOrder").Value > 50); I've got it this far, but I'm just not grokking the lambda magic, how do I do this? public List<SmartForm> GetSmartForms(XDocument xmlDoc, XElement whereClause) { var smartForms = xmlDoc.Descendants("smartForm") .Where(whereClause) .Select(smartForm => new SmartForm { Id = (int)smartForm.Element("id"), WhenCreated = (DateTime)smartForm.Element("whenCreated"), ItemOwner = smartForm.Element("itemOwner").Value, PublishStatus = smartForm.Element("publishStatus").Value, CorrectionOfId = (int)smartForm.Element("correctionOfId"), IdCode = smartForm.Element("idCode").Value, Title = smartForm.Element("title").Value, Description = smartForm.Element("description").Value, LabelWidth = (int)smartForm.Element("labelWidth") }); }

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  • XML comments on delegate declared events

    - by Matt Whitfield
    I am visiting some old code, and there are quite a few events declared with delegates manually rather than using EventHandler<T>, like this: /// <summary> /// Delegate for event Added /// </summary> /// <param name="index">Index of the item</param> /// <param name="item">The item itself</param> public delegate void ItemAdded(int index, T item); /// <summary> /// Added is raised whenever an item is added to the collection /// </summary> public event ItemAdded Added; All well and good, until I come to use sandcastle to document the library, because it then can't find any XML comments for the private Added field that is generated by the event declaration. I want to try and sort that out, but what I would like to do is either: Get sandcastle to ignore the auto-generated private field without telling it to ignore all private fields entirely or Get XML comments generated for the private field Is there any way of achieving this without re-factoring the code to look like this: /// <summary> /// Delegate for event <see cref="Added"/> /// </summary> /// <param name="index">Index of the item</param> /// <param name="item">The item itself</param> public delegate void ItemAdded(int index, T item); /// <summary> /// Private storage for the event firing delegate for the <see cref="Added"/> event /// </summary> private ItemAdded _added; /// <summary> /// Added is raised whenever an item is added to the collection /// </summary> public event ItemAdded Added { add { _added += value; } remove { _added -= value; } }

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  • [C#] How to use delegate to perform callback between caller and web service helper class?

    - by codemonkie
    I have 2 classes A and B, where they belongs to the same namespace but resides in seperate files namely a.cs and b.cs, where class B essentially is a helper wrapping a web service call as follow: public class A { public A() // constructor { protected static B b = new B(); } private void processResult1(string result) { // come here when result is successful } private void processResult2(string result) { // come here when result is failed } static void main() { b.DoJobHelper(...); } } public class B { private com.nowhere.somewebservice ws; public B() { this.ws = new com.nowhere.somewebservice(); ws.JobCompleted += new JobCompletedEventHandler(OnCompleted); } void OnCompleted(object sender, JobCompletedEventArgs e) { string s; Guid taskID = (Guid)e.UserState; switch (s) { case "Success": // Call processResult1(); break; case "Failed": // Call processResult2(); break; default: break; } } public void DoJobHelper() { Object userState = Guid.NewGuid(); ws.DoJob(..., userState); } } (1) I have seen texts on the net on using delegates for callbacks but failed to apply that to my case. All I want to do is to call the appropriate processResult() method upon OnCompleted() event, but dunno how to and where to declare the delegate: public delegate void CallBack(string s); (2) There is a sender object passed in to OnCompleted() but never used, did I miss anything there? Or how can I make good use of sender? Any helps appreciated.

