SL2: ItemsControl and nested FrameworkElements

05-18-2009 11:22 AM |

 I have extended the ItemsControl to have also an header, but when I add an FrameworkElement as child, which should displayed in the header, SL2 crash.

The header is rendered as a button, so the end design should be a FrameworkElement, for example a TextBlock, inside a Button. At the end of the Page I have added also a Button with inside a TextBox, which is rendered without problems. Why inside the ItemsControl it crashes?

 Thanks in advance for any help.

 Page xaml

<UserControl x:Class="SilverlightApplication18.Page"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:sys="clr-namespace:System;assembly=mscorlib"
    xmlns:local="clr-namespace:SilverlightApplication18"         
    Width="400" Height="300">
    <StackPanel x:Name="LayoutRoot" Background="White">
        <local:ItemsControlTest Header="Test">
            <sys:String>Test1</sys:String>
            <local:ItemsControlTest Header="Test2">
                <sys:String>Test3</sys:String>
            </local:ItemsControlTest>
            <!--<TextBox />--> <!-- This FrameworkElement crashes SL -->
        </local:ItemsControlTest>
        <Button HorizontalAlignment="Left" VerticalAlignment="Top">
            <TextBox />
        </Button>
    </StackPanel>
</UserControl>

 ItemsControlTest.cs

namespace SilverlightApplication18
{
    public class ItemsControlTest : ItemsControl
    {
        public static readonly DependencyProperty HeaderProperty = DependencyProperty.Register("Header", typeof(object), typeof(ItemsControlTest), null);

        public ItemsControlTest()
        {
            this.DefaultStyleKey = typeof(ItemsControlTest);
        }

        public object Header
        {
            get { return base.GetValue(ItemsControlTest.HeaderProperty); }
            set { base.SetValue(ItemsControlTest.HeaderProperty, value); }
        }

        protected override DependencyObject GetContainerForItemOverride()
        {
            return new ItemsControlTest();
        }

        protected override bool IsItemItsOwnContainerOverride(object item)
        {
            return item is ItemsControlTest;
        }

        protected override void PrepareContainerForItemOverride(DependencyObject element, object item)
        {
            ItemsControlTest test = element as ItemsControlTest;
            if (test != null && item != null && item != test)
            {
                test.Header = item;
                //test.Header = new TextBox(); //Adding a new FrameworkElement doesn't crash SL
            }
            //base.PrepareContainerForItemOverride(element, item);
        }
    }
}

Themes/Generic.xaml

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:vsm="clr-namespace:System.Windows;assembly=System.Windows"
    xmlns:local="clr-namespace:SilverlightApplication18">
    <Style TargetType="local:ItemsControlTest">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="local:ItemsControlTest">
                    <StackPanel>
                        <Button Content="{TemplateBinding Header}" />
                        <ItemsPresenter Margin="10,0,0,0" />
                    </StackPanel>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>