wpf 自定义控件绑定数据的数据传值

    public class BWlei : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        private int id;

        public int Id
        {
            get { return id; }
            set
            {
                id = value;
                if (PropertyChanged != null)
                {
                    PropertyChanged.Invoke(this, new PropertyChangedEventArgs("Id"));
                }
            }
        }

        private String xm = String.Empty;
        /// <summary>
        /// 姓名
        /// </summary>
        public String Xm
        {
            get { return xm; }
            set
            {
                xm = value;
                if (PropertyChanged != null)
                {
                    PropertyChanged.Invoke(this, new PropertyChangedEventArgs("Xm"));
                }
            }
        }

        private int xingBei = 0;
        /// <summary>
        /// 性别
        /// </summary>
        public int XingBei
        {
            get { return xingBei; }
            set
            {
                xingBei = value;
                if (PropertyChanged != null)
                {
                    PropertyChanged.Invoke(this, new PropertyChangedEventArgs("XingBei"));
                    PropertyChanged.Invoke(this, new PropertyChangedEventArgs("XingBeiImg"));
                }
            }
        }
        public Uri XingBeiImg
        {
            get
            {
                if (xingBei == 1)
                {
                    return new Uri("/TGHIS_Controls;component/Resources/nan60.jpg", UriKind.Relative);
                }
                else
                {
                    return new Uri("/TGHIS_Controls;component/Resources/nv60.jpg", UriKind.Relative);
                }
            }
        }

<UserControl x:Class="Controls.BW"
             xmlns="http://schemas. xmlns:x="http://schemas. xmlns:mc="http://schemas.
             xmlns:d="http://schemas.
             mc:Ignorable="d"
             d:DesignHeight="140" d:DesignWidth="90">
    <Button Name="bt_lb" Width="90" Height="140" Margin="0" Padding="0" Cursor="Hand" DataContext="{Binding}">
    <Button.Content>
    <Canvas Background="#eee" Width="90" Height="140">
                <Image Name="img_TuoXiang" Width="60" Height="60" Canvas.Left="0" Canvas.Top="0" Source="{Binding Path=XingBeiImg}"></Image>

                <TextBlock Name="tb_byxm" Canvas.Left="0" Canvas.Top="80" Width="90" Text="{Binding Path=Xm}" TextAlignment="Center" FontSize="16" FontWeight="Normal" FontFamily="NSimSun" Padding="2"></TextBlock>
            </Canvas>
        </Button.Content>
    </Button>
</UserControl>

    public partial class BW : UserControl
    {
        public BW()
        {
            InitializeComponent();
            bt_lb.DataContext = this.DataContext;
        }
    }

<UserControl x:Class="Controls.BiLB"
             xmlns="http://schemas. xmlns:x="http://schemas. xmlns:mc="http://schemas.
             xmlns:d="http://schemas.
             xmlns:myCon="clr-namespace:Controls"
             mc:Ignorable="d" >
    <ItemsControl  x:Name="itemsControl" ItemsSource="{Binding}">
        <ItemsControl.ItemsPanel>
            <ItemsPanelTemplate>
                <WrapPanel Orientation="Horizontal"/>
            </ItemsPanelTemplate>
        </ItemsControl.ItemsPanel>
        <ItemsControl.ItemTemplate>
            <DataTemplate>
                <Border Padding="3">
                    <WrapPanel>
                        <myCon:BW DataContext="{Binding BWlei}" Margin="10"/>
                    </WrapPanel>
                </Border>
            </DataTemplate>
        </ItemsControl.ItemTemplate>
    </ItemsControl>
</UserControl>

    public partial class BiLB : UserControl
    {
        public ObservableCollection<BWlei> bwList;
        public BiLB()
        {
            bwList = new ObservableCollection<BWlei>();
            InitializeComponent();
            itemsControl.ItemsSource = bwList;
        }
    }

        public MainWindow()
        {
            BiLB blb = new BiLB();
            WrapPanel_SFGL.Children.Add(blb);
        

            Dispatcher.BeginInvoke(DispatcherPriority.Background, (ThreadStart)delegate()
            {
                BWlei by = new BWlei();
                by.Id = 0;
                by.XingBei = 1;
                by.Xm= "11289111";
                blb.bwList.Add(by);
                BWlei by1 = new BWlei();
                by1.Id = 2;
                blb.bwList.Add(by1);
            });
}

    public partial class BW : UserControl
    {
        public BW()
        {
            InitializeComponent();
    断点此处   -->     bt_lb.DataContext = this.DataContext;  this.DataContext为NULL

        }
    }