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  • What was your "aha moment" in understanding delegates?

    - by CM90
    Considering the use of delegates in C#, does anyone know if there is a performance advantage or if it is a convenience to the programmer? If we are creating an object that holds a method, it sounds as if that object would be a constant in memory to be called on, instead of loading the method every time it is called. For example, if we look at the following Unity3D-based code: public delegate H MixedTypeDelegate<G, H>(G g) public class MainParent : MonoBehaviour // Most Unity classes inherit from M.B. { public static Vector3 getPosition(GameObject g) { /* GameObject is a Unity class, and Vector3 is a struct from M.B. The "position" component of a GameObject is a Vector3. This method takes the GameObject I pass to it & returns its position. */ return g.transform.position; } public static MixedTypeDelegate<GameObject, Vector3> PositionOf; void Awake( ) // Awake is the first method called in Unity, always. { PositionOf = MixedTypeDelegate<GameObject, Vector3>(getPosition); } } public class GameScript : MainParent { GameObject g = new GameObject( ); Vector3 whereAmI; void Update( ) { // Now I can say: whereAmI = PositionOf(g); // Instead of: whereAmI = getPosition(g); } } . . . But that seems like an extra step - unless there's that extra little thing that it helps. I suppose the most succinct way to ask a second question would be to say: When you had your aha moment in understanding delegates, what was the context/scenario/source? Thank you!

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  • Prevent anonymous access to form and application pages in SharePoint 2010

    - by shehan
    When you create a Publishing site that has anonymous access enabled, you will notice that anonymous users will not be able to access pages that reside in the “_layouts” virtual directory (e.g. http://siteX/_layouts/viewlsts.aspx). This is because the publishing infrastructure activates a hidden feature that prevents anonymous users from accessing these types of pages. However, if you were to create a site collection based of  Blank Site Template, you would notice that these pages are accessible by anonymous users. The fix is quite simple. There is a hidden feature that you would need to manually activate via stsadm. The feature is called “ViewFormPagesLockDown” (and is available in the Features folders in the 14 hive) To activate it: stsadm -o activatefeature -filename ViewFormPagesLockDown\feature.xml -url http://ServerName Once activated anonymous users will be promoted to enter credentials when they try to access form and application pages. The feature can also be deactivated for publishing sites that have it automatically turned on.   Technorati Tags: SharePoint 2010,anonymous,lockdown,pages,security

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  • Delegates and ParamArray - Workaround Suggestions?

    - by M.A. Hanin
    Some predefined methods contain a ParamArray in their signature. Delegates, however, cannot contain a ParamArray in their signature. Main question: Assume you wish to create a delegation mechanism for a specific method which requires a ParamArray. How would you work around this constraint? "Bonus" question: Assume you wish to create a generalized delegation mechanism for all methods which require ParamArray, how would you do that?

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  • Please Explain .NET Delegates

    - by user275561
    So I read MSDN and Stack Overflow. I understand what the Action Delegate does in general but it is not clicking no matter how many examples I do. In general, the same goes for the idea of delegates. So here is my question. When you have a function like this: public GetCustomers(Action<IEnumerable<Customer>,Exception> callBack) { } What is this, and what should I pass to it?

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  • Using Delegates in C# (Part 1)

