问无法通过反射获取WPF附加属性

EN

public class Freezable
{
    public static bool GetIsFrozen(DependencyObject obj)
    {
        return (bool)obj.GetValue(IsFrozenProperty);
    }

    public static void SetIsFrozen(DependencyObject obj, bool value)
    {
        obj.SetValue(IsFrozenProperty, value);
    }

    public static readonly DependencyProperty IsFrozenProperty =
        DependencyProperty.RegisterAttached("IsFrozen", typeof(bool), typeof(UIElement), new UIPropertyMetadata(false));
}

Freezable.SetIsFrozen(control, value);
var correctValue =Freezable.GetIsFrozen(control);

 public void FindAttachedProperty(Type elementType, string propertyName)
    {
        MethodInfo getMethod = elementType.GetMethod("Get" + propertyName, BindingFlags.Public | BindingFlags.Static);
        MethodInfo setMethod = elementType.GetMethod("Set" + propertyName, BindingFlags.Public | BindingFlags.Static);
    }