WinForm ComboBox 数据绑定问题。

[Allblus]

我想把下面代码中类CAxisItem的属性 PulseDirection 双向绑定到一个 comboBox1上面去，使comboBox1里面有“”正向、反向“”的选项，他的值的改变跟对象AxisItem属性PulseDirection 相互对应，怎么搞啊？
就是下面代码中打问号的部分怎么弄？谢谢了。

=============================

public enum E_DIRECTION
    {
        DEFAULT,
        INVERSE
    }

public class CAxisItem : INotifyPropertyChanged
{
        public event PropertyChangedEventHandler PropertyChanged;

        private E_DIRECTION pulse_direction;
        public E_DIRECTION PulseDirection
        {
            get
            {
                return pulse_direction;
            }
            set
            {
                if (pulse_direction != value)
                {
                    pulse_direction = value;
                    if (PropertyChanged != null)
                    {
                        PropertyChanged(this, new PropertyChangedEventArgs("PulseDirection"));
                    }
                }
            }
        }

}

public partial class Form1 : Form
{ 
        private BindingList<string> DirectionList = new BindingList<string>();
        public BindingList<string> BindingDirectionList
        {
            get
            {
                return DirectionList;
            }
        }

    public Form1()
    {
            InitializeComponent();
            DirectionList.Add("正向");
            DirectionList.Add("反向");

             CAxisItem AxisItem = new CAxisItem();
            ///???????????????????????????????????????????????
            Binding B = new Binding("SelectedItem", AxisItem, "PulseDirection", false, DataSourceUpdateMode.OnPropertyChanged);
            comboBox1.DataBindings.Add(B);

            B = new Binding("SelectedValue", AxisItem, "PulseDirection", false, DataSourceUpdateMode.OnPropertyChanged);
            comboBox1.DataBindings.Add(B);
            ///???????????????????????????????????????????????
    }

}

[Allblus]

             Binding Bb = new Binding("SelectedItem", this, "BindingDirectionList", false, DataSourceUpdateMode.OnPropertyChanged);
            comboBox1.DataBindings.Add(Bb);

            Binding Bc = new Binding("SelectedValue", AxisItem, "PulseDirection", false, DataSourceUpdateMode.OnPropertyChanged);
            comboBox1.DataBindings.Add(Bc);

这样也不行，comboBox1中什么也没有。

[Allblus]

兄弟们，消灭零回复啊。