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  • Instantiating a context in LINQ to Entities

    - by Jagd
    I've seen two different manners that programmers approach when creating an entity context in their code. The first is like such, and you can find it all over the MSDN code examples: public void DoSomething() { using TaxableEducationEntities context = new TaxableEducationEntities()) { // business logic and whatever else } } The second is to create the context as a private attribute in some class that encapsulates your business logic. So you would have something like: public class Education_LINQ { private TaxableEducationEntities context = new TaxableEducationEntities(); public void DoSomething() { var result = from a in context.luAction select a; // business logic and whatever else } } Which way is more efficient? Assume that you have two methods, one called DoSomething1() and another called DoSomething2(), and both methods incorporate the using statement to open the context and do whatever with it. Were you to call one method after the other, would there be any superfluous overhead going on, since essentially both methods create the context and then clean it up when they're done? As opposed to having just one private attribute that is created when a class object is instantiated, and then in turn cleaned up when the object goes out of scope?

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  • CheckBox ListView SelectedValues DependencyProperty Binding

    - by Ristogod
    I am writing a custom control that is a ListView that has a CheckBox on each item in the ListView to indicate that item is Selected. I was able to do so with the following XAML. <ListView x:Class="CheckedListViewSample.CheckBoxListView" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" mc:Ignorable="d"> <ListView.Style> <Style TargetType="{x:Type ListView}"> <Setter Property="SelectionMode" Value="Multiple" /> <Style.Resources> <Style TargetType="ListViewItem"> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="ListViewItem"> <Border BorderThickness="{TemplateBinding Border.BorderThickness}" Padding="{TemplateBinding Control.Padding}" BorderBrush="{TemplateBinding Border.BorderBrush}" Background="{TemplateBinding Panel.Background}" SnapsToDevicePixels="True"> <CheckBox IsChecked="{Binding IsSelected, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ListViewItem}}}"> <CheckBox.Content> <ContentPresenter Content="{TemplateBinding ContentControl.Content}" ContentTemplate="{TemplateBinding ContentControl.ContentTemplate}" HorizontalAlignment="{TemplateBinding Control.HorizontalContentAlignment}" VerticalAlignment="{TemplateBinding Control.VerticalContentAlignment}" SnapsToDevicePixels="{TemplateBinding UIElement.SnapsToDevicePixels}" /> </CheckBox.Content> </CheckBox> </Border> </ControlTemplate> </Setter.Value> </Setter> </Style> </Style.Resources> </Style> </ListView.Style> </ListView> I however am trying to attempt one more feature. The ListView has a SelectedItems DependencyProperty that returns a collection of the Items that are checked. However, I need to implement a SelectedValues DependencyProperty. I also am implementing a SelectedValuesPath DependencyProperty. By using the SelectedValuesPath, I indicate the path where the values are found for each selected item. So if my items have an ID property, I can specify using the SelectedValuesPath property "ID". The SelectedValues property would then return a collection of ID values. I have this working also using this code in the code-behind: using System.Windows; using System.Windows.Controls; using System.ComponentModel; using System.Collections; using System.Collections.Generic; namespace CheckedListViewSample { /// <summary> /// Interaction logic for CheckBoxListView.xaml /// </summary> public partial class CheckBoxListView : ListView { public static DependencyProperty SelectedValuesPathProperty = DependencyProperty.Register("SelectedValuesPath", typeof(string), typeof(CheckBoxListView), new PropertyMetadata(string.Empty, null)); public static DependencyProperty SelectedValuesProperty = DependencyProperty.Register("SelectedValues", typeof(IList), typeof(CheckBoxListView), new PropertyMetadata(new List<object>(), null)); [Category("Appearance")] [Localizability(LocalizationCategory.NeverLocalize)] [Bindable(true)] public string SelectedValuesPath { get { return ((string)(base.GetValue(CheckBoxListView.SelectedValuesPathProperty))); } set { base.SetValue(CheckBoxListView.SelectedValuesPathProperty, value); } } [Bindable(true)] [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)] [Category("Appearance")] public IList SelectedValues { get { return ((IList)(base.GetValue(CheckBoxListView.SelectedValuesPathProperty))); } set { base.SetValue(CheckBoxListView.SelectedValuesPathProperty, value); } } public CheckBoxListView() : base() { InitializeComponent(); base.SelectionChanged += new SelectionChangedEventHandler(CheckBoxListView_SelectionChanged); } private void CheckBoxListView_SelectionChanged(object sender, SelectionChangedEventArgs e) { List<object> values = new List<object>(); foreach (var item in SelectedItems) { if (string.IsNullOrWhiteSpace(SelectedValuesPath)) { values.Add(item); } else { try { values.Add(item.GetType().GetProperty(SelectedValuesPath).GetValue(item, null)); } catch { } } } base.SetValue(CheckBoxListView.SelectedValuesProperty, values); e.Handled = true; } } } My problem is that my binding only works one way right now. I'm having trouble trying to figure out how to implement my SelectedValues DependencyProperty so that I could Bind a Collection of values to it, and when the control is loaded, the CheckBoxes are checked with items that have values that correspond to the SelectedValues. I've considered using the PropertyChangedCallBack event, but can't quite figure out how I could write that to achieve my goal. I'm also unsure of how I find the correct ListViewItem to set it as Selected. And lastly, if I can find the ListViewItem and set it to be Selected, won't that fire my SelectionChanged event each time I set a ListViewItem to be Selected?