    - by rajbk
    This post provides a very basic introduction of delegates in C#. Part 2 of this post can be read here. A delegate is a class that is derived from System.Delegate.  It contains a list of one or more methods called an invocation list. When a delegate instance is “invoked” with the arguments as defined in the signature of the delegate, each of the methods in the invocation list gets invoked with the arguments. The code below shows example with static and instance methods respectively: Static Methods 1: using System; 2: using System.Linq; 3: using System.Collections.Generic; 4: 5: public delegate void SayName(string name); 6: 7: public class Program 8: { 9: [STAThread] 10: static void Main(string[] args) 11: { 12: SayName englishDelegate = new SayName(SayNameInEnglish); 13: SayName frenchDelegate = new SayName(SayNameInFrench); 14: SayName combinedDelegate =(SayName)Delegate.Combine(englishDelegate, frenchDelegate); 15: 16: combinedDelegate.Invoke("Tom"); 17: Console.ReadLine(); 18: } 19: 20: static void SayNameInFrench(string name) { 21: Console.WriteLine("J'ai m'appelle " + name); 22: } 23: 24: static void SayNameInEnglish(string name) { 25: Console.WriteLine("My name is " + name); 26: } 27: } We have declared a delegate of type SayName with return type of void and taking an input parameter of name of type string. On line 12, we create a new instance of this delegate which refers to a static method - SayNameInEnglish.  SayNameInEnglish has the same return type and parameter list as the delegate declaration.  Once a delegate is instantiated, the instance will always refer to the same target. Delegates are immutable. On line 13, we create a new instance of the delegate but point to a different static method. As you may recall, a delegate instance encapsulates an invocation list. You create an invocation list by combining delegates using the Delegate.Combine method (there is an easier syntax as you will see later). When two non null delegate instances are combined, their invocation lists get combined to form a new invocation list. This is done in line 14.  On line 16, we invoke the delegate with the Invoke method and pass in the required string parameter. Since the delegate has an invocation list with two entries, each of the method in the invocation list is invoked. If an unhandled exception occurs during the invocation of one of these methods, the exception gets bubbled up to the line where the invocation was made (line 16). If a delegate is null and you try to invoke it, you will get a System.NullReferenceException. We see the following output when the method is run: My name is TomJ'ai m'apelle Tom Instance Methods The code below outputs the same results as before. The only difference here is we are creating delegates that point to a target object (an instance of Translator) and instance methods which have the same signature as the delegate type. The target object can never be null. We also use the short cut syntax += to combine the delegates instead of Delegate.Combine. 1: public delegate void SayName(string name); 2: 3: public class Program 4: { 5: [STAThread] 6: static void Main(string[] args) 7: { 8: Translator translator = new Translator(); 9: SayName combinedDelegate = new SayName(translator.SayNameInEnglish); 10: combinedDelegate += new SayName(translator.SayNameInFrench); 11:  12: combinedDelegate.Invoke("Tom"); 13: Console.ReadLine(); 14: } 15: } 16: 17: public class Translator { 18: public void SayNameInFrench(string name) { 19: Console.WriteLine("J'ai m'appelle " + name); 20: } 21: 22: public void SayNameInEnglish(string name) { 23: Console.WriteLine("My name is " + name); 24: } 25: } A delegate can be removed from a combination of delegates by using the –= operator. Removing a delegate from an empty list or removing a delegate that does not exist in a non empty list will not result in an exception. Delegates are invoked synchronously using the Invoke method. We can also invoke them asynchronously using the BeginInvoke and EndInvoke methods which are compiler generated.

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  • Are delegates copied during assignment to an event?

    - by Sir Psycho
    Hi, The following code seems to execute the FileRetrieved event more than once. I thought delegates were a reference type. I was expecting this to execute once. I'm going to take a guess and say that the reference is being passed by value, therefore copied but I don't like guesswork :-) public delegate void DirListEvent<T>(T dirItem); void Main() { DirListEvent<string> printFilename = s => { Console.WriteLine (s); }; var obj = new DirectoryLister(); obj.FileRetrieved += printFilename; obj.FileRetrieved += printFilename; obj.GetDirListing(); } public class DirectoryLister { public event DirListEvent<string> FileRetrieved; public DirectoryLister() { FileRetrieved += delegate {}; } public void GetDirListing() { foreach (var file in Directory.GetFiles(@"C:\")) { FileRetrieved(file); } } }

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  • Are static delegates thread-safe?

