1.下拉框声明

<ComboBox x:Name="DirComboBox" Width="150" Height="18" Margin="6,0,0,0">
</ComboBox>

　　2. 初始化下拉框

/// <summary>
/// 初始化下拉框
/// </summary>
public void SetDirComboBox()
{
DirComboBox.ItemsSource = SessionHelper.Context.DirList;
DirComboBox.SelectedValuePath = "oid";
DirComboBox.DisplayMemberPath = "name";
DirComboBox.SelectedIndex = 0;
SessionHelper.Context.DirComboBox = DirComboBox;
}

　　注：Context中

public ObservableCollection<MetaDirVO> DirList = newObservableCollection<MetaDirVO>();
public ComboBox DirComboBox { get; set; }

　　3.当DirList新增时，更新ComboBox 的ItemsSource ，并设置默认值：

SessionHelper.Context.DirList.Insert(0,new MetaDirVO(tvs.Id, tvs.Name));
SessionHelper.Context.DirComboBox.ItemsSource =

SessionHelper.Context.DirList;
SessionHelper.Context.DirComboBox.SelectedIndex = 0;

　　4. 用到的VO：

public class MetaDirVO :AbstractModel
{
public MetaDirVO(string oid, string name)
{
this.oid = oid;
this.name = name;
}
public string oid { get; set; }
public string name { get; set ; }
...
}