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  • C# generic list <T> how to get the type of T?

    - by Daok
    Hello, Let say I have a List< T > abc = new List< T >; inside a class public class MyClass<T>//.... Later, when I initialize the class the T because MyTypeObject1. So I have a generic list of List< MyTypeObject1 >. I would like to know, what type of object the list of my class contain. Example, the list called abc contain what type of object? I cannot do abc[0].GetType(); because the list might contain 0 element. How can I do it?

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  • Eager loading vs. many queries with PHP, SQLite

    - by Mike
    I have an application that has an n+1 query problem, but when I implemented a way to load the data eagerly, I found absolutely no performance gain. I do use an identity map, so objects are only created once. Here's a benchmark of ~3000 objects. first query + first object creation: 0.00636100769043 sec. memory usage: 190008 bytes iterate through all objects (queries + objects creation): 1.98003697395 sec. memory usage: 7717116 bytes And here's one when I use eager loading. query: 0.0881109237671 sec. memory usage: 6948004 bytes object creation: 1.91053009033 sec. memory usage: 12650368 bytes iterate through all objects: 1.96605396271 sec. memory usage: 12686836 bytes So my questions are Is SQLite just magically lightning fast when it comes to small queries? (I'm used to working with MySQL.) Does this just seem wrong to anyone? Shouldn't eager loading have given much better performance?

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  • Android::Webview removes scrollbar for a DIV

    - by Legend
    I made a small webpage with a scrollable div. When I load it in a browser, it works fine. But when I load it in a webview inside Android, it doesn't let me scroll the div. Is there a workaround for this or do I have to use a different design? I am talking about websites like this.

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  • Asynchronous Sockets - Handling false socket.AcceptAsync values

    - by David
    The Socket class has a method .AcceptAsync which either returns true or false. I'd thought the false return value was an error condition, but in the samples Microsoft provide for Async sockets they call the callback function synchronously after checking for failure, as shown here: public void StartAccept(SocketAsyncEventArgs acceptEventArg) { if (acceptEventArg == null) { acceptEventArg = new SocketAsyncEventArgs(); acceptEventArg.Completed += new EventHandler<SocketAsyncEventArgs>(AcceptEventArg_Completed); } else { // socket must be cleared since the context object is being reused acceptEventArg.AcceptSocket = null; } m_maxNumberAcceptedClients.WaitOne(); bool willRaiseEvent = listenSocket.AcceptAsync(acceptEventArg); if (!willRaiseEvent) { ProcessAccept(acceptEventArg); } } /// <summary> /// This method is the callback method associated with Socket.AcceptAsync operations and is invoked /// when an accept operation is complete /// </summary> void AcceptEventArg_Completed(object sender, SocketAsyncEventArgs e) { ProcessAccept(e); } Why do they do this? It defeats the purpose of asynchronous sockets and stops the method from returning.

