Cannot bind to public property inside ResourceDirectory WinUI3/UWP

Question

So I am currently trying to bind a public static SolidColorBrush to a "Filled" property on a Rectangle inside a ResourceDirectory Style (inisde App.xaml). But I always get the Exception

"Type 'x' used after '{' must be a Markup Extention. Error code 0x09c6."

My xaml code looks like this (inside App.xaml):

<Rectangle
    x:Name="SelectionIndicator"
    Width="4"
    Height="24"
    Fill="{x:Bind SomeNamespace:SomeClass.SomeColor}"/>

and my codebehind looks like this (inside public class called "SomeClass" in Namespace called "SomeNamespace"):

public static SolidColorBrush SomeColor = new(Colors.Red);

I know its possible to bind to a public static property with x:Bind in WinUI/UWP but this somehow doesnt work. I really need to bind from some code behind so I can implement INotifyPropertyChanged so I cant just create a new color resource. What is the correct way to implement my wanted behavior? Thanks in advance!

Answer 1

You probably can't call your PropertyChanged event handler from a static property. You'll need an instance.

Consider storing the brush as a non-static property in a wrapper class. You can instantiate this class as a resource in your App.xaml file and use it across your application.

ColorStorer is a class to store the SolidColorBrush:

public class ColorStorer: INotifyPropertyChanged
{
    private SolidColorBrush scb = new SolidColorBrush(Colors.Red);
    public SolidColorBrush Scb
    {
        get
        {
            return scb;
        }

        set
        {
            if (value as SolidColorBrush != null)
            {
                scb = value;
                NotifyPropertyChanged();
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    public void NotifyPropertyChanged([CallerMemberName] string name = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
    }
}

Instantiate it in Application.Resources in App.xaml:

<Application.Resources>
    <ResourceDictionary>
        <local:ColorStorer x:Key="TestAppColorStorer" />
    </ResourceDictionary>
</Application.Resources>

Use it in your views and controls:

<Rectangle
            Width="100"
            Height="50"
            HorizontalAlignment="Center"
            Fill="{Binding Scb, Source={StaticResource TestAppColorStorer}, Mode=OneWay}" />