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  • Pass Result of ASIHTTPRequest "requestFinished" Back to Originating Method

    - by Intelekshual
    I have a method (getAllTeams:) that initiates an HTTP request using the ASIHTTPRequest library. NSURL *httpURL = [[[NSURL alloc] initWithString:@"/api/teams" relativeToURL:webServiceURL] autorelease]; ASIHTTPRequest *request = [[[ASIHTTPRequest alloc] initWithURL:httpURL] autorelease]; [request setDelegate:self]; [request startAsynchronous]; What I'd like to be able to do is call [WebService getAllTeams] and have it return the results in an NSArray. At the moment, getAllTeams doesn't return anything because the HTTP response is evaluated in the requestFinished: method. Ideally I'd want to be able to call [WebService getAllTeams], wait for the response, and dump it into an NSArray. I don't want to create properties because this is disposable class (meaning it doesn't store any values, just retrieves values), and multiple methods are going to be using the same requestFinished (all of them returning an array). I've read up a bit on delegates, and NSNotifications, but I'm not sure if either of them are the best approach. I found this snippet about implementing callbacks by passing a selector as a parameter, but it didn't pan out (since requestFinished fires independently). Any suggestions? I'd appreciate even just to be pointed in the right direction. NSArray *teams = [[WebService alloc] getAllTeams]; (currently doesn't work, because getAllTeams doesn't return anything, but requestFinished does. I want to get the result of requestFinished and pass it back to getAllTeams:)

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  • Unit testing that an event is raised in C#, using reflection

    - by Thomas
    I want to test that setting a certain property (or more generally, executing some code) raises a certain event on my object. In that respect my problem is similar to http://stackoverflow.com/questions/248989/unit-testing-that-an-event-is-raised-in-c, but I need a lot of these tests and I hate boilerplate. So I'm looking for a more general solution, using reflection. Ideally, I would like to do something like this: [TestMethod] public void TestWidth() { MyClass myObject = new MyClass(); AssertRaisesEvent(() => { myObject.Width = 42; }, myObject, "WidthChanged"); } For the implementation of the AssertRaisesEvent, I've come this far: private void AssertRaisesEvent(Action action, object obj, string eventName) { EventInfo eventInfo = obj.GetType().GetEvent(eventName); int raisedCount = 0; Action incrementer = () => { ++raisedCount; }; Delegate handler = /* what goes here? */; eventInfo.AddEventHandler(obj, handler); action.Invoke(); eventInfo.RemoveEventHandler(obj, handler); Assert.AreEqual(1, raisedCount); } As you can see, my problem lies in creating a Delegate of the appropriate type for this event. The delegate should do nothing except invoke incrementer. Because of all the syntactic syrup in C#, my notion of how delegates and events really work is a bit hazy. How to do this?

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  • Using Interface Builder efficiently

    - by Aaron Wetzler
    I am new to iPhone and objective c. I have spent hours and hours and hours reading documents and trying to understand how things work. I have RTFM or at least am in the process. My main problem is that I want to understand how to specify where an event gets passed to and the only way I have been able to do it is by specifying delegates but I am certain there is an easier/quicker way in IB. So, an example. Lets say I have 20 different views and view controllers and one MyAppDelegate. I want to be able to build all of these different Xib files in IB and add however many buttons and text fields and whatever and then specify that they all produce some event in the MyAppDelegate object. To do this I added a MyAppDelegate object in each view controller in IB's list view. Then I created an IBAction method in MyAppDelegate in XCode and went back to IB and linked all of the events to the MyAppDelegate object in each Xib file. However when I tried running it it just crashed with a bad read exception. My guess is that each Xib file is putting a MyAppDelegate object pointer that has nothing to do with the eventual MyAppDelegate adress that will actually be created at runtime. So my question is...how can I do this?!!!

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  • asp.net vb user control raising an event on the calling page

    - by jvcoach23
    i'm trying to learn about user controls. I created a user control that has a textbox and a button. What i'd like to be able to do is when i click the button in the user control, populate a label in the aspx page. I understand that i could just have a button on the page that uses some properties on the user control to get that information.. but i'd like to know how to do it with the button the user control.. the reason for this is the button is just an example.. a learning tool. if i can get this working, i'd likely be putting thing in the user control that might require this kind of passing information. Anyway.. i've found some c# examples that i tried to get working as vb.. but once started getting into the delegates and events.. well.. it made me turn to this post. anyway.. hopefully someone can lend a hand.

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  • Visitor Pattern can be replaced with Callback functions?