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  • Winforms Hotkey, Help?

    - by Di4g0n4leye
    namespace WebBrowser { public partial class MainForm : Form { public MainForm() { InitializeComponent(); } int GetPixel(int x, int y) { Bitmap bmp = new Bitmap(1, 1, PixelFormat.Format32bppPArgb); Graphics grp = Graphics.FromImage(bmp); grp.CopyFromScreen(new Point(x,y), Point.Empty, new Size(1,1)); grp.Save(); return bmp.GetPixel(0, 0).ToArgb(); } void Button1Click(object sender, EventArgs e) { int x = Cursor.Position.X; int y = Cursor.Position.Y; int pixel = GetPixel(x,y); textBox1.Text = pixel.ToString(); } void MainFormLoad(object sender, EventArgs e) { webBrowser1.Navigate("http://google.com"); } } } } i want to add a hotkey that call Button1 on Press, How can that be done?

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  • SQLDependency thread

    - by user171523
    i am in the process implementing SQLdepenency i would like to know in case of Dependency Handler exeuctues will it spun a different thred from main Process ? What will happen when the event handler triggers? Do i need to worry about any multithreds issues? public void CreateSqlDependency() { try { using (SqlConnection connection = (SqlConnection)DBFactory.GetDBFactoryConnection(Constants.SQL_PROVIDER_NAME)) { SqlCommand command = (SqlCommand)DBFactory.GetCommand(Constants.SQL_PROVIDER_NAME); command.CommandText = watchQuery; command.CommandType = CommandType.Text; SqlDependency dependency = new SqlDependency(command); //Create the callback object dependency.OnChange += new OnChangeEventHandler(this.QueueChangeNotificationHandler); SqlDependency.Start(connectionString); DataTable dataTable = DBFactory.ExecuteSPReDT(command); } } catch (SqlException sqlExp) { throw sqlExp; } catch (Exception ex) { throw ex; } } public void QueueChangeNotificationHandler(object caller, SqlNotificationEventArgs e) { if(e.Info == SqlNotificationInfo.Insert) Fire(); }

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  • Alternative of JPA

    - by Peter
    I want to use JPA for my persistence layer of my Java Desktop Application but I have the similar problem as describe at http://stackoverflow.com/questions/2562746/jpa-entity-design-problem/2563009#2563009 I didn't find a solution to the above kind of problem that's why I want to go with any other alternative of JPA. It would be better if I get the solution of the above problem.

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  • Client Side Includes on HTML pages

    - by Roy Rico
    Previously I had thought that there were only ways to get content from external URLs into your page. These 2 ways are use an IFRAME or Javascript to include it into your pages. I've just learned of a new way using the tag. <object type="text/html" frameborder="0" data="http://Server/URL/"></object> I have found some content online that confirms this ability, but it doesn't talk much about features such as Accessibility and SEO of the page. Does anyone have any experience with this? Is there any information available regarding using this method and how it effects Accessibility and SEO?

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  • Get input from user with ActivityBuilder in WF 4

    - by avi1234
    Hi, I am trying to write a simple activity that received from the user its name and printing "hello + username" message. the problem is that i cannot access to the username input via code. the function is: static ActivityBuilder CreateTask1() { Dictionary<string, object> properties = new Dictionary<string, object>(); properties.Add("User_Name", new InArgument<string>()); var res = new ActivityBuilder(); res.Name = "Task1"; foreach (var item in properties) { res.Properties.Add(new DynamicActivityProperty { Name = item.Key, Type = item.Value.GetType(), Value = item.Value }); } Sequence c = new Sequence(); c.Activities.Add(new WriteLine { Text = "Hello " + properties["User_Name"] }); res.Implementation = c; return res; } The output of the followed will always be "Hello User_Name". Thanks!

