Custom WPF Binding

Question

I have a custom MarkupExtension that simulates binding. It works well in normal assignments but when used in Style Setters, for example:

Answer 1

From the documentation, it looks like the object must be freezable (so they can be shared between various interested parties)

http://msdn.microsoft.com/en-us/library/system.windows.setter.value.aspx

"Data binding and dynamic resources within the object is supported if the specified value is a Freezable object. See Binding Markup Extension and DynamicResource Markup Extension."

Answer 2

why don't you

return Value

inside the ProvideValue??

else

You can bind to only DependencyProperty. make a dependency property for Value in your MyExtension Class!

public static readonly DependencyProperty ValueProperty = DependencyProperty.Register("Value", typeof(Object), typeof(MyContentControl), new UIPropertyMetadata());

Answer 3

Kind of guessing, but it's likely because the XAML compiler has special built-in support for the Binding class, allowing its usage in this scenario (and others). The Binding class is also a MarkupExtension, but unfortunately it seals its implementation of ProvideValue().

That said, you might just get away with this:

public class MyBinding : Binding
{
    private object value;

    public object Value
    {
        get { return this.value; }
        set
        {
            this.value = value;
            this.Source = value;
        }
    }
}

Since ProvideValue will return the Binding instance anyway.