    - by getit
    Is there any significant benefit to using either technique? In case there are variations, the Visitor Pattern I mean is this: http://en.wikipedia.org/wiki/Visitor_pattern And below is an example of using a delegate to achieve the same effect (at least I think it is the same) Say there is a collection of nested elements: Schools contain Departments which contain Students Instead of using the Visitor pattern to perform something on each collection item, why not use a simple callback (Action delegate in C#) Say something like this class Department { List Students; } class School { List Departments; VisitStudents(Action<Student> actionDelegate) { foreach(var dep in this.Departments) { foreach(var stu in dep.Students) { actionDelegate(stu); } } } } School A = new School(); ...//populate collections A.Visit((student)=> { ...Do Something with student... }); *EDIT Example with delegate accepting multiple params Say I wanted to pass both the student and department, I could modify the Action definition like so: Action class School { List Departments; VisitStudents(Action<Student, Department> actionDelegate, Action<Department> d2) { foreach(var dep in this.Departments) { d2(dep); //This performs a different process. //Using Visitor pattern would avoid having to keep adding new delegates. //This looks like the main benefit so far foreach(var stu in dep.Students) { actionDelegate(stu, dep); } } } }

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  • Starting an STA thread, but with parameters to the final function

    - by DRapp
    I'm a bit weak on how some delegates behave, such as passing a method as the parameter to be invoked. While trying to do some NUnit test scripts, I have something that I need to run many test with. Each of these tests requires a GUI created and thus the need for an STA thread. So, I have something like public class MyTest { // the Delegate "ThreadStart" is part of the System.Threading namespace and is defined as // public delegate void ThreadStart(); protected void Start_STA_Thread(ThreadStart whichMethod) { Thread thread = new Thread(whichMethod); thread.SetApartmentState(ApartmentState.STA); //Set the thread to STA thread.Start(); thread.Join(); } [Test] public void Test101() { // Since the thread issues an INVOKE of a method, I'm having it call the // corresponding "FromSTAThread" method, such as Start_STA_Thread( Test101FromSTAThread ); } protected void Test101FromSTAThread() { MySTA_RequiredClass oTmp = new MySTA_RequiredClass(); Assert.IsTrue( oTmp.DoSomething() ); } } This part all works fine... Now the next step. I now have a different set of tests that ALSO require an STA thread. However, each "thing" I need to do requires two parameters... both strings (for this case). How do I go about declaring proper delegate so I can pass in the method I need to invoke, AND the two string parameters in one shot... I may have 20+ tests to run with in this pattern and may have future of other similar tests with different parameter counts and types of parameters too. Thanks.

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  • Performance - FunctionCall vs Event vs Action vs Delegate

    - by hwcverwe
    Currently I am using Microsoft Sync Framework to synchronize databases. I need to gather information per record which is inserted/updated/deleted by Microsoft Sync Framework and do something with this information. The sync speed can go over 50.000 records per minute. So that means my additional code need to be very lightweight otherwise it will be a huge performance penalty. Microsoft Sync Framework raises an SyncProgress event for each record. I am subscribed to that code like this: // Assembly1 SyncProvider.SyncProgress += OnSyncProgress; // .... private void OnSyncProgress(object sender, DbSyncProgressEventArgs e) { switch (args.Stage) { case DbSyncStage.ApplyingInserts: // MethodCall/Delegate/Action<>/EventHandler<> => HandleInsertedRecordInformation // Do something with inserted record info break; case DbSyncStage.ApplyingUpdates: // MethodCall/Delegate/Action<>/EventHandler<> => HandleUpdatedRecordInformation // Do something with updated record info break; case DbSyncStage.ApplyingDeletes: // MethodCall/Delegate/Action<>/EventHandler<> => HandleDeletedRecordInformation // Do something with deleted record info break; } } Somewhere else in another assembly I have three methods: // Assembly2 public class SyncInformation { public void HandleInsertedRecordInformation(...) {...} public void HandleUpdatedRecordInformation(...) {...} public void HandleInsertedRecordInformation(...) {...} } Assembly2 has a reference to Assembly1. So Assembly1 does not know anything about the existence of the SyncInformation class which need to handle the gathered information. So I have the following options to trigger this code: use events and subscribe on it in Assembly2 1.1. EventHandler< 1.2. Action< 1.3. Delegates using dependency injection: public class Assembly2.SyncInformation : Assembly1.ISyncInformation Other? I know the performance depends on: OnSyncProgress switch using a method call, delegate, Action< or EventHandler< Implementation of SyncInformation class I currently don't care about the implementation of the SyncInformation class. I am mainly focused on the OnSyncProgress method and how to call the SyncInformation methods. So my questions are: What is the most efficient approach? What is the most in-efficient approach? Is there a better way than using a switch in OnSyncProgress?

