WPF

<Root 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns="clr-namespace:XamlBT.BT;assembly=XamlBT"    
    >
    
    <Root.Child>
        <Sequence>
                <Execute Function="{d:Binding StaticFuncs.Func}" />
        </Sequence>
    </Root.Child>
    
    <Root.Condition>
        <IfNot State="{d:Binding StaticFuncs.B}"/>
    </Root.Condition>
</Root>

public class Execute : DependencyObject, INode
    {
        public bool Evaluate()
        {
            if (Function != null)
            {
                    return Function();
            }
            return false;
        }

        public int Priority { get; set; }

        public Func<bool> Function
        {
            get { return (Func<bool>)GetValue(StateProperty); }
            set { SetValue(StateProperty, value); }
        }
        public static readonly DependencyProperty StateProperty = DependencyProperty.Register(
          "Function", typeof(Func<bool>), typeof(Execute), new PropertyMetadata(null));

    }