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  • How to hide GetType() method from COM?

    - by ticky
    I made an automation Add-In for Excel, and I made several functions (formulas). I have a class which header looks like this (it is COM visible): [ClassInterface(ClassInterfaceType.AutoDual)] [ComVisible(true)] public class Functions {} In a list of methods, I see: ToString(), Equals(), GetHashCode() and GetType() methods. Since all methods of my class are COM visible, I should somehow hide those 4. I succeeded with 3 of them: ToString(), Equals(), GetHashCode() but GetType() cannot be overriden. Here is what I did with 3 of them: [ComVisible(false)] public override string ToString() { return base.ToString(); } [ComVisible(false)] public override bool Equals(object obj) { return base.Equals(obj); } [ComVisible(false)] public override int GetHashCode() { return base.GetHashCode(); } This doesn't work: [ComVisible(false)] public override Type GetType() { return base.GetType(); } Here is the error message in Visual Studio when compile: ..GetType()': cannot override inherited member 'object.GetType()' because it is not marked virtual, abstract, or override So, what should I do to hide the GetType() method from COM?

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  • EJB3 lookup on websphere

    - by dcp
    I'm just starting to try to learn Websphere, and I have my ejb deployed, but I cannot look it up. Here's is what I have: public class RemoteEJBCount { public static Context ctx; private static String jndiNameStateless = "EJB3CounterSample/EJB3Beans.jar/StatelessCounterBean/com/ibm/websphere/ejb3sample/counter/RemoteCounter"; public static void main(String[] args) throws NamingException { RemoteCounter statelessCounter; Hashtable<String, Object> env = new Hashtable<String, Object>(); env.put(Context.PROVIDER_URL, "corbaloc:iiop:localhost:2809"); env.put(Context.INITIAL_CONTEXT_FACTORY, "com.ibm.websphere.naming.WsnInitialContextFactory"); ctx = new InitialContext(env); statelessCounter = (RemoteCounter)ctx.lookup(jndiNameStateless); } } Is there something I need to be doing differently to look up the EJB?

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  • Unable to understand "A field initializer cannot reference the nonstatic field" Error?

    - by Subhen
    Hi, I am getting the error "A field initializer cannot reference the nonstatic field", While My code is as below: Object selectedItem = PageVariables.slectedItemData; MyClass selectedItems = (MyClass)selectedItem; But the same thing works if assign the value at the constructor or in a different method , like below: public partial class MusicPlayer : Page { Object selectedItem = PageVariables.slectedItemData; public MusicPlayer() { InitializeComponent(); MyClass selectedItems = (MyClass)selectedItem; } } I am just trying to understand what is the difference, Why it is looking for a static varaible declaration(in 1st case) while doesn't look for it while in a constructor or a different method!!!

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  • A leader election algorithm for an oriented hypercube

    - by mick
    I'm stuck with some problem where I have to design a leader election algorithm for an oriented hypercube. This should be done by using a tournament with a number of rounds equal to the dimension D of the hypercube. In each stage d, with 1 <= d < D two candidate leaders of neighbouring d-dimensional hypercubes should compete to become the single candidate leader of the (d+1)-dimensional hypercube that is the union of their respective hypercubes.

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  • Why does DataSet.HasChanges() return true if called in the same function as change but false otherwi

    - by Chapso
    Assuming that the buttons are being clicked in order, the following code modifies row 1 in a .net DataSet, then row 0. HasChanges returns true, but GetChanges only gives me the change for row 0. If I comment out the line in the button2 click event that modifies row 0, then HasChanges returns false. Can anyone explain to me why HasChanges() and GetChanges() only return true when they are called in the same function as the change to the DataSet? Protected Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click __ds1.Tables(0).Rows(1)("EmployeeName") = "TestStuff" End Sub Protected Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click __ds1.Tables(0).Rows(0)("EmployeeName") = "TestStuff" If __ds1.HasChanges(DataRowState.Modified Or DataRowState.Added) Then __ds2 = __ds1.GetChanges(DataRowState.Modified _ Or DataRowState.Added) GridView3.DataSource = __ds2.Tables("Users").DefaultView GridView3.DataBind() Else End If End Sub

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  • Is it a bad practice to pass "this" as an argument?

