WPF Some styles not applied on DataTemplate controls

Question

I am trying to learn something about WPF and I am quite amazed by its flexibility.

However, I have hit a problem with Styles and DataTemplate

Answer 1

This is because ListBox is a logical parent of your datatemplate items, now remember, all properties those are "inheritable" like font, forecolor etc, are derived from the logical parent and ListBox already overrides it in its own default style, thats why this will not work. However in this case, you can use named styles as Mr. Dave has suggested, but I think if it does not work then this is a known problem in case of List Box etc, you can refere to my question here, i had similar problem in listbox, and the answers in my question are in more detail.

Answer 2

This is actually by design. Elements that do not derive from Control will not pick up implicit Styles, unless they are in the application resources.

This link explains this in more detail, or you can view the Connent bug report.

Answer 3

I discovered a simple workaround for this. For any elements that are not able to search outside the data template encapsulation boundary (i.e. are not being implicitly styled), you can just declare an empty style within the data template for that element type and use the BasedOn attribute of the style to find the correct implicit style outside the data template to apply.

In the example below, the TextBox is able to search outside the data template encapsulation boundary (because it inherits from Control?), but the TextBlock is not able to, so I declare the empty style for it which can search outside the data template.

<ItemsControl.ItemTemplate>
    <DataTemplate>
        <DataTemplate.Resources>
            <Style TargetType="TextBlock" BasedOn="{StaticResource {x:Type TextBlock}}" />
        </DataTemplate.Resources>
        <DockPanel>
            <TextBlock Text="{Binding Name}"  />
            <TextBox Text="{Binding Value}" />
        </DockPanel>
    </DataTemplate>
</ItemsControl.ItemTemplate>

Answer 4

I've looked into this also, and I personally think it's a bug. I've noticed that the style is set if you name your styles like so:

<Style x:Key="BorderStyle" TargetType="{x:Type Border}">
etc...

and explicitly set your DataTemplate to use those styles:

<HierarchicalDataTemplate DataTemplate="TestElement">
  <Border Height="45" Width="120" Margin="5,5", Style="{StaticResource BorderStyle}">

I think that it's possible that for DataTemplates (and maybe ControlTemplates), they default to having a null style, unless you explicitly set them.

That to me is not meant to happen - it's not a logical way of WPF working...