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• Instance caching in Objective C

  - by zoul

  Hello! I want to cache the instances of a certain class. The class keeps a dictionary of all its instances and when somebody requests a new instance, the class tries to satisfy the request from the cache first. There is a small problem with memory management though: The dictionary cache retains the inserted objects, so that they never get deallocated. I do want them to get deallocated, so that I had to overload the release method and when the retain count drops to one, I can remove the instance from cache and let it get deallocated. This works, but I am not comfortable mucking around the release method and find the solution overly complicated. I thought I could use some hashing class that does not retain the objects it stores. Is there such? The idea is that when the last user of a certain instance releases it, the instance would automatically disappear from the cache. NSHashTable seems to be what I am looking for, but the documentation talks about “supporting weak relationships in a garbage-collected environment.” Does it also work without garbage collection? Clarification: I cannot afford to keep the instances in memory unless somebody really needs them, that is why I want to purge the instance from the cache when the last “real” user releases it. Better solution: This was on the iPhone, I wanted to cache some textures and on the other hand I wanted to free them from memory as soon as the last real holder released them. The easier way to code this is through another class (let’s call it TextureManager). This class manages the texture instances and caches them, so that subsequent calls for texture with the same name are served from the cache. There is no need to purge the cache immediately as the last user releases the texture. We can simply keep the texture cached in memory and when the device gets short on memory, we receive the low memory warning and can purge the cache. This is a better solution, because the caching stuff does not pollute the Texture class, we do not have to mess with release and there is even a higher chance for cache hits. The TextureManager can be abstracted into a ResourceManager, so that it can cache other data, not only textures.

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• Zend Framework - Can view helpers be user inside of partials?

  - by Bob Spryn

  Working on implementing view helpers and partials to create a group of reusable display objects. Previously addressed in my question here: http://stackoverflow.com/questions/2389531/zend-framework-when-to-use-viewscripts-partials-vs-view-helpers Wondering if partials can call view helpers of their own, and if they can whether those helpers will have access to the original view (since the partials don't).

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• Attempted to render a circle in opengl es 1.1, renders as oval

  - by eipxen

  Hi all, I attempted to render a circle in opengl es 1.1 as a test before building a larger program, but it renders as an oval. Here is the code I use to generate and render my vertices: static const int numVerts = 40; static GLfloat myFirstCircle[82]; myFirstCircle[0] = 0.0f; myFirstCircle[1] = 0.0f; for (int i = 2; i < (numVerts+1)*2; i+=2) { myFirstCircle[i] = .5 * cosf(i*2*3.14159/numVerts); myFirstCircle[i+1] = .5 * sinf(i*2*3.14159/numVerts); } glVertexPointer(2, GL_FLOAT, 0, myFirstCircle); glEnableClientState(GL_VERTEX_ARRAY); glDrawArrays(GL_TRIANGLE_FAN, 0, 22); I'm still somewhat new to this system, so I may have a silly error that I do not see, but it seems to me like this should generate 40 vertices on a circle of radius .5. When it renders, the shape on screen appears to be an oval, significantly taller than it is wide. My question is thus: why is my circle rendering this way, and what could I do to fix it? This is the first question on stackoverflow, so I'm not sure how to share an image of my output.

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• Changing the path a property is bound to at runtime

  - by Dave Colwell

  Hi, I have a ComboBox with a list of objects bound to it. Currently i have the items templated so they show only the property Class.Name. so the ComboBox is full of Class.Name However i am required to give the user the option to display the property Class.Description instead. If it were just that easy i would be fine, but they want the option to switch back and forth between them at runtime. Any ideas?

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• How can I pass in a params of Expression<Func<T, object>> to a method?

  - by Pure.Krome

  Hi folks, I have the following two methods :- public static IQueryable<T> IncludeAssociations<T>(this IQueryable<T> source, params string[] associations) { ... } public static IQueryable<T> IncludeAssociations<T>(this IQueryable<T> source, params Expression<Func<T, object>>[] expressions) { ... } Now, when I try and pass in a params of Expression<Func<T, object>>[], it always calls the first method (the string[]' and of course, that value isNULL`) Eg. Expression<Func<Order, object>> x1 = x => x.User; Expression<Func<Order, object>> x2 = x => x.User.Passport; var foo = _orderRepo .Find() .IncludeAssociations(new {x1, x2} ) .ToList(); Can anyone see what I've done wrong? Why is it thinking my params are a string? Can I force the type, of the 2x variables?

