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POWhy is my StackPanel not in the generated class? (NullReferenceException)
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  1. POWhy is my StackPanel not in the generated class? (NullReferenceException)
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    copied!<p>I'm getting a NullReferenceException in my code in the call to checkBox2_Checked. The exception indicates that stackPanelListbox is null. It's declared in the XAML, and a similarly declared stackPanel is not null. What is wrong here? </p> <p>Here's the XAML:</p> <pre><code>&lt;Window x:Class="ch0103.WPF.LayoutWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="LayoutWindow" Height="450" Width="900"&gt; &lt;StackPanel Name="stackPanelMain"&gt; &lt;WrapPanel&gt; &lt;CheckBox Name="checkBox1" VerticalAlignment="Center" IsThreeState="False" IsChecked="True" Click="checkBox_Checked" Content="Button StackPanel" Margin="0,0,11,0" /&gt; &lt;CheckBox Content="Listbox StackPanel" Height="16" Name="checkBox2" IsChecked="True" Checked="checkBox2_Checked" /&gt; &lt;/WrapPanel&gt; &lt;Grid Name="grid1" ShowGridLines="True"&gt; &lt;Grid.ColumnDefinitions&gt; &lt;ColumnDefinition Width="Auto" /&gt; &lt;ColumnDefinition /&gt; &lt;ColumnDefinition /&gt; &lt;/Grid.ColumnDefinitions&gt; &lt;StackPanel HorizontalAlignment="Left" Name="stackPanelButtons" VerticalAlignment="Top" Visibility="Visible"&gt; &lt;Button Content="Button" Height="23" Name="button1" /&gt; &lt;Button Content="Button" Height="23" Name="button2" /&gt; &lt;Button Content="Button" Height="23" Name="button3" /&gt; &lt;/StackPanel&gt; &lt;StackPanel Name="stackPanelListbox" Grid.Column="1"&gt; &lt;ListBox Grid.Column="2" HorizontalAlignment="Left" Name="listBox1" VerticalAlignment="Top" Width="200"&gt; &lt;ListBoxItem Content="Test" /&gt; &lt;ListBoxItem Content="Test" /&gt; &lt;ListBoxItem Content="Test" /&gt; &lt;ListBoxItem Content="Test" /&gt; &lt;ListBoxItem Content="Test" /&gt; &lt;ListBoxItem Content="Test" /&gt; &lt;ListBoxItem Content="Test" /&gt; &lt;/ListBox&gt; &lt;/StackPanel&gt; &lt;/Grid&gt; &lt;/StackPanel&gt; &lt;/Window&gt; </code></pre> <p>Here's the c# code: </p> <pre><code>using System.Windows; namespace ch0103.WPF { /// &lt;summary&gt; /// Interaction logic for LayoutWindow.xaml /// &lt;/summary&gt; public partial class LayoutWindow : Window { public LayoutWindow() { InitializeComponent(); } private void checkBox_Checked(object sender, RoutedEventArgs e) { stackPanelButtons.Visibility = (bool) checkBox1.IsChecked ? Visibility.Visible : Visibility.Collapsed; } private void checkBox2_Checked(object sender, RoutedEventArgs e) { stackPanelListbox.Visibility = (bool) checkBox2.IsChecked ? // stackPanelListbox is null here? Visibility.Visible : Visibility.Collapsed; } } } </code></pre>
 

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