public partial class LabelText : UserControl
    {
        public static readonly DependencyProperty LabelTextProperty =
            DependencyProperty.Register(
            "LabelName", typeof(String),
            typeof(LabelText), null
            );
        public String LabelName
        {
            get { return (String)GetValue(LabelTextProperty); }
            set { SetValue(LabelTextProperty, value); }
        }
        public LabelText()
        {
            InitializeComponent();
//this.LabelName始终为NULL

        }
    }