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  • UITableView crashes when trying to scroll

    - by Ondrej
    Hi, I have a problem with data in UITableView. I have UIViewController, that contains UITableView outlet and few more things I am using and ... It works :) ... it works lovely, but ... I've created an RSS reader class that is using delegates to deploy the data to the table ... and once again, If I'll just create dummy data in the main controller everything works! problem is with this line: rss.delegate = self; Preview looks a little bit broken than here are those RSS reader files on Google code: (Link to the header file on GoogleCode) (Link to the implementation file on Google code) viewDidLoad function of my controller: IGDataRss20 *rss = [[[IGDataRss20 alloc] init] autorelease]; rss.delegate = self; [rss initWithContentsOfUrl:@"http://rss.cnn.com/rss/cnn_topstories.rss"]; and my delegate methods: - (void)parsingEnded:(NSArray *)result { super.data = [[NSMutableArray alloc] initWithArray:result]; NSLog(@"My Items: %d", [super.data count]); [super.table reloadData]; NSLog(@"Parsing ended"); } (void)parsingError:(NSString *)message { NSLog(@"MyMessage: %@", message); } (void)parsingStarted:(NSXMLParser *)parser { NSLog(@"Parsing started"); } Just to clarify, NSLog(@"Parsing ended"); is being executed and I have 10 items in the array. Ok, here's my RSS reader header file: @class IGDataRss20; @protocol IGDataRss20Delegate @optional (void)parsingStarted:(NSXMLParser *)parser; (void)parsingError:(NSString *)message; (void)parsingEnded:(NSArray *)result; @end @interface IGDataRss20 : NSObject { NSXMLParser *rssParser; NSMutableArray *data; NSMutableDictionary *currentItem; NSString *currentElement; id <IGDataRss20Delegate> delegate; } @property (nonatomic, retain) NSMutableArray *data; @property (nonatomic, assign) id delegate; (void)initWithContentsOfUrl:(NSString *)rssUrl; (void)initWithContentsOfData:(NSData *)inputData; @end And this RSS reader implementation file: #import "IGDataRss20.h" @implementation IGDataRss20 @synthesize data, delegate; (void)initWithContentsOfUrl:(NSString *)rssUrl { self.data = [[NSMutableArray alloc] init]; NSURL *xmlURL = [NSURL URLWithString:rssUrl]; rssParser = [[NSXMLParser alloc] initWithContentsOfURL:xmlURL]; [rssParser setDelegate:self]; [rssParser setShouldProcessNamespaces:NO]; [rssParser setShouldReportNamespacePrefixes:NO]; [rssParser setShouldResolveExternalEntities:NO]; [rssParser parse]; } (void)initWithContentsOfData:(NSData *)inputData { self.data = [[NSMutableArray alloc] init]; rssParser = [[NSXMLParser alloc] initWithData:inputData]; [rssParser setDelegate:self]; [rssParser setShouldProcessNamespaces:NO]; [rssParser setShouldReportNamespacePrefixes:NO]; [rssParser setShouldResolveExternalEntities:NO]; [rssParser parse]; } (void)parserDidStartDocument:(NSXMLParser *)parser { [[self delegate] parsingStarted:parser]; } (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError { NSString * errorString = [NSString stringWithFormat:@"Unable to parse RSS feed (Error code %i )", [parseError code]]; NSLog(@"Error parsing XML: %@", errorString); if ([parseError code] == 31) NSLog(@"Error code 31 is usually caused by encoding problem."); [[self delegate] parsingError:errorString]; } (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict { currentElement = [elementName copy]; if ([elementName isEqualToString:@"item"]) currentItem = [[NSMutableDictionary alloc] init]; } (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName { if ([elementName isEqualToString:@"item"]) { [data addObject:(NSDictionary *)[currentItem copy]]; } } (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string { if (![currentItem objectForKey:currentElement]) [currentItem setObject:[[[NSMutableString alloc] init] autorelease] forKey:currentElement]; [[currentItem objectForKey:currentElement] appendString:string]; } (void)parserDidEndDocument:(NSXMLParser *)parser { //NSLog(@"RSS array has %d items: %@", [data count], data); [[self delegate] parsingEnded:(NSArray *)self.data]; } (void)dealloc { [data, delegate release]; [super dealloc]; } @end Hope someone will be able to help me as I am becoming to be quite desperate, and I thought I am not already such a greenhorn :) Thanks, Ondrej