    - by leypascua
    Consider this code snippet: public static class ApplicationContext { private static Func<TService> Uninitialized<TService>() { throw new InvalidOperationException(); } public static Func<IAuthenticationProvider> AuthenticationProvider = Uninitialized<IAuthenticationProvider>(); public static Func<IUnitOfWorkFactory> UnitOfWorkFactory = Uninitialized<IUnitOfWorkFactory>(); } //can also be in global.asax if used in a web app. public static void Main(string[] args) { ApplicationContext.AuthenticationProvider = () => new LdapAuthenticationProvider(); ApplicationContext.UnitOfWorkFactory = () => new EFUnitOfWorkFactory(); } //somewhere in the code.. say an ASP.NET MVC controller ApplicationContext.AuthenticationProvider().SignIn(username, true); Are delegates in the static class ApplicationContext thread-safe in the sense that multiple-threads can invoke them? What potential problems will I face if I pursue this approach?

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  • c# Delegates, Events and Lambda Expr for new students

    - by MarkP
    I've been asked by my pointy haired boss to educate our new co-ops (interns) in the ways of C#. I have roughly ~30mins to cover the topics of Delegates, Events and Lambda Expressions. The time restriction is rather tight and the topics are broad. Since I'm not a C# guru, I would like some hints and pointers. Since my time is short, what points should I cover with respect to the three topics listed above? What are some good Do's and Dont's when using those three things? I might have time for a short Lambda Expr demo. What is the most common use of LExpr (probably a Select().Where() statement on an enumerable??) that I could demo? Thanks. EDIT: The students have working knowledge of C++ and Java.

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  • DNS down in Anonymous attack

    - by Tal Weiss
    As I'm writing this our company website and the web-service we developed are down in the big GoDaddy outage resulting from an Anonymous attack (or so says Twitter). We used GoDaddy as our registrar and we use it for DNS for some domains. Tomorrow is a new day - what can we do to mitigate such outages? Simply moving to, say, Route 53 for DNS might not be enough. Is there any way to remove this single point of failure?

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  • JS: variable inheritance in anonymous functions - scope

    - by tkSimon
    hey guys, someone from doctype sent me here. long story short: var o="before"; x = function() //this needs to be an anonymous function { alert(o); //the variable "o" is from the parent scope }; o="after"; //this chages "o" in the anonymous function x(); //this results in in alert("after"); //which is not the way i want/need it in reality my code is somewhat more complex. my script iterates through many html objects and adds an event listener each element. i do this by declaring an anonymous function for each element and call another function with an ID as argument. that ID is represented by the "o"-variable in this example. after some thinking i understand why it is the way it is, but is there a way to get js to evaluate o as i declare the anonymous function without dealing with the id attribute and fetching my ID from there? my full source code is here: http://pastebin.com/GMieerdw the anonymous function is on line 303

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  • Delegates in .NET: how are they constructed ?

    - by Saulius
    While inspecting delegates in C# and .NET in general, I noticed some interesting facts: Creating a delegate in C# creates a class derived from MulticastDelegate with a constructor: .method public hidebysig specialname rtspecialname instance void .ctor(object 'object', native int 'method') runtime managed { } Meaning that it expects the instance and a pointer to the method. Yet the syntax of constructing a delegate in C# suggests that it has a constructor new MyDelegate(int () target) where I can recognise int () as a function instance (int *target() would be a function pointer in C++). So obviously the C# compiler picks out the correct method from the method group defined by the function name and constructs the delegate. So the first question would be, where does the C# compiler (or Visual Studio, to be precise) pick this constructor signature from ? I did not notice any special attributes or something that would make a distinction. Is this some sort of compiler/visualstudio magic ? If not, is the T (args) target construction valid in C# ? I did not manage to get anything with it to compile, e.g.: int () target = MyMethod; is invalid, so is doing anything with MyMetod, e.g. calling .ToString() on it (well this does make some sense, since that is technically a method group, but I imagine it should be possible to explicitly pick out a method by casting, e.g. (int())MyFunction. So is all of this purely compiler magic ? Looking at the construction through reflector reveals yet another syntax: Func CS$1$0000 = new Func(null, (IntPtr) Foo); This is consistent with the disassembled constructor signature, yet this does not compile! One final interesting note is that the classes Delegate and MulticastDelegate have yet another sets of constructors: .method family hidebysig specialname rtspecialname instance void .ctor(class System.Type target, string 'method') cil managed Where does the transition from an instance and method pointer to a type and a string method name occur ? Can this be explained by the runtime managed keywords in the custom delegate constructor signature, i.e. does the runtime do it's job here ?

