WPF 自定义控件依赖属性绑定

自定义一个简单控件，添加依赖属性，想在xmal中绑定设置依赖属性的值，绑定不起作用求问是怎么回事？

 public partial class LabelEx : UserControl
    {
        public LabelEx()
        {
            InitializeComponent();
            Data = "000";
            this.DataContext = this;
        }


        public static readonly DependencyProperty DataProperty = DependencyProperty.Register(
                    "Data", typeof(string), typeof(LabelEx), new FrameworkPropertyMetadata(""));

        public string Data
        {
            get { return (string)GetValue(DataProperty);}
            set {  SetValue(DataProperty, value);}
        }


        public string Title
        {
            get { return title.Text; }
            set { title.Text = value; }
        }
    }

如果将控件属性绑定到Data上能正常工作，如下代码：

 <src:LabelEx Data="{Binding Text, ElementName=txt}"></src:LabelEx>

但是我想绑定到对象属性上就不能正常工作，绑定不起作用,前台xmal代码：

 <src:LabelEx Data="{Binding XName}"></src:LabelEx>

后台CS代码

```public partial class Window1 : Window, INotifyPropertyChanged
{
private float? age;

    public float? Age
    {
        get { return age; }
        set { age = value; NotifyPropertyChanged("Age"); }
    }

    private float? score;

    public float? Score
    {
        get { return score; }
        set { score = value; NotifyPropertyChanged("Score"); }
    }

    private string xname;
    public string XName
    {
        get { return xname; }
        set { xname = value; NotifyPropertyChanged("XName"); }
    }

    public Window1()
    {
        InitializeComponent();
        this.DataContext = this;
        xname = "1234";
        age = 60;
        score = 380;
    }

http://blog.csdn.net/lanpst/article/details/19406331

我去，我改了一天bug，终于发现UserControl去掉DataContext=this;就可以了