OK, my solution was totally unnecessary, here are the only tutorials you will ever need for creating any user control:
In short:
Subclass some suitable class (or UIElement if none suits you) - the file is just plain *.cs, as we are only defining the behaviour, not the looks of the control.
public class EnhancedItemsControl : ItemsControl
Add dependency property for your 'slots' (normal property is not good enough as it has only limited support for binding). Cool trick: in VS, write propdp and press tab to expand the snippet :):
public object AlternativeContent
{
get { return (object)GetValue(AlternativeContentProperty); }
set { SetValue(AlternativeContentProperty, value); }
}
// Using a DependencyProperty as the backing store for AlternativeContent. This enables animation, styling, binding, etc...
public static readonly DependencyProperty AlternativeContentProperty =
DependencyProperty.Register("AlternativeContent" /*name of property*/, typeof(object) /*type of property*/, typeof(EnhancedItemsControl) /*type of 'owner' - our control's class*/, new UIPropertyMetadata(null) /*default value for property*/);
Add an attribute for a designer (because you are creating so-called lookless control), this way we say that we need to have a ContentPresenter called PART_AlternativeContentPresenter in our template
[TemplatePart(Name = "PART_AlternativeContentPresenter", Type = typeof(ContentPresenter))]
public class EnhancedItemsControl : ItemsControl
Provide a static constructor that will tell to WPF styling system about our class (without it, the styles/templates that target our new type would not be applied):
static EnhancedItemsControl()
{
DefaultStyleKeyProperty.OverrideMetadata(
typeof(EnhancedItemsControl),
new FrameworkPropertyMetadata(typeof(EnhancedItemsControl)));
}
If you want to do something with the ContentPresenter from the template, you do it by overriding the OnApplyTemplate method:
//remember that this may be called multiple times if user switches themes/templates!
public override void OnApplyTemplate()
{
base.OnApplyTemplate(); //always do this
//Obtain the content presenter:
contentPresenter = base.GetTemplateChild("PART_AlternativeContentPresenter") as ContentPresenter;
if (contentPresenter != null)
{
// now we know that we are lucky - designer didn't forget to put a ContentPresenter called PART_AlternativeContentPresenter into the template
// do stuff here...
}
}
Provide a default template: always in ProjectFolder/Themes/Generic.xaml (I have my standalone project with all custom universally usable wpf controls, which is then referenced from other solutions). This is only place where system will look for templates for your controls, so put default templates for all controls in a project here:
In this snippet I defined a new ContentPresenter that displays a value of our AlternativeContent attached property. Note the syntax - I could use either
Content="{Binding AlternativeContent, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type WPFControls:EnhancedItemsControl}}}" or Content="{TemplateBinding AlternativeContent}", but the former will work if you define a template inside your template (necessary for styling for example ItemPresenters).
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:WPFControls="clr-namespace:MyApp.WPFControls"
>
<!--EnhancedItemsControl-->
<Style TargetType="{x:Type WPFControls:EnhancedItemsControl}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type WPFControls:EnhancedItemsControl}">
<ContentPresenter
Name="PART_AlternativeContentPresenter"
Content="{Binding AlternativeContent, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type WPFControls:EnhancedItemsControl}}}"
DataContext="{Binding DataContext, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type WPFControls:EnhancedItemsControl}}}"
/>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</ResourceDictionary>
Voila, you just made your first lookless UserControl (add more contentpresenters and dependency properties for more 'content slots').