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  • Office documents prompt for login in anonymous SharePoint site

    - by xmt15
    I have a MOSS 07 site that is configured for anonymous access. There is a document library within this site that also has anonymous access enabled. When an anonymous user clicks on a PDF file in this library, he or she can read or download it with no problem. When a user clicks on an Office document, he or she is prompted with a login box. The user can cancel out of this box without entering a log in, and will be taken to the document. This happens in IE but not FireFox. I see some references to this question on the web but no clear solutions: http://www.microsoft.com/communities/newsgroups/en-us/default.aspx?dg=microsoft.public.sharepoint.windowsservices.development&tid=5452e093-a0d7-45c5-8ed0-96551e854cec&cat=en_US_CC8402B4-DC5E-652D-7DB2-0119AFB7C906&lang=en&cr=US&sloc=&p=1 http://www.sharepointu.com/forums/t/5779.aspx http://www.eggheadcafe.com/software/aspnet/30817418/anonymous-users-getting-p.aspx

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  • Invoke a subclass method of an anonymous class

    - by arjacsoh
    I am trying right now to dig into anonymous classes and one question was just arised I 'd prefer not to refer to much details and to pose my question straightforward: How can I invoke the method sizzle() in the following anonymous class: public class Popcorn { public void pop() { System.out.println("popcorn"); } } class Food { Popcorn p = new Popcorn() { public void sizzle() { System.out.println("anonymous sizzling popcorn"); } public void pop() { System.out.println("anonymous popcorn"); } }; public void popIt() { p.pop(); // OK, Popcorn has a pop() method p.sizzle(); // Not Legal! Popcorn does not have sizzle() } } It is known and definite in polymorphism rules that a refernce of a superclass cannot invoke methods of subclass without downcasting (even if it refers to an object of the given subclass). However in the above case what is the "key" to invoke the sizzle() method?

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  • Different behavior of reflected generic delegates with and without debugger

    - by Andrew_B
    Hello. We have encountered some strange things while calling reflected generic delegates. In some cases with attatched debuger we can make impossible call, while without debugger we cannot catch any exception and application fastfails. Here is the code: using System; using System.Windows.Forms; using System.Reflection; namespace GenericDelegate { public partial class Form1 : Form { public Form1() { InitializeComponent(); } private delegate Class2 Delegate1(); private void button1_Click(object sender, EventArgs e) { MethodInfo mi = typeof (Class1<>).GetMethod("GetClass", BindingFlags.NonPublic | BindingFlags.Static); if (mi != null) { Delegate1 del = (Delegate1) Delegate.CreateDelegate(typeof (Delegate1), mi); MessageBox.Show("1"); try { del(); } catch (Exception) { MessageBox.Show("No, I can`t catch it"); } MessageBox.Show("2"); mi.Invoke(null, new object[] {});//It's Ok, we'll get exception here MessageBox.Show("3"); } } class Class2 { } class Class1<T> : Class2 { internal static Class2 GetClass() { Type type = typeof(T); MessageBox.Show("Type name " + type.FullName +" Type: " + type + " Assembly " + type.Assembly); return new Class1<T>(); } } } } There are two problems: Behavior differs with debugger and without You cannot catch this error without debugger by clr tricks. It's just not the clr exception. There are memory acces vialation, reading zero pointer inside of internal code. Use case: You develop something like plugins system for your app. You read external assembly, find suitable method in some type, and execute it. And we just forgot about that we need to check up is the type generic or not. Under VS (and .net from 2.0 to 4.0) everything works fine. Called function does not uses static context of generic type and type parameters. But without VS application fails with no sound. We even cannot identify call stack attaching debuger. Tested with .net 4.0 The question is why VS catches but runtime do not?

