C#实现带搜索功能的ComboBox

public class EditComboBox : ComboBox
  {
    private bool t = true;//首次获取焦点标志位
    private ObservableCollection<object> bindingList = new ObservableCollection<object>();//数据源绑定List
    private string editText = "";//编辑文本内容

    /// <summary>
    /// 注册依赖事件
    /// </summary>
    public static readonly DependencyProperty ItemsSourcePropertyNew = DependencyProperty.Register("MyItemsSource",typeof(IEnumerable),typeof(EditComboBox),new FrameworkPropertyMetadata(new PropertyChangedCallback(ValueChanged)));
    /// <summary>
    /// 数据源改变，添加数据源到绑定数据源
    /// </summary>
    /// <param name="d"></param>
    /// <param name="e"></param>
    private static void ValueChanged(DependencyObject d,DependencyPropertyChangedEventArgs e)
    {
      EditComboBox ecb = d as EditComboBox;
      ecb.bindingList.Clear();
      //遍历循环操作
      foreach (var item in ecb.MyItemsSource)
      {
        ecb.bindingList.Add(item);
      }
    }
    /// <summary>
    /// 设置或获取ComboBox的数据源
    /// </summary>
    public IEnumerable MyItemsSource
    {
      get
      {
        return (IEnumerable)GetValue(ItemsSourcePropertyNew);
      }

      set
      {
        if (value == null)
          ClearValue(ItemsSourcePropertyNew);
        else
          SetValue(ItemsSourcePropertyNew,value);
      }
    }
    /// <summary>
    /// 重写初始化
    /// </summary>
    /// <param name="e"></param>
    protected override void OnInitialized(EventArgs e)
    {
      base.OnInitialized(e);
      this.IsEditable = true;
      this.IsTextSearchEnabled = false;
      this.ItemsSource = bindingList;
    }
    /// <summary>
    /// 下拉框获取焦点，首次搜索文本编辑框
    /// </summary>
    /// <param name="e"></param>
    protected override void OnGotFocus(RoutedEventArgs e)
    {
      if (t)
        FindTextBox(this);
      else
        t = false;
    }
    /// <summary>
    /// 搜索编辑文本框，添加文本改变事件
    /// </summary>
    /// <param name="obj"></param>
    private void FindTextBox(DependencyObject obj)
    {
      for (int i = 0; i < VisualTreeHelper.GetChildrenCount(obj); i++)
      {
        DependencyObject child = VisualTreeHelper.GetChild(obj,i);
        if (child!=null && child is TextBox)
        {
          //注册文本改变事件
          (child as TextBox).TextChanged += EditComboBox_TextChanged;
        }
        else
        {
          FindTextBox(child);
        }
      }
    }
    /// <summary>
    /// 文本改