comboBox dropdownlist droplist 添加 value

public class ListItem
{
    private string _key = string.Empty;
    private string _value = string.Empty;
    public ListItem(string pKey, string pValue)
    {
        _key = pKey;
        _value = pValue;
    }
    public override string ToString()
    {
        return this._value;
    }
    public string Key
    {
        get
        {
            return this._key;
        }
        set
        {
            this._key = value;
        }
    }
    public string Value
    {
        get
        {
            return this._value;
        }
        set
        {
            this._value = value;
        }
    }
}


///////////////////////////////////////////////////////////////
comboBox1.Items.Add(new ListItem("请选择", "0"));
DataView dv = Comm.DB.ExecuteDataSet("select txtName,ID from dept where ParentID=24").Tables[0].DefaultView;
foreach (DataRowView drv in dv)
{
    comboBox1.Items.Add(new ListItem(drv["txtName"].ToString() , drv["ID"].ToString()));
}
comboBox1.DisplayMember = "Key";
comboBox1.ValueMember = "Value";
comboBox1.SelectedIndex = 0;

///////////////////////////////////////////////////////////////////
 MessageBox.Show(((ListItem)comboBox1.SelectedItem).Value);