Вячеслав Золотов

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:wpfApplication1="clr-namespace:WpfApplication1"
        Title="MainWindow" Height="350" Width="525">
    <Grid wpfApplication1:NewPropertyHelper.Prop="{Binding}">
        
    </Grid>
</Window>

namespace WpfApplication1
{
    public static class NewPropertyHelper
    {
        public static readonly DependencyProperty PropProperty = DependencyProperty.RegisterAttached("Prop", typeof (object), typeof (NewPropertyHelper), new PropertyMetadata(default(object)));

        public static object GetProp(UIElement element)
        {
            return (object) element.GetValue(PropProperty);
        }

        public static void SetProp(UIElement element, object value)
        {
            element.SetValue(PropProperty, value);
        }
    }
}