How to use default styles for controls as base for custom styles without copying

[Balkoth]

For controls from Microsoft.UI.Xaml.Controls we can just use something like this in our styles and call it a day:

<Style
  x:Key="NoSpellCheckTextBoxStyle"
  BasedOn="{StaticResource DefaultTextBoxStyle}"
  TargetType="TextBox">
  <Setter Property="IsSpellCheckEnabled" Value="False" />
</Style>

How can we use styles from this library without copying the default style into our resources first? To my knowledge this does not work:

<Style
  x:Key="MyHeaderedContentControlStyle"
  BasedOn="{StaticResource DefaultHeaderedContentControlStyle}"
  TargetType="wuic:HeaderedContentControl">
  <Setter Property="HorizontalAlignment" Value="Stretch" />
  <Setter Property="HorizontalContentAlignment" Value="Stretch" />
  <Setter Property="VerticalContentAlignment" Value="Stretch" />
  <Setter Property="IsTabStop" Value="False" />
</Style>

While DefaultHeaderedContentControlStyle is a valid style from this library, using it like this crashes when trying to load a control with the custom style.

I guess we can agree that simply copying styles is not the way to approach this, because then we would have to track all changes done to the default style and reapply them when necessary. Is it possible for this library to expose the styles like Microsoft.UI.Xaml.Controls does or am i missing something here?

[AndrewKeepCoding]

You need to merge the resource file.

App.xaml

<Application
    x:Class="WinUIDemoApp.App"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:WinUIDemoApp">
    <Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <XamlControlsResources xmlns="using:Microsoft.UI.Xaml.Controls" />
                <!--  Other merged dictionaries here  -->
                <ResourceDictionary Source="ms-appx:///CommunityToolkit.WinUI.Controls.HeaderedControls/HeaderedContentControl/HeaderedContentControl.xaml" />
            </ResourceDictionary.MergedDictionaries>
            <!--  Other app resources here  -->
        </ResourceDictionary>
    </Application.Resources>
</Application>

[Balkoth]

I knew i was missing something. Either way it would be nice if the control packages could expose something along the lines:

<Application
  x:Class="My.App"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  xmlns:ctrls="using:Microsoft.UI.Xaml.Controls"
  xmlns:wuic="using:CommunityToolkit.WinUI.Controls">
  <Application.Resources>
    <ResourceDictionary>
      <ResourceDictionary.MergedDictionaries>
        <ctrls:XamlControlsResources />

        <!-- Not like this -->        
        <!--<ResourceDictionary Source="ms-appx:///CommunityToolkit.WinUI.Controls.HeaderedControls/HeaderedContentControl/HeaderedContentControl.xaml" />-->

        <!-- This would be much more discoverable and inline with how WinUI3 does it -->
        <wuic:HeaderedControlsResources />
        <wuic:SettingsControlsResources />

      </ResourceDictionary.MergedDictionaries>
    </ResourceDictionary>
  </Application.Resources>
</Application>

[ghost1372]

I knew i was missing something. Either way it would be nice if the control packages could expose something along the lines:

<Application
  x:Class="My.App"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  xmlns:ctrls="using:Microsoft.UI.Xaml.Controls"
  xmlns:wuic="using:CommunityToolkit.WinUI.Controls">
  <Application.Resources>
    <ResourceDictionary>
      <ResourceDictionary.MergedDictionaries>
        <ctrls:XamlControlsResources />

        <!-- Not like this -->        
        <!--<ResourceDictionary Source="ms-appx:///CommunityToolkit.WinUI.Controls.HeaderedControls/HeaderedContentControl/HeaderedContentControl.xaml" />-->

        <!-- This would be much more discoverable and inline with how WinUI3 does it -->
        <wuic:HeaderedControlsResources />
        <wuic:SettingsControlsResources />

      </ResourceDictionary.MergedDictionaries>
    </ResourceDictionary>
  </Application.Resources>
</Application>

Adding the resource dictionary like <wuic:HeaderedControlsResources/> will break IntelliSense.

[Balkoth]

Defining it like <ResourceDictionary Source="ms-appx:///CommunityToolkit.WinUI.Controls.HeaderedControls/HeaderedContentControl/HeaderedContentControl.xaml" /> the DefaultHeaderedContentControlStyle style also does not show up in IntelliSense.

[AndrewKeepCoding]

Actually, what @Balkoth is suggesting (IntelliSense support) is not difficult. Adding this class in the project should do:

HeaderedControlsResources.cs

namespace CommunityToolkit.WinUI.Controls;

public sealed partial class HeaderedControlsResources : ResourceDictionary
{
    public HeaderedControlsResources()
    {
        this.Source = new Uri("ms-appx:///HeaderedControls/Themes/Generic.xaml");
    }
}

Then in the app project we'll just need to merge it:

App.xaml

<toolkit:HeaderedControlsResources />

FYI @Arlodotexe @michael-hawker