    - by Anna Lear
    I'm currently tempted to write the following: public class Class1() { public Class1() { MyProperty = new Class2(this); } public Class2 MyProperty { get; private set; } } public class Class2() { public Class2(Class1 class1) { ParentClass1 = class1; } public Class1 ParentClass1 { get; set; } } Is passing "this" as an argument a sign of a design problem? What would be a better approach?

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  • Strange error inserting new relationship data in core-data

    - by michael
    My app will allow users to create a personalised list of events from a large list of events. I have a table view which simply displays these events, tapping on one of them takes the user to the event details view, which has a button "add to my events". In this detailed view I own the original event object, retrieved via an NSFetchedResultsController and passed to the detailed view (via a table cell, the same as the core data recipes sample). I have no trouble retrieving/displaying information from this "event". I am then trying to add it to the list of MyEvents represented by a one to many (inverse) relationship: This code: NSManagedObjectContext *context = [event managedObjectContext]; MyEvents *myEvents = (MyEvents *)[NSEntityDescription insertNewObjectForEntityForName:@"MyEvents" inManagedObjectContext:context]; [myEvents addEventObject:event];//ERROR And this code (suggested below): //would this add to or overwrite the "list" i am attempting to maintain NSManagedObjectContext *context = [event managedObjectContext]; MyEvents *myEvents = (MyEvents *)[NSEntityDescription insertNewObjectForEntityForName:@"MyEvents" inManagedObjectContext:context]; NSMutableSet *myEvent = [myEvents mutableSetValueForKey:@"event"]; [myEvent addObject:event]; //ERROR Bot produce (at the line indicated by //ERROR): *** -[NSComparisonPredicate evaluateWithObject:]: message sent to deallocated instance Seems I may have missed something fundamental. I cant glean any more information through the use of debugging tools, with my knowledge of them. 1) Is this a valid way to compile and store an editable list like this? 2) Is there a better way? 3) What could possibly be the deallocated instance in error? -- I have now modified the Event entity to have a to-many relationship called "myEvents" which referrers to itself. I can add Events to this fine, and logging the object shows the correct memory addresses appearing for the relationship after a [event addMyEventObject:event];. The same failure happens right after this however. I am still at a loss to understand what is going wrong. This is the backtrace #0 0x01f753a7 in ___forwarding___ () #1 0x01f516c2 in __forwarding_prep_0___ () #2 0x01c5aa8f in -[NSFetchedResultsController(PrivateMethods) _preprocessUpdatedObjects:insertsInfo:deletesInfo:updatesInfo:sectionsWithDeletes:newSectionNames:treatAsRefreshes:] () #3 0x01c5d63b in -[NSFetchedResultsController(PrivateMethods) _managedObjectContextDidChange:] () #4 0x0002e63a in _nsnote_callback () #5 0x01f40005 in _CFXNotificationPostNotification () #6 0x0002bef0 in -[NSNotificationCenter postNotificationName:object:userInfo:] () #7 0x01bbe17d in -[NSManagedObjectContext(_NSInternalNotificationHandling) _postObjectsDidChangeNotificationWithUserInfo:] () #8 0x01c1d763 in -[NSManagedObjectContext(_NSInternalChangeProcessing) _createAndPostChangeNotification:withDeletions:withUpdates:withRefreshes:] () #9 0x01ba25ea in -[NSManagedObjectContext(_NSInternalChangeProcessing) _processRecentChanges:] () #10 0x01bdfb3a in -[NSManagedObjectContext processPendingChanges] () #11 0x01bd0957 in _performRunLoopAction () #12 0x01f4d252 in __CFRunLoopDoObservers () #13 0x01f4c65f in CFRunLoopRunSpecific () #14 0x01f4bc48 in CFRunLoopRunInMode () #15 0x0273878d in GSEventRunModal () #16 0x02738852 in GSEventRun () #17 0x002ba003 in UIApplicationMain () Cheers.