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  • The sign of a true manager is delegation (C# style)

    - by MarkPearl
    Today I thought I would write a bit about delegates in C#. Up till recently I have managed to side step any real understanding of what delegates do and why they are useful – I mean, I know roughly what they do and have used them a lot, but I have never really got down dirty with them and mucked about. Recently however with my renewed interest in Silverlight delegates came up again as a possible solution to a particular problem, and suddenly I found myself opening a bland little console application to just see exactly how far I could take delegates with my limited knowledge. So, let’s first look at the MSDN definition of delegates… A delegate declaration defines a reference type that can be used to encapsulate a method with a specific signature. A delegate instance encapsulates a static or an instance method. Delegates are roughly similar to function pointers in C++; however, delegates are type-safe and secure. Well, don’t you love MSDN for such a useful definition. I must give it credit though… later on it really explains it a bit better by saying “A delegate lets you pass a function as a parameter. The type safety of delegates requires the function you pass as a delegate to have the same signature as the delegate declaration.” A little more reading up on delegates mentions that delegates are similar to interfaces in that they enable the separation of specification and implementation. A delegate declares a single method, while an interface declares a group of methods. So enough reading - lets look at some code and see a basic example of a delegate… Let’s assume we have a console application with a simple delegate declared called AdjustValue like below… class Program { private delegate int AdjustValue(int val); static void Main(string[] args) { } } In a sense, all we have said is that we will be creating one or more methods that follow the same pattern as AdjustValue – i.e. they will take one input value of type int and return an integer. We could then expand our code to have various methods that match the structure of our delegate AdjustValue (remember the structure is int xxx (int xxx)) class Program { private delegate int AdjustValue(int val); private static int Dbl(int val) { return val * 2; } private static int AlwaysOne(int val) { return 1; } static void Main(string[] args) { } }  Above I have expanded my project to have two methods, one called Dbl and the other AlwaysOne. Dbl always returns double the input val and AlwaysOne always returns 1. I could now declare a variable and assign it to be one of those functions, like the following… class Program { private delegate int AdjustValue(int val); private static int Dbl(int val) { return val * 2; } private static int AlwaysOne(int val) { return 1; } static void Main(string[] args) { AdjustValue myDelegate; myDelegate = Dbl; Console.WriteLine(myDelegate(1).ToString()); Console.ReadLine(); } } In this instance I have declared an instance of the AdjustValue delegate called myDelegate; I have then told myDelegate to point to the method Dbl, and then called myDelegate(1). What would the result be? Yes, in this instance it would be exactly the same as me calling the following code… static void Main(string[] args) { Console.WriteLine(Dbl(1).ToString()); Console.ReadLine(); }   So why all the extra work for delegates when we could just do what we did above and call the method directly? Well… that separation of specification to implementation comes to mind. So, this all seems pretty simple. Let’s take a slightly more complicated variation to the console application. Assume that my project is the same as the one previously except that my main method is adjusted as follows… static void Main(string[] args) { AdjustValue myDelegate; myDelegate = Dbl; myDelegate = AlwaysOne; Console.WriteLine(myDelegate(1).ToString()); Console.ReadLine(); } What would happen in this scenario? Quite simply “1” would be written to the console, the reason being that myDelegate was last pointing to the AlwaysOne method before it was called. Make sense? In a way, the myDelegate is a variable method that can be swapped and changed when needed. Let’s make the code a little more confusing by using a delegate in the declaration of another delegate as shown below… class Program { private delegate int AdjustValue(InputValue val); private delegate int InputValue(); private static int Dbl(InputValue val) { return val()*2; } private static int GetInputVal() { Console.WriteLine("Enter a whole number : "); return Convert.ToInt32(Console.ReadLine()); } static void Main(string[] args) { AdjustValue myDelegate; myDelegate = Dbl; Console.WriteLine(myDelegate(GetInputVal).ToString()); Console.ReadLine(); } }   Now it gets really interesting because it looks like we have passed a method into a function in the main method by declaring… Console.WriteLine(myDelegate(GetInputVal).ToString()); So, what it the output? Well, try take a guess on what will happen – then copy the code and see if you got it right. Well that brings me to the end of this short explanation of Delegates. Hopefully it made sense!