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  • how to use anonymous generic delegate in C# 2.0

    - by matti
    Hi. I have a class called NTree: class NTree<T> { public NTree(T data) { this.data = data; children = new List<NTree<T>>(); _stopTraverse = false; } ... public void Traverse(NTree<T> node, TreeVisitor<T> visitor) { try { _stopTraverse = false; Traverse(node, visitor); } finally { _stopTraverse = false; } } private void TraverseInternal(NTree<T> node, TreeVisitor<T> visitor) { if (_stopTraverse) return; if (!visitor(node.data)) { _stopTraverse = true; } foreach (NTree<T> kid in node.children) Traverse(kid, visitor); } When I try to use Traverse with anonymous delegate I get: Argument '2': cannot convert from 'anonymous method' to 'NisConverter.TreeVisitor' The code: tTable srcTable = new tTable(); DataRow[] rows; rootTree.Traverse(rootTree, delegate(TableRows tr) { if (tr.TableName == srcTable.mappingname) { rows = tr.Rows; return false; } }); This however produces no errors: static bool TableFinder<TableRows>(TableRows tr) { return true; } ... rootTree.Traverse(rootTree, TableFinder); I have tried to put "arrowhead-parenthisis" and everything to anonymous delegate but it just does not work. Please help me! Thanks & BR -Matti

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  • Lambda expressions as CLR (.NET) delegates / event handlers in Visual C++ 2010

    - by absence
    Is it possible to use the new lambda expressions in Visual C++ 2010 as CLR event handlers? I've tried the following code: SomeEvent += gcnew EventHandler( [] (Object^ sender, EventArgs^ e) { // code here } ); It results in the following error message: error C3364: 'System::EventHandler' : invalid argument for delegate constructor; delegate target needs to be a pointer to a member function Am I attempting the impossible, or is simply my syntax wrong?

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  • Problem using delegates, static, and dependencyproperties

    - by red-X
    I'm trying to animate a private variable named radius, which works. However while its changing I'm trying to execute a function which is getting to be quite of a problem. the code i have is below, it wont run because it has the following error An object reference is required for the non-static field, method, or property 'AppPart.SetChildrenPosition()' specifically new SetChildrenPositionDelegate(SetChildrenPosition) this part in this sentance part.Dispatcher.BeginInvoke(new SetChildrenPositionDelegate(SetChildrenPosition), new Object()); thnx to anyone able to help me. class AppPart : Shape { public string name { get; set; } public List<AppPart> parts { get; set; } private double radius { get { return (double)GetValue(radiusProperty); } set { SetValue(radiusProperty, value); } } public static readonly DependencyProperty radiusProperty = DependencyProperty.Register( "radius", typeof(double), typeof(AppPart), new PropertyMetadata( new PropertyChangedCallback(radiusChangedCallback))); private delegate void SetChildrenPositionDelegate(); private void SetChildrenPosition() { //do something with radius } private static void radiusChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e) { AppPart part = d as AppPart; part.Dispatcher.BeginInvoke(new SetChildrenPositionDelegate(SetChildrenPosition), new Object()); } private void AnimateRadius(double start, double end) { DoubleAnimation ani = new DoubleAnimation(); ani.From = start; ani.To = end; ani.FillBehavior = FillBehavior.HoldEnd; ani.Duration = new Duration(new TimeSpan(0, 0, 0, 3, 0)); ani.Completed += delegate { Console.WriteLine("ani ended"); }; this.BeginAnimation(AppPart.radiusProperty, ani); } }

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  • Question about Multicast Delegates?

