Question

I am using WinRT XAML. I am trying to create my own HirarchicalDataTemplate in WinRT. I inherited my class from DataTemplate.

public class HierarchicalDataTemplate : DataTemplate
{}

But when I try to initialize a new HierarchicalDataTemplate in my Page resources, it shows following error on compilation.

HierarchicalDataTemplate does not contain a definition for ‘Template’.

Any ideas how to resolve.

Answer 1

The WinRT version of DataTemplate does not have a public Template property. The ContentProperty is specified as Template, so I tried changing that:

[ContentProperty(Name = "MyTemplate")]

However the error persists: the code generation tries to add an entry for the Template property all the same, from XamlTypeInfo.g.cs:

userType.AddMemberName("MyTemplate");
userType.AddMemberName("Template");

To use a different content property, we can either use a non DataTemplate subclass and define both Template and ItemTemplate of type DataTemplate; or continue to subclass DataTemplate, implement a dummy Template property, and use a separate MyTemplate property to host the actual content template. That might be usable at a push, but can’t allow the template to be used in a DataTemplate type property.

Trying to get a DataTemplate subclass to work, I tried adding a Template property of object type:

public class HierarchicalDataTemplate : DataTemplate
{
    public object Template
    {
        get { return (object)GetValue(TemplateProperty); }
        set { SetValue(TemplateProperty, value); }
    }
    public static readonly DependencyProperty TemplateProperty =
        DependencyProperty.Register("Template", typeof(object), typeof(HierarchicalDataTemplate), new PropertyMetadata(null));
    // ItemTemplate...
}

This works in the Visual Studio designer, but not at runtime:

<local:HierarchicalDataTemplate x:Key="t1">
    <TextBlock Text="SUCCESS" />
</local:HierarchicalDataTemplate>

From FrameworkTemplate docs:

FrameworkTemplate has a ContentPropertyAttribute that indicates that its XAML content property is named “Template”. FrameworkTemplate doesn’t define a property of that name, nor do its derived types that have a practical usage (ControlTemplate, DataTemplate). The content of a FrameworkTemplate is a root element that should be created when the template is applied, and isn’t a conventional property in the object model. Content of a FrameworkTemplate is handled specially by the XAML parser when content is created from a template.

It doesn’t look too hopeful.