如何在静态类中绑定属性？

Question

I am making a WPF program by .net5 .

Here is my code:

public class ThemeBase:INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        void OnPropertyChanged(string name)=> PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));


        SolidColorBrush _PrimaryBackground;
        public SolidColorBrush PrimaryBackground
        {
            get => _PrimaryBackground;
            set { _PrimaryBackground = value;OnPropertyChanged("PrimaryBackground"); }
        }
Boolean _IsBlur;
        public Boolean IsBlur
        {
            get => _IsBlur;
            set {
                //some logic
            }
        }
}

And here is a subclass that inherits from it.

public class NormalWhite:ThemeBase
    {
        public NormalWhite() {
            PrimaryBackground = new SolidColorBrush(Colors.Red);
            IsBlur=false;
        }
    }

Finally, I set a static variable in a class named Global.cs :

public class Global
{
   public static Themes.ThemeBase Theme=new NormalWhite();
}

Here is the code in XAML:

<Border Background="{Binding Source=x:Static local:Global.Theme,Path=PrimaryBackground}">

After the program ran, the Binding Failure reports this error:

Severity    Count   Data Context    Binding Path    Target  Target Type Description File    Line    Project
Error   1   String  PrimaryBackground   Border.Background   Brush   PrimaryBackground property not found on object of type String.  \MainPage.xaml  23  Sample

Why I can't bind it?Thank you.

Answer 1

The Source expression must be Source={x:Static local:Global.Theme} - with braces:

<Border Background="{Binding Source={x:Static local:Global.Theme},
                             Path=PrimaryBackground}">

---

Since WPF 4.5 you can also bind directly to static properties.

Turn Theme into a property

public class Global
{
    public static Themes.ThemeBase Theme { get; set; } = new NormalWhite();
}

and bind to it with a path expression in parentheses:

<Border Background="{Binding Path=(local:Global.Theme.PrimaryBackground)}">

In case you want to change the Theme value at runtime, you must also implement a change notification, as eg shown here: https://stackoverflow.com/a/41823852/1136211