    - by IbrarMumtaz
    I am going through some exam questions for the 70-536 exam and an actual question one developer posted on his blog has popped up in my exam questions. I cannot remember what his answer was .... but below is the question: You need to write a multicast delegate that accepts a DateTime argument and returns a bool value. Which code segment should you use? A: public delegate int PowerDeviceOn(bool, DateTime) B: public delegate bool PowerDeviceOn(Object, EventArgs) C: public delegate void PowerDeviceOn(DateTime) D: public delegate bool PowerDeviceOn(DateTime) The answer is A. Can someone please explain why? As I already did some research into this question a while ago and so I was sure that it was C, obviously now looking back at the question its clear that I did not read properly. As i was sure I had seen the same one before so I jumped to the most obvious one. A variation on this question: You need to write a multicast delegate that accepts a DateTime argument. Which code segment should you use? A: public delegate int PowerDeviceOn(bool, DateTime) B: public delegate bool PowerDeviceOn(Object, EventArgs) C: public delegate void PowerDeviceOn(DateTime) D: public delegate bool PowerDeviceOn(DateTime) Now this is another variation on this question, it still has the same bogus sample answers, as they still kind work in throwing the exam taker off. Notice how by simply keeping the sample answers the same and by removing a small portion of the question text, the answer is C and not A. The variation has no official answer as I just conjured it up using the exam question as a baseplate. The answer is definitely C. This time round its easy to see why C is correct but the very first question I have an inkling but as you know an inkling is not good enough in passing exams. Thanks For Reading.

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  • Understanding AddHandler and pass delegates and events.

    - by Achilles
    I am using AddHandler to wire a function to a control's event that I dynamically create: Public Sub BuildControl(EventHandler as System.Delegate) dim objMyButton as new button AddHandler objMyButton.Click, EventHandler end Sub This code is generating a run-time exception stating: Unable to cast object of type 'MyEventHandlerDelegate' to type 'System.EventHandler' What am I not understanding about System.Delegate even though AddHandler takes as an argument of type "System.Delegate"? What Type does "EventHandler need to be to cast to a type that AddHandler can accept? Thanks for your help!

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  • Logging class using delegates (NullReferenceException)

    - by Leroy Jenkins
    I have created a small application but I would now like to incorporate some type of logging that can be viewed via listbox. The source of the data can be sent from any number of places. I have created a new logging class that will pass in a delegate. I think Im close to a solution but Im receiving a NullReferenceException and I don’t know the proper solution. Here is an example of what Im trying to do: Class1 where the inbound streaming data is received. class myClass { OtherClass otherClass = new OtherClass(); otherClass.SendSomeText(myString); } Logging Class class OtherClass { public delegate void TextToBox(string s); TextToBox textToBox; Public OtherClass() { } public OtherClass(TextToBox ttb) { textToBox = ttb; } public void SendSomeText(string foo) { textToBox(foo); } } The Form public partial class MainForm : Form { OtherClass otherClass; public MainForm() { InitializeComponent(); otherClass = new OtherClass(this.TextToBox); } public void TextToBox(string pString) { listBox1.Items.Add(pString); } } Whenever I receive data in myClass, its throwing an error. Any help you could give would be appreciated.

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  • When using delegates, need better way to do sequential processing