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  • How to add a view helper directory (zend framework)

    - by Cédric Girard
    Hi, I begin with ZF (1.9.7), and I want to use View Helpers from a library shared between all my projects. But I can't find how to add it directory to the helpers path. My herpers works fines when I put them in application's helpers path. Here is the error, where I find the path to ZF helpers, and path to the applications ones. object(ArrayObject)#71 (3) { ["exception"]=> object(Zend_Loader_PluginLoader_Exception)#70 (6) { ["message:protected"]=> string(151) "Plugin by name 'Voo' was not found in the registry; used paths: Zend_View_Helper_: Zend/View/Helper/;C:/ZendStd/www/applis/VOO4_PROJECTX/views\helpers/" ["string:private"]=> string(0) "" ["code:protected"]=> int(0) ["file:protected"]=> string(89) "C:\Program Files\Zend\ZendServer\share\ZendFramework\library\Zend\Loader\PluginLoader.php" ["line:protected"]=> int(401) Best regards Cédric

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  • Which is the best alternative for Java Serialization?

    - by Alotor
    I'm currently working on a project which needs to persist any kind of objects (of which implementation we don't have any control) so these objects could be recovered afterwards. We can't implement a ORM because we can't restrict the users of our library at development time. Our first alternative was to serialize it with the Java default serialization but we had a lot of trouble recovering the objects when the users started to pass different versions of the same object (attributes changed types, names, ...). We have tried with the XMLEncoder class (transforms an object into a XML), but we have found that there is a lack of functionality (doesn't support Enums for example). Finally, we also tried JAXB but this impose our users to annotate their classes. Any good alternative?

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  • Use ASP.Net server control code generation from .ashx

    - by Matt Dawdy
    I'm trying to take an existing bunch of code that was previously on a full .aspx page, and do the same stuff in a .ashx handler. The code created an HtmlTable object, added rows and cells to those rows, then added that html table the .aspx's controls collection, then added it to a div that was already on the page. I am trying to keep the code in tact but instead of putting the control into a div, actually generate the html and I'll return that in a big chunk of text that can be called via AJAX client-side. HtmlTable errors out when I try to use the InnerHtml property (says it isn't supported), and when I try RenderControl, after making first a TextWriter and next an HtmlTextWriter object, I get the error that Page cannot be null. Has anyone done this before? Any suggestions?

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  • What is a NullReferenceException in .NET?

    - by John Saunders
    (I'm creating this separate question and answer because every question we get on NullReferenceException is really the same) I have some code and when it executes, it throws a NullReferenceException, saying, "Object reference not set to an instance of an object.". What does this mean, and what can I do about it? Note again, that this is a question meant to focus answers to the canonical "what is a NullReferenceException and why did I get one" question. I do know what a NullReferenceException is, as my answer below demonstrates.

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  • Core Data - NSPredicate to filter to-many relationship

    - by Macatomy
    I have 2 entities, Task and List. Each task has a to-one relationship to a List object called "list", and there is an inverse relationship with List, which has a to-many relationship with Task called "tasks". I'm trying to use a fetch request with an NSPredicate to get all the Task objects that belong to a specified List: NSPredicate *predicate = [NSPredicate predicateWithFormat:@"list=%@", theList]; [fetchRequest setPredicate:predicate]; (where "theParent" is a reference to a List object). However this returns no fetched objects. If I take out the predicate, then the objects are returned (so I do know they exist, and by NSLogging theList I know it has Task objects associated with it). Thanks

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