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• Can't decrypt after encrypting with blowfish Java

  - by user2030599

  Hello i'm new to Java and i have the following problem: i'm trying to encrypt the password of a user using the blowfish algorithm, but when i try to decrypt it back to check the authentication it fails to decrypt it for some reason. public static String encryptBlowFish(String to_encrypt, String salt){ String dbpassword = null; try{ SecretKeySpec skeySpec = new SecretKeySpec( salt.getBytes(), "Blowfish" ); // Instantiate the cipher. Cipher cipher = Cipher.getInstance("Blowfish/CBC/PKCS5Padding"); cipher.init(Cipher.ENCRYPT_MODE, skeySpec); //byte[] encrypted = cipher.doFinal( URLEncoder.encode(data).getBytes() ); byte[] encrypted = cipher.doFinal( to_encrypt.getBytes() ); dbpassword = new String(encrypted); } catch (Exception e) { System.out.println("Exception while encrypting"); e.printStackTrace(); dbpassword = null; } finally { return dbpassword; } } public static String decryptBlowFish(String to_decrypt, String salt){ String dbpassword = null; try{ SecretKeySpec skeySpec = new SecretKeySpec( salt.getBytes(), "Blowfish" ); // Instantiate the cipher. Cipher cipher = Cipher.getInstance("Blowfish/CBC/PKCS5Padding"); cipher.init(Cipher.DECRYPT_MODE, skeySpec); //byte[] encrypted = cipher.doFinal( URLEncoder.encode(data).getBytes() ); byte[] encrypted = cipher.doFinal( to_decrypt.getBytes() ); dbpassword = new String(encrypted); } catch (Exception e) { System.out.println("Exception while decrypting"); e.printStackTrace(); dbpassword = null; } finally { return dbpassword; } } When i call the decrypt function it gives me the following error: java.security.InvalidKeyException: Parameters missing Any ideas? Thank you

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• Why Enumerable.Range is faster than a direct yield loop?

  - by Morgan Cheng

  Below code is checking performance of three different ways to do same solution. public static void Main(string[] args) { // for loop { Stopwatch sw = Stopwatch.StartNew(); int accumulator = 0; for (int i = 1; i <= 100000000; ++i) { accumulator += i; } sw.Stop(); Console.WriteLine("time = {0}; result = {1}", sw.ElapsedMilliseconds, accumulator); } //Enumerable.Range { Stopwatch sw = Stopwatch.StartNew(); var ret = Enumerable.Range(1, 100000000).Aggregate(0, (accumulator, n) => accumulator + n); sw.Stop(); Console.WriteLine("time = {0}; result = {1}", sw.ElapsedMilliseconds, ret); } //self-made IEnumerable<int> { Stopwatch sw = Stopwatch.StartNew(); var ret = GetIntRange(1, 100000000).Aggregate(0, (accumulator, n) => accumulator + n); sw.Stop(); Console.WriteLine("time = {0}; result = {1}", sw.ElapsedMilliseconds, ret); } } private static IEnumerable<int> GetIntRange(int start, int count) { int end = start + count; for (int i = start; i < end; ++i) { yield return i; } } } The result is like this: time = 306; result = 987459712 time = 1301; result = 987459712 time = 2860; result = 987459712 It is not surprising that "for loop" is faster than the other two solutions, because Enumerable.Aggregate takes more method invocations. However, it really surprises that "Enumerable.Range" is faster than the "self-made IEnumerable". I thought that Enumerable.Range will take more overhead than the simple GetIntRange method. What is the possible reason for this?

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• Why is this linq extension method hit the database twice?