    - by Padawan
    I have a class WebServiceCaller that uses NSURLConnection to make asynchronous calls to a web service. The class provides a delegate property and when the web service call is done, it calls a method webServiceDoneWithXXX on the delegate. There are several web service methods that can be called, two of which are say GetSummary and GetList. The classes that use WebServiceCaller initially need both the summary and list so they are written like this: -(void)getAllData { [webServiceCaller getSummary]; } -(void)webServiceDoneWithGetSummary { [webServiceCaller getList]; } -(void)webServiceDoneWithGetList { ... } This works but there are at least two problems: The calls are split across delegate methods so it's hard to see the sequence at a glance but more important it's hard to control or modify the sequence. Sometimes I want to call just GetSummary and not also GetList so I would then have to use an ugly class-level state variable that tells webServiceDoneWithGetSummary whether to call GetList or not. Assume that GetList cannot be done until GetSummary completes and returns some data which is used as input to GetList. Is there a better way to handle this and still get asynchronous calls? Update based on Matt Long's answer: Using notifications instead of a delegate, it looks like I can solve problem #2 by setting a different selector depending on whether I want the full sequence (GetSummary+GetList) or just GetSummary. Both observers would still use the same notification name when calling GetSummary. I would have to write two separate methods to handle GetSummaryDone instead of using a single delegate method (where I would have needed some class-level variable to tell whether to then call GetList). -(void)getAllData { [[NSNotificationCenter defaultCenter] addObserver:self              selector:@selector(getSummaryDoneAndCallGetList:)                  name:kGetSummaryDidFinish object:nil];     [webServiceCaller getSummary]; } -(void)getSummaryDoneAndCallGetList { [NSNotificationCenter removeObserver] //process summary data [[NSNotificationCenter defaultCenter] addObserver:self              selector:@selector(getListDone:)                  name:kGetListDidFinish object:nil];     [webServiceCaller getList]; } -(void)getListDone { [NSNotificationCenter removeObserver] //process list data } -(void)getJustSummaryData { [[NSNotificationCenter defaultCenter] addObserver:self              selector:@selector(getJustSummaryDone:) //different selector but                  name:kGetSummaryDidFinish object:nil]; //same notification name     [webServiceCaller getSummary]; } -(void)getJustSummaryDone { [NSNotificationCenter removeObserver] //process summary data } I haven't actually tried this yet. It seems better than having state variables and if-then statements but you have to write more methods. I still don't see a solution for problem 1.

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  • Implement delegates for Core Data's fetched results controller or not

    - by Spanky
    What advantage is there to implementing the four delegate methods: (void)controllerWillChangeContent:(NSFetchedResultsController *)controller (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id )sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath (void)controllerDidChangeContent:(NSFetchedResultsController *)controller rather than implement: (void)controllerDidChangeContent:(NSFetchedResultsController *)controller Any help appreciated // :)

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  • Delegates And Cross Thread Exception

    - by Neo
    Whenever i am updating UI in windows form using delegate it gives me cross thread exception why it is happening like this? is there new thread started for each delegate call ? void Port_DataReceived(object sender, SerialDataReceivedEventArgs e) { //this call delegate to display data clsConnect(statusMsg); } protected void displayResponse(string resp) { //here cross thread exception occur if directly set to lblMsgResp.Text="Test"; if (lblMsgResp.InvokeRequired) { lblMsgResp.Invoke(new MethodInvoker(delegate { lblMsgResp.Text = resp; })); } }

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  • Question about Multicaste Delegates?

    - by IbrarMumtaz
    I am going through some exam questions for the 70-536 exam and an actual question one developer postedon his blog has popped up in my exam questions. I cannot remember what his answer was .... but below is the question: You need to write a multicast delegate that accepts a DateTime arguement and returns a bool value. Which code segment should you use? A: public delegate int PowerDeviceOn(bool, DateTime) B: public delegate bool PowerDeviceOn(Object, EventArgs) C: public delegate void PowerDeviceOn(DateTime) D: public delegate bool PowerDeviceOn(DateTime) The answer is A. Can someone please explain why? As I already did some research into this question a while ago and so I was sure that it was C, obviously now looking back at the question its clear that I did not read properly. As i was sure I had seen the same one before so I jumped to the most obvious one. A varitation on this question: You need to write a multicast delegate that accepts a DateTime arguement. Which code segment should you use? A: public delegate int PowerDeviceOn(bool, DateTime) B: public delegate bool PowerDeviceOn(Object, EventArgs) C: public delegate void PowerDeviceOn(DateTime) D: public delegate bool PowerDeviceOn(DateTime) Now this is another variation on this quesiton, it still has the same bogus sample answers, as they still kind work in throwing the exam taker off. Notice how by simply keeping the sample asnwers the same and by removing a small portion of the question text, the answer is C and not A. The variation has no official answer as I just conjured it up using the exam question as a baseplate. The answer is definately C. This time round its easy to see why C is correctr but the very first question I have an inkiling but as you know an inkling is not good enough in passing exams. Thanks For Reading.

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