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POMvvM with custom View-Elements. Data Binding problems
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copied!<p>As a newbie in Data-Binding, I don't know what I am doing wrong.</p> <ul> <li><p>I have some GUI elements defined in XAML, and I have data-binded them with appropriate ViewModels. So far so good.</p></li> <li><p>I also have some custom elements (geometrical shapes) that I place inside a Canvas (which Canvas I place inside the mainwindow through a user-control). I derived these entities from FrameworkElement, to have support for data-binding.</p></li> </ul> <p>So what I have done is to register some DependencyProperties and set the bindings to one of the existing ViewModels, as it seemed to me logical.</p> <p>Now the DependencyProperties of these custom classes, display some strange behaviour. </p> <p>i) When I keep the focus only on the Views (controls) that use the same ViewModel with the custom elements, the properties update normally. If I click everywhere else, the bindings break.</p> <p>ii) Sometimes, the Callback wasn't called although the property was changing.</p> <p>iii) When the StartupURI in App.xaml was the MainWindow, if I declared the ProfileV as a field (no matter where it was instantiated), the databinding mechanism worked in the way of (i). If it was declared inside the constructor, the mechanism didn't worked.</p> <p>What I am doing wrong, and what crucial thing i misunderstand about databinding ??</p> <pre class="lang-cs prettyprint-override"><code>class ProfileV : FrameworkElement, IGraphicalElement { public int SelectedTab { get { return (int)GetValue(SelectedTabProperty); } set { SetValue(SelectedTabProperty, value); } } public static readonly DependencyProperty SelectedTabProperty = DependencyProperty.Register("SelectedTab", typeof(int), typeof(ProfileV), new PropertyMetadata(new PropertyChangedCallback(CallBack))); public ProfileV(GeneralExecutionVM VM,CanvasV canvasV) { DataContext = VM; BindingOperations.SetBinding(this, SelectedTabProperty, new Binding("SelectedTab")); } public static void CallBack(DependencyObject d, DependencyPropertyChangedEventArgs e) { } } </code></pre> <p>Which binds with this</p> <pre class="lang-cs prettyprint-override"><code>public class GeneralExecutionVM : ObservableObject { private int _SelectedTab; public int SelectedTab { get { return _SelectedTab; } set { if (_SelectedTab == value) return; _SelectedTab = value; base.RaisePropertyChanged("SelectedTab"); } } } </code></pre> <p>(Observable Object, is the base class from the MVVM Foundation, of Josh Smith.) </p> <p><strong>ANSWERED</strong><br> OK i found it. The misconception here is about the <strong>DataContext</strong>.<br> Be careful when and where you set it, against setting an <strong>explicit source object</strong>. I misused it here, and caused a small chaotic situation.</p>

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