How can I set style to derived control?

[kyuranger]

I want to add a custom property to some usercontrols. So, I created a base class and all the usercontrol will be inherited from the baseclass for convenience.

Here is my code:

using Avalonia;
using Avalonia.Controls;
using Avalonia.Media;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace AvaloniaApplication1
{
    public class BaseClass:UserControl
    {
        public static readonly StyledProperty<IBrush> CustomForegroundProperty =
     AvaloniaProperty.Register<BaseClass, IBrush>(nameof(CustomForeground), new SolidColorBrush(Colors.Red));

        public IBrush CustomForeground
        {
            get { return GetValue(CustomForegroundProperty); }
            set { SetValue(CustomForegroundProperty, value); }
        }
    }
}

And here is a sample usercontrol:

<Local:BaseClass xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
			 xmlns:Local="using:AvaloniaApplication1"
             x:Class="AvaloniaApplication1.UserControl1">
	<Grid>
		<TextBlock Foreground="{Binding CustomForeground,RelativeSource={RelativeSource AncestorType={x:Type Local:BaseClass}}}">123</TextBlock>
	</Grid>
</Local:BaseClass>

using Avalonia;
using Avalonia.Controls;
using Avalonia.Markup.Xaml;

namespace AvaloniaApplication1;

public partial class UserControl1 : BaseClass
{
    public UserControl1()
    {
        InitializeComponent();
    }
}

And it works well.

Now I want to set style to all the control that inherit from BaseClass:

<Window xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
        x:Class="AvaloniaApplication1.MainWindow"
		xmlns:Local="using:AvaloniaApplication1"
        Title="AvaloniaApplication1">
	<Window.Styles>
		<Style Selector="Local|BaseClass">
			<Setter Property="CustomForeground" Value="Green"></Setter>
		</Style>
	</Window.Styles>
	<Local:UserControl1>
		
	</Local:UserControl1>
</Window>

As the image above, the style doesn't work any. It still is the default color but not the green color I set it in style.

What's wrong with my code?

[maxkatz6]

You likely need a :is(Local|BaseClass).
Because in case of UserControl1 styled key name is UserControl1 now, not the BaseClass.

[kyuranger]

It works! Thank you very much, I learned more.

[james1301]

You likely need a :is(Local|BaseClass). Because in case of UserControl1 styled key name is UserControl1 now, not the BaseClass.

Hi I don't quite understand where you put that code?

[thevortexcloud]

The docs for it are here:

https://docs.avaloniaui.net/docs/reference/styles/style-selector-syntax#include-derived-classes

[perfectphase]

Thank you! You wouldn't believe how long it took that penny to drop! :)

[thevortexcloud]

Glad I could help.