  - by Pure.Krome

  Hi folks, I have an extension method called ToListIfNotNullOrEmpty(), which is hitting the DB twice, instead of once. The first time it returns one result, the second time it returns all the correct results. I'm pretty sure the first time it hits the database, is when the .Any() method is getting called. here's the code. public static IList<T> ToListIfNotNullOrEmpty<T>(this IEnumerable<T> value) { if (value.IsNullOrEmpty()) { return null; } if (value is IList<T>) { return (value as IList<T>); } return new List<T>(value); } public static bool IsNullOrEmpty<T>(this IEnumerable<T> value) { if (value != null) { return !value.Any(); } return true; } I'm hoping to refactor it so that, before the .Any() method is called, it actually enumerates through the entire list. If i do the following, only one DB call is made, because the list is already enumerated. var pewPew = (from x in whatever select x) .ToList() // This enumerates. .ToListIsNotNullOrEmpty(); // This checks the enumerated result. I sorta don't really want to call ToList() then my extension method. Any ideas, folks?

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• Applying the Decorator Pattern to Forms

  - by devoured elysium

  I am trying to apply the Decorator Design Pattern to the following situation: I have 3 different kind of forms: Green, Yellow, Red. Now, each of those forms can have different set of attributes. They can have a minimize box disabled, a maximized box disabled and they can be always on top. I tried to model this the following way: Form <---------------------------------------FormDecorator /\ /\ |---------|-----------| |----------------------|-----------------| GreenForm YellowForm RedForm MinimizeButtonDisabled MaximizedButtonDisabled AlwaysOnTop Here is my GreenForm code: public class GreenForm : Form { public GreenForm() { this.BackColor = Color.GreenYellow; } public override sealed Color BackColor { get { return base.BackColor; } set { base.BackColor = value; } } } FormDecorator: public abstract class FormDecorator : Form { private Form _decoratorForm; protected FormDecorator(Form decoratorForm) { this._decoratorForm = decoratorForm; } } and finally NoMaximizeDecorator: public class NoMaximizeDecorator : FormDecorator { public NoMaximizeDecorator(Form decoratorForm) : base(decoratorForm) { this.MaximizeBox = false; } } So here is the running code: static void Main() { Application.EnableVisualStyles(); Application.SetCompatibleTextRenderingDefault(false); Application.Run(CreateForm()); } static Form CreateForm() { Form form = new GreenForm(); form = new NoMaximizeDecorator(form); form = new NoMinimizeDecorator(form); return form; } The problem is that I get a form that isn't green and that still allows me to maximize it. It is only taking in consideration the NoMinimizeDecorator form. I do comprehend why this happens but I'm having trouble understanding how to make this work with this Pattern. I know probably there are better ways of achieving what I want. I made this example as an attempt to apply the Decorator Pattern to something. Maybe this wasn't the best pattern I could have used(if one, at all) to this kind of scenario. Is there any other pattern more suitable than the Decorator to accomplish this? Am I doing something wrong when trying to implement the Decorator Pattern? Thanks

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• Rhino Mocks - Do we really need stubs?

  - by Marcelo Oliveira

  If it's possible to change mock behaviour in Rhino Mocks using mock.Stub().Return(), why do we need Stubs anyway? What do we lose by always using MockRepository.GenerateMock()? One big benefit of using Mocks instead of Stubs is that we will be able to reuse the same instance among all the tests keeping them cleaner and straightforward. The moq framework works in a similar way... we don't have different objects for mocks and stubs. (please, don't answer with a link to Fowler's "Mocks aren't stubs" article)

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• how do I call a function from TOAD for Oracle and bind the result to a data grid

  - by neesh

  I have a function that takes as one of it's arguments a VARRAY of pl/sql Objects. How do I execute this stored procedure and bind the resultset that it returns to a data grid in TOAD for Oracle?

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• How do I add mouseClicked event to a swing table?

  - by Ayelet

  Hi, I am a new, terribly green user of Swing. I managed to create a table class using examples from java.sun tutorials, and I managed to load data dynamically into it. I want to be able to react to a click on a row by displaying a dialog box. How do I add the event Handler that will identify the selected row number? The main function code: public static void main(String[] args) { javax.swing.SwingUtilities.invokeLater(new Runnable() { public void run() { try { MainWindow window = new MainWindow(); window.frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Create and set up the content pane. createAndShowGUI(); //... and: private static void createAndShowGUI() { //Create and set up the window. JFrame frame = new JFrame("Data Table"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Create and set up data of the content pane. TableClass mainTable = new TableClass(fh.getColNames(), fh.getTableContent()); mainTable.setOpaque(true); frame.setContentPane(mainTable); //Display the window. frame.pack(); frame.setVisible(true); } Thank you

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• Why might my Xcode be crashing (or at least displaying an error on launch)?

  - by dsobol

  I am getting an error thrown when I launch my Xcode 3.2 all of a sudden: Uncaught Exception: * -[NSCFArray initWithObjects:count:]: attempt to insert nil object at objects[0] I can click through the error and Xcode seems to launch properly. I removed and reinstalled Xcode to no avail, and yet cannot find a config or perference that might be the culprit. I am running on 10.6.3 fwiw.... Has anyone else run into this problkem? TIA! Regards, Steve O'Sullivan

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• How can I get the type I want?

  - by Danny Chen

  There are a lot of such classes in my project (very old and stable code, I can't do many changes to them, maybe slight changes are OK) public class MyEntity { public long ID { get; set; } public string Name { get; set; } public decimal Salary { get; set; } public static GetMyEntity ( long ID ) { MyEntity e = new MyEntity(); // load data from DB and bind to this instance return e; } } For some reasons, now I need to do this: Type t = Type.GetType("XXX"); // XXX is one of the above classes' name MethodInfo staticM= t.GetMethods(BindingFlags.Public | BindingFlags.Static).FirstOrDefault();// I'm sure I can get the correct one var o = staticM.Invoke(...); //returns a object, but I want the type above! If I pass "MyEntity" at beginning, I hope I can get o as MyEntity! Please NOTE that I know the "name of the class" only. MyEntity e = staticM.Invoke(...) as MyEntity; can't be used here.

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• Avoiding 'Buffer Overrun' C6386 warning

  - by bdhar

  In my code, I am using an array xyz of 10 objects. When I am trying to access an element of the array using an unsigned int index like this: xyz[level], I get 'Buffer overrun' warning. Logically, I am pretty sure that level won't exceed 10. How to avoid this warning?

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• Flex: How do you list private attributes of a class?

  - by mensonge

  Hi, I try to serialize objects with their private attributes, in Flex. The introspection API does not seem to allow it: "The describeType() method returns only public members. The method does not return private members of the caller's superclass or any other class where the caller is not an instance." Is there another way for an instance to know the name of its private members?

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• How deserealizing JSON with GSON

  - by loko

  I have one result of APPI http://developer.yahoo.com/geo/placefinder/guide/examples.html, I need to deserealizing the result JSON of example only with GSON http://where.yahooapis.com/geocode?location=San+Francisco,+CA&flags=J&appid=yourappid But i dont now have to do the class for deserealizing one JSON with array This is the reponse: {"ResultSet": {"version":"1.0", "Error":0, "ErrorMessage":"No error", "Locale":"en_US", "Quality":40, "Found":1, "Results":[ {"quality":40, "latitude":"37.779160", "longitude":"-122.420049", "offsetlat":"37.779160", "offsetlon":"-122.420049", "radius":5000, "name":"", "line1":"", "line2":"San Francisco, CA", "line3":"", "line4":"United States", "house":"", "street":"", "xstreet":"", "unittype":"", "unit":"", "postal":"", "neighborhood":"", "city":"San Francisco", "county":"San Francisco County", "state":"California", "country":"United States", "countrycode":"US", "statecode":"CA", "countycode":"", "uzip":"94102", "hash":"C1D313AD706E3B3C", "woeid":12587707, "woetype":9}] } } Im trying to deserealizing of this way but i couldn´t do that, please help me to do the correct class to get the JSON with GSON. public class LocationAddress { private ResultSet resultset; public static class ResultSet{ private String version; private String Error; private String ErrorMessage; private List<Results> results; } public static class Results{ private String quality; private String latitude; private String longitude; public String getQuality() { return quality; } public void setQuality(String quality) { this.quality = quality; } public String getLatitude() { return latitude; } public void setLatitude(String latitude) { this.latitude = latitude; } public String getLongitude() { return longitude; } public void setLongitude(String longitude) { this.longitude = longitude; } } }

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• Dynamic casting using a generic interface

  - by Phil Whittaker

  Hi Is there any way to cast to a dynamic generic interface.. Site s = new Site(); IRepository<Site> obj = (IRepository<s.GetType()>)ServiceLocator.Current.GetInstance(t) obviously the above won't compile with this cast. Is there anyway to do a dynamic cast of a generic interface. I have tried adding a non generic interface but the system is looses objects in the Loc container. Thanks Phil

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• Mocking tools for c# on .NET

  - by Prasanth

  Im new to C#/.NET . But Ive been doing TDD for quite some time now. I wanted to what is the best framework that can be used for mocking objects while writing tests in c3

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• postgresql drop table

  - by Russell

  I have two tables (tbl and tbl_new) that both use the same sequence (tbl_id_seq). I'd like to drop one of those tables. On tbl, I've removed the modifier "not null default nextval('tbl_id_seq'::regclass)" but that modifier remains on tbl_new. I'm getting the following error: ERROR: cannot drop table tbl because other objects depend on it DETAIL: default for table tbl_new column id depends on sequence tbl_id_seq After reviewing http://www.postgresql.org/docs/9.1/static/sql-droptable.html It looks like there is only CASCADE and RESTRICT as options.

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• How can I test helpers blocks in Sinatra, using Rspec ?

  - by julien

  I'm writing a sinatra app and testing it with rspec and rack/test (as described on sinatrarb.com). It's been great so far, until I moved some rather procedural code from my domain objects to sinatra helpers. Since then, I've been trying to figure out how to test these in isolation ?

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• Multi-tier applications using L2S, WCF and Base Class

  - by Gena Verdel

  Hi all. One day I decided to build this nice multi-tier application using L2S and WCF. The simplified model is : DataBase-L2S-Wrapper(DTO)-Client Application. The communication between Client and Database is achieved by using Data Transfer Objects which contain entity objects as their properties. abstract public class BaseObject { public virtual IccSystem.iccObjectTypes ObjectICC_Type { get { return IccSystem.iccObjectTypes.unknownType; } } [global::System.Data.Linq.Mapping.ColumnAttribute(Storage = "_ID", AutoSync = AutoSync.OnInsert, DbType = "BigInt NOT NULL IDENTITY", IsPrimaryKey = true, IsDbGenerated = true)] [global::System.Runtime.Serialization.DataMemberAttribute(Order = 1)] public virtual long ID { //get; //set; get { return _ID; } set { _ID = value; } } } [DataContract] public class BaseObjectWrapper<T> where T : BaseObject { #region Fields private T _DBObject; #endregion #region Properties [DataMember] public T Entity { get { return _DBObject; } set { _DBObject = value; } } #endregion } Pretty simple, isn't it?. Here's the catch. Each one of the mapped classes contains ID property itself so I decided to override it like this [global::System.Data.Linq.Mapping.TableAttribute(Name="dbo.Divisions")] [global::System.Runtime.Serialization.DataContractAttribute()] public partial class Division : INotifyPropertyChanging, INotifyPropertyChanged { [global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_ID", AutoSync=AutoSync.OnInsert, DbType="BigInt NOT NULL IDENTITY", IsPrimaryKey=true, IsDbGenerated=true)] [global::System.Runtime.Serialization.DataMemberAttribute(Order=1)] public override long ID { get { return this._ID; } set { if ((this._ID != value)) { this.OnIDChanging(value); this.SendPropertyChanging(); this._ID = value; this.SendPropertyChanged("ID"); this.OnIDChanged(); } } } } Wrapper for division is pretty straightforward as well: public class DivisionWrapper : BaseObjectWrapper<Division> { } It worked pretty well as long as I kept ID values at mapped class and its BaseObject class the same(that's not very good approach, I know, but still) but then this happened: private CentralDC _dc; public bool UpdateDivision(ref DivisionWrapper division) { DivisionWrapper tempWrapper = division; if (division.Entity == null) { return false; } try { Table<Division> table = _dc.Divisions; var q = table.Where(o => o.ID == tempWrapper.Entity.ID); if (q.Count() == 0) { division.Entity._errorMessage = "Unable to locate entity with id " + division.Entity.ID.ToString(); return false; } var realEntity = q.First(); realEntity = division.Entity; _dc.SubmitChanges(); return true; } catch (Exception ex) { division.Entity._errorMessage = ex.Message; return false; } } When trying to enumerate over the in-memory query the following exception occurred: Class member BaseObject.ID is unmapped. Although I'm stating the type and overriding the ID property L2S fails to work. Any suggestions?

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• Design Patterns : Question about "Types"

  - by contactmatt

  Would someone please explain to me what the below paragraph means? This is a snippet from "Design Patterns: Elements of Reusable OO software" Part of an object's interface may be characterized by one type, and other parts by other types. Two objects of the same type need only share parts of their interfaces. Interfaces can contain other interfaces as subsets. - Design Patterns - Elements of Reusable OO software, pg 13

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• Android shared library which is not JNI based

  - by Mondain

  I am developing a library for Android applications which does not use native code (JNI). I have tried suppling the library as an external jar in my Android projects but this method does not include the library contents in the apk and thus throws class not found errors when run in the emulator or device. I have also tried creating the library as an Android project in itself and this does work, but only for public static properties (not methods). With the library and application both being in separate apk's I can see that the VM notices references to the library and can read some properties, but when an attempt to instantiate a class in the library is executed I get class not found even though I can read the public static properties from it (very frustrating!!). I realize that Davlik byte code is not the same as Java byte code but I am having trouble even finding good information about how to solve what would seem to be a very simple issue in Android. I am looking into the old PlatformLibrary stuff right now but I am not convinced this will work either since the sample has been removed from the Android site :( So help me out if you can, if I find the answer before this happens I will share it. viva la Android!

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• Master Detail same View binding controls

  - by pipelinecache

  Hi everyone, say I have a List View with ItemControls. And a Details part that shows the selected Item from List View. Both are in the same xaml page. I tried everything to accomplish it, but what do I miss? <!-- // List --> <ItemsControl ItemsSource="{Binding Path=Model, ElementName=SomeListViewControl, Mode=Default}" SnapsToDevicePixels="True" Focusable="False" IsTabStop="False"> <ItemsControl.ItemTemplate> <DataTemplate> <SomeListView:SomeListItemControl x:Name=listItem/> </DataTemplate> </ItemsControl.ItemTemplate> </ItemsControl> <!-- // Details --> <Label Content="Begindatum" FontSize="16" VerticalAlignment="Center" Grid.Row="1" Margin="2,0,0,0"/> <TextBox x:Name="Begindatum" Grid.Column="1" Grid.Row="1" Text="{Binding Path=BeginDate, ElementName=listItem,Converter={StaticResource DateTimeConverter}, ConverterParameter=dd-MM-yyyy}" IsEnabled="False" Style="{DynamicResource TextBoxStyle}" MaxLength="30"/> public event EventHandler<DataEventArgs<SomeEntity>> OnOpenSomething; public ObservableCollection<SomeEntity> Model { get { return (ObservableCollection<SomeEntity>)GetValue(ModelProperty); } set { Model.CollectionChanged -= new NotifyCollectionChangedEventHandler(Model_CollectionChanged); SetValue(ModelProperty, value); Model.CollectionChanged += new NotifyCollectionChangedEventHandler(Model_CollectionChanged); UpdateVisualState(); } } public static readonly DependencyProperty ModelProperty = DependencyProperty.Register("Model", typeof(ObservableCollection<SomeEntity>), typeof(SomeListView), new UIPropertyMetadata(new ObservableCollection<SomeEntity>(), new PropertyChangedCallback(ChangedModel))); private static void ChangedModel(DependencyObject source, DependencyPropertyChangedEventArgs e) { SomeListView someListView = source as SomeListView; if (someListView.Model == null) { return; } CollectionView cv = (CollectionView)CollectionViewSource.GetDefaultView(someListView.Model); } private void Model_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e) { if (Model == null) { return; } }

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