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  • C# Func delegate with params type

    - by Sarah Vessels
    How, in C#, do I have a Func parameter representing a method with this signature? XmlNode createSection(XmlDocument doc, params XmlNode[] childNodes) I tried having a parameter of type Func<XmlDocument, params XmlNode[], XmlNode> but, ooh, ReSharper/Visual Studio 2008 go crazy highlighting that in red.

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  • How set EnqueueCallBack to my generic callback

    - by CrazyJoe
    using System; using System.Windows; using System.Windows.Controls; using System.Windows.Documents; using System.Windows.Ink; using System.Windows.Input; using System.Windows.Media; using System.Windows.Media.Animation; using System.Windows.Shapes; using Microsistec.Domain; using Microsistec.Client; using Microsoft.VisualStudio.TestTools.UnitTesting; using System.Collections.Generic; using Microsistec.Tools; using System.Json; using Microsistec.SystemConfig; using System.Threading; using Microsoft.Silverlight.Testing; namespace Test { [TestClass] public class SampleTest : SilverlightTest { [TestMethod, Asynchronous] public void login() { List<PostData> data = new List<PostData>(); data.Add(new PostData("email", "xxx")); data.Add(new PostData("password", MD5.GetHashString("xxx"))); WebClient.sendData(Config.DataServerURL + "/user/login", data, LoginCallBack); EnqueueCallback(?????????); EnqueueTestComplete(); } [Asynchronous] public void LoginCallBack(object sender, System.Net.UploadStringCompletedEventArgs e) { string json = Microsistec.Client.WebClient.ProcessResult(e); var result = JsonArray.Parse(json); Assert.Equals("1", result["value"].ToString()); TestComplete(); } } Im tring to set ???????? value but my callback is generic, it is setup on my WebClient .SendData, how i implement my EnqueueCallback to a my already functio LoginCallBack???

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  • UIScrollView imageViewDidEndZooming not being called

    - by Jorge
    I have this subclass of UIScrollView: @interface MyScrollView : UIScrollView <UIScrollViewDelegate> And I have those delegate methods - (void)scrollViewDidEndZooming:(UIScrollView *)aScrollView withView:(UIView *)view atScale(float)aScale{ NSLog(@"zoomed"); } - (UIView *)viewForZoomingInScrollView:(UIScrollView *)aScrollView{ NSLog(@"willzoom"); } When I zoom in MyScrollView viewForZoomingInScrollView is called but scrollViewDidEndZooming never gets called. Any idea why??

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  • No visible @interface for 'AppDelegate' declares the selector

    - by coolhongly
    I'm now writing a registration screen before my tabBar shows up. My idea is to show my registration screen through this method (no dismiss function for now): - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { // Override point for customization after application launch. Register *registerView = [[Register alloc] initWithNibName:nil bundle:nil]; [self presentModalViewController:registerView animated:YES]; return YES; } Which is in AppDelegate.m Unfortunately it doesn't work. Could you help me solve this please?

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  • Translating delegate usage from C# to VB

    - by Homeliss
    ContactManager.PostSolve += PostSolve; I am having a problem converting this piece of code from C# to VB.NET. ContactManager.PostSolve is a delegate. I tried the following but it doesn't work, it says PostSolve is not an event of ContactManager: AddHandler ContactManager.PostSolve, AddressOf PostSolve The following works, but this only allows me to have one handler for the delegate: ContactManager.PostSolve = new PostSolveDelegate(AddressOf PostSolve) Is there a way for me to do the same thing in VB that was done in the first piece of code? Thanks!

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  • Delegate, BeginInvoke. EndInvoke - How to clean up multiple Async threat calls to the same delegate?

    - by Dan
    I've created a Delegate that I intend to call Async. Module Level Delegate Sub GetPartListDataFromServer(ByVal dvOriginal As DataView, ByVal ProgramID As Integer) Dim dlgGetPartList As GetPartListDataFromServer The following code I use in a method Dim dlgGetPartList As New GetPartListDataFromServer(AddressOf AsyncThreadMethod_GetPartListDataFromServer) dlgGetPartList.BeginInvoke(ucboPart.DataSource, ucboProgram.Value, AddressOf AsyncCallback_GetPartListDataFromServer, Nothing) The method runs and does what it needs to The Asyn callback is fired upon completion where I do an EndInvoke Sub AsyncCallback_GetPartListDataFromServer(ByVal ar As IAsyncResult) dlgGetPartList.EndInvoke(Nothing) End Sub It works as long as the method that starts the BeginInvoke on the delegate only ever runs while there is not a BeginInvoke/Thread operation already running. Problem is that the a new thread could be invoked while another thread on the delegate is still running and hasnt yet been EndInvoke'd. The program needs to be able to have the delegate run in more than one instance at a time if necessary and they all need to complete and have EndInvoke called. Once I start another BeginInvoke I lose the reference to the first BeginInvoke so I am unable to clean up the new thread with an EndInvoke. What is a clean solution and best practice to overcome this problem?

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  • Become UIScrollViewDelegate delegate for UITableView

    - by Brian
    I have a UITableView instance variable. I want to be able to register my view controller to be the UIScrollViewDelegate for my UITableView controller. I have already tried tableView.delegate = self; But when scrolling, my methods - (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView - (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate don't get called. Any suggestions?

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  • C#: WebBrowser.Navigated Only Fires when I MessageBox.Show();

    - by tsilb
    I have a WebBrowser control which is being instantiated dynamically from a background STA thread because the parent thread is a BackgroundWorker and has lots of other things to do. The problem is that the Navigated event never fires, unless I pop a MessageBox.Show() in the method that told it to .Navigate(). I shall explain: ThreadStart ts = new ThreadStart(GetLandingPageContent_ChildThread); Thread t = new Thread(ts); t.SetApartmentState(ApartmentState.STA); t.Name = "Mailbox Processor"; t.Start(); protected void GetLandingPageContent_ChildThread() { WebBrowser wb = new WebBrowser(); wb.Navigated += new WebBrowserNavigatedEventHandler(wb_Navigated); wb.Navigate(_url); MessageBox.Show("W00t"); } protected void wb_Navigated(object sender, WebBrowserNavigatedEventArgs e) { WebBrowser wb = (WebBrowser)sender; // Breakpoint HtmlDocument hDoc = wb.Document; } This works fine; but the messagebox will get in the way since this is an automation app. When I remove the MessageBox.Show(), the WebBrowser.Navigated event never fires. I've tried supplanting this line with a Thread.Sleep(), and by suspending the parent thread. Once I get this out of the way, I intend to Suspend the parent thread while the WebBrowser is doing its job and find some way of passing the resulting HTML back to the parent thread so it can continue with further logic. Why does it do this? How can I fix it? If someone can provide me with a way to fetch the content of a web page, fill out some data, and return the content of the page on the other side of the submit button, all against a webserver that doesn't support POST verbs nor passing data via QueryString, I'll also accept that answer as this whole exercise will have been unneccessary.

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