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POListView.ItemContainerGenerator.ContainerFromItem(item) return null after 20 items
 

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  1. POListView.ItemContainerGenerator.ContainerFromItem(item) return null after 20 items
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    <p>first of all I want to explain what I'm trying to do. I have a <code>ListView</code> in a <code>UserControl</code> with a <code>DataTemplate</code> defined as a resource. I want to hide a button inside the DataTemplate. Sounds easy, but ....</p> <p>The code I'm using is </p> <pre><code>&lt;UserControl.Resources&gt; &lt;DataTemplate x:Key="Proyectos"&gt; &lt;DockPanel Name="Panel" Margin="0,0,0,0" MinWidth="1200" MaxWidth="1200"&gt; &lt;Border Margin="0" BorderBrush="Bisque" BorderThickness="1" DockPanel.Dock="Left"&gt; &lt;StackPanel Margin="0" Width="1135"&gt; &lt;DockPanel&gt; &lt;TextBlock Text="{Binding titulo}" Name="titulo" FontWeight="Bold" FontSize="12" /&gt; &lt;/DockPanel&gt; &lt;DockPanel &gt; &lt;TextBlock FontWeight="Bold" Text="Nº Ref. Fundacion: " DockPanel.Dock="Left" Margin="5,0,5,0" FontSize="11"/&gt; &lt;TextBlock Name="txb_codproy" Text="{Binding codproy}" FontSize="11"/&gt; &lt;TextBlock FontWeight="Bold" Text=" Nº Ref. Proyecto: " FontSize="11"/&gt; &lt;TextBlock Text="{Binding registro}" FontSize="11"/&gt; &lt;TextBlock FontWeight="Bold" Text=" Estado: " FontSize="11"/&gt; &lt;TextBlock Text="{Binding estados_proyecto.descripcion}" FontSize="11"/&gt; &lt;/DockPanel&gt; &lt;DockPanel &gt; &lt;TextBlock FontWeight="Bold" Text="Organismo " DockPanel.Dock="Left" Margin="5,0,5,0" FontSize="11"/&gt; &lt;TextBlock Text="{Binding organismo.descripcion}" FontSize="11"/&gt; &lt;/DockPanel&gt; &lt;/StackPanel&gt; &lt;/Border&gt; &lt;Border Margin="0" Width="Auto" BorderBrush="Transparent" BorderThickness="1" Background="White" HorizontalAlignment="Left"&gt; &lt;Button Margin="0,0,0,0" VerticalAlignment="Center" HorizontalAlignment="Left" Name="btn_Eliminar" Click="btn_Eliminar_Click" Width="Auto" Height="25" Background="Transparent" BorderBrush="Transparent"&gt; &lt;Image Name="img_eliminar" Width="48" Source="imagenes/borrar.png" Height="19" /&gt; &lt;/Button&gt; &lt;/Border&gt; &lt;/DockPanel&gt; &lt;/DataTemplate&gt; &lt;/UserControl.Resources&gt; &lt;Grid Width="1300" Height="845.169"&gt; &lt;ListView Margin="20,120.024,15.247,50" MouseDoubleClick="list_proyectos_MouseDoubleClick" Name="list_proyectos" ItemsSource="{Binding}" ItemTemplate="{StaticResource Proyectos}"&gt; &lt;/ListView&gt; &lt;TextBox Margin="32,12,35,0" Name="txt_busqueda" TextChanged="textBox1_TextChanged" Background="AliceBlue" BorderBrush="Gray" Height="23" VerticalAlignment="Top" /&gt; &lt;/Grid&gt; ////////////////////////////////////////////////////////// public Proyectos(IPrincipal identityA) { list_proyectos.ItemsSource = ListaProyectos; list_proyectos.ItemContainerGenerator.StatusChanged += new EventHandler(ItemContainerGenerator_StatusChanged); } void ItemContainerGenerator_StatusChanged(object sender, EventArgs e) { if (list_proyectos.ItemContainerGenerator.Status == System.Windows.Controls.Primitives.GeneratorStatus.ContainersGenerated) { list_proyectos.ItemContainerGenerator.StatusChanged -= ItemContainerGenerator_StatusChanged; Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.Input, new VoidDelegate(DelayedAction)); } } delegate void VoidDelegate(); void DelayedAction() { foreach (object item in list_proyectos.Items) { ListBoxItem lbitem = (ListBoxItem)list_proyectos.ItemContainerGenerator.ContainerFromItem(item); if (lbitem != null) { ContentPresenter contentPresenter = FindVisualChild&lt;ContentPresenter&gt;(lbitem); DataTemplate myDataTemplate = contentPresenter.ContentTemplate; Button b = (Button)lbitem.ContentTemplate.FindName("btn_Eliminar", contentPresenter); b.Visibility = Visibility.Hidden; } } } private T FindVisualChild&lt;T&gt;(DependencyObject obj) where T : DependencyObject { for (int i = 0; i &lt; VisualTreeHelper.GetChildrenCount(obj); i++) { DependencyObject child = VisualTreeHelper.GetChild(obj, i); if (child != null &amp;&amp; child is T) return (T)child; } for (int i = 0; i &lt; VisualTreeHelper.GetChildrenCount(obj); i++) { DependencyObject child = VisualTreeHelper.GetChild(obj, i); T childOfChild = FindVisualChild&lt;T&gt;(child); if (childOfChild != null) return childOfChild; } return null; } </code></pre> <p>I found two problems with this, </p> <ol> <li><p>This line <code>(ListBoxItem)list_proyectos.ItemContainerGenerator.ContainerFromItem(item);</code> returns null after the 16th item. The listview has 1576 items</p></li> <li><p>When the ListView is shown and the first 16 items have the button hidden, if I scroll down to the end and then go to top again the buttons are visible again.</p></li> </ol>
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    1. COYour code sample looks over complicated for what you're trying to do. Could you please try to explain what is the behavior you want in your ListView ?
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