creating custom itemscontrol

Question

I'm trying to create a custom control derived from ItemsControl. The ItemsControl is initialized with items, but they are not shown.

the itemsControl :

public class PipeControl : ItemsControl 
{
    static PipeControl()
    {
        DefaultStyleKeyProperty.OverrideMetadata(typeof(PipeControl), new FrameworkPropertyMetadata(typeof(PipeControl)));                    
    }

    public PipeControl()
    {
        Checkers = new ObservableCollection<Checker>();
        Checkers.Add(new Checker());
        Checkers.Add(new Checker());
        Checkers.Add(new Checker());
        Checkers.Add(new Checker());
        Checkers.Add(new Checker());           
    }

    public ObservableCollection<Checker> Checkers 
    {
        get;
        set;               
    }        
}    

the themes resource dictionary : Generic.xaml

<Style TargetType="{x:Type local:PipeControl}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type local:PipeControl}">
                <Border Background="{TemplateBinding Background}"
                        BorderBrush="{TemplateBinding BorderBrush}"
                        BorderThickness="{TemplateBinding BorderThickness}">                                        
                </Border>
            </ControlTemplate>
        </Setter.Value>
    </Setter>

    <Setter Property="ItemTemplate">
        <Setter.Value>
            <DataTemplate DataType="{x:Type local:Checker}">
                <Ellipse Fill="Red" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" />                    
            </DataTemplate>                
        </Setter.Value>            
    </Setter>

    <Setter Property="ItemsSource" Value="{Binding Checkers,RelativeSource={RelativeSource Self}}"/>                           

    <!-- Just a Precaution its the default panel any ways -->  
    <Setter Property="ItemsPanel">
        <Setter.Value>
            <ItemsPanelTemplate>
                <StackPanel />
            </ItemsPanelTemplate>
        </Setter.Value>            
    </Setter>

</Style>

Any ideas why the items are not shown?

Answer 1

You need to set the ItemsSource. So, for example, you could add ItemsSource = Checkers; below the last Checkers Add line. Even though you're trying to set the ItemsSource to Checkers in the style, I think it would be easier if you set in the control class. Just my two cents, though.

Here's an example of the PipeControl class:

public class PipeControl : ItemsControl
{
    public ObservableCollection<Checker> Checkers { get; set; }
    static PipeControl()
    {
        DefaultStyleKeyProperty.OverrideMetadata(typeof(PipeControl), new FrameworkPropertyMetadata(typeof(PipeControl)));
    }
    public PipeControl()
    {
        Checkers = new ObservableCollection<Checker>();
        Checkers.Add(new Checker());
        Checkers.Add(new Checker());
        Checkers.Add(new Checker());
        Checkers.Add(new Checker());
        Checkers.Add(new Checker());
        ItemsSource = Checkers;
    }
}

You also need an ItemsPresenter in your ControlTemplate and your Ellipse needs a width and height. Here's an updated style for you:

<Style TargetType="{x:Type local:PipeControl}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type local:PipeControl}">
                <Border Background="{TemplateBinding Background}"
                        BorderBrush="{TemplateBinding BorderBrush}"
                        BorderThickness="{TemplateBinding BorderThickness}">
                    <ItemsPresenter />
                </Border>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
    <Setter Property="ItemTemplate">
        <Setter.Value>
            <DataTemplate DataType="{x:Type local:Checker}">
                <Ellipse Width="25"
                         Height="25"
                         HorizontalAlignment="Stretch"
                         VerticalAlignment="Stretch"
                         Fill="Red" />
            </DataTemplate>
        </Setter.Value>
    </Setter>
    <Setter Property="ItemsPanel">
        <Setter.Value>
            <ItemsPanelTemplate>
                <StackPanel Orientation="Horizontal" />
            </ItemsPanelTemplate>
        </Setter.Value>
    </Setter>
</Style>