<Window x:Class="Demo.MainWindow"

         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

         Title="MainWindow" Height="350" Width="525" DataContext="{Binding}">

     <Grid>

         <TextBlock Height="23" HorizontalAlignment="Left" Margin="27,41,0,0" Name="textBlock1" Text="省" VerticalAlignment="Top" />

         <ComboBox Height="23" HorizontalAlignment="Left" Margin="54,36,0,0" Name="cmbProvince" ItemsSource="{Binding}" DisplayMemberPath="Name" VerticalAlignment="Top" Width="120" />

         <TextBlock Height="23" HorizontalAlignment="Left" Margin="207,36,0,0" Name="textBlock2" Text="市" VerticalAlignment="Top" />

         <ComboBox Height="23" HorizontalAlignment="Left" Margin="242,36,0,0" Name="cmbCity" ItemsSource="{Binding SelectedItem.Citys, ElementName=cmbProvince}"  DisplayMemberPath="Name" VerticalAlignment="Top" Width="120" />

     </Grid>

 </Window>

 using System;

 using System.Collections.Generic;

 using System.Linq;

 using System.Text;

 using System.Windows;

 using System.Windows.Controls;

 using System.Windows.Data;

 using System.Windows.Documents;

 using System.Windows.Input;

 using System.Windows.Media;

 using System.Windows.Media.Imaging;

 using System.Windows.Navigation;

 using System.Windows.Shapes;

 namespace Demo

 {

     /// <summary>

     /// MainWindow.xaml 的交互逻辑

     /// </summary>

     public partial class MainWindow : Window

     {

         public List<Province> ProvinceList { set; get; }

         public MainWindow()

         {

             InitializeComponent();

             LoadData();

             this.cmbProvince.DataContext = ProvinceList;

         }

         /// <summary>

         /// 构建数据

         /// </summary>

         public void LoadData()

         {

             ProvinceList = new List<Province>();

             Province bj = new Province();

             bj.Name = "北京";

             bj.Citys = new List<City>();

             City city1 = new City() { Name = "海淀" };

             bj.Citys.Add(city1);

             city1 = new City() { Name = "朝阳" };

             bj.Citys.Add(city1);

             city1 = new City() { Name = "西城" };

             bj.Citys.Add(city1);

             Province sh = new Province() { Name = "上海" };

             sh.Citys = new List<City>();

             city1 = new City() { Name = "静安" };

             sh.Citys.Add(city1);

             city1 = new City() { Name = "徐汇" };

             sh.Citys.Add(city1);

             city1 = new City() { Name = "金山" };

             sh.Citys.Add(city1);

             ProvinceList.Add(bj);

             ProvinceList.Add(sh);

         }

     }

 }

 namespace Demo

 {

     public class City

     {

         public string Name { get; set; }

     }

 }

 using System.Collections.Generic;

 namespace Demo

 {

     public class Province

     {

         public string Name { get; set; }

         public List<City> Citys { get; set; }

     }

 }