<Window x:Class="WpfApplication53.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:WpfApplication53"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <TextBox Text="{Binding Path=XPropety, Source={x:Static local:AClass.Instance}}" />
    </Grid>
</Window>

using System.Windows;

namespace WpfApplication53
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            AClass.Instance.XPropety = "ABC";

            InitializeComponent();
        }
    }

    public class AClass
    {
        public static AClass Instance = new AClass();

        public string XPropety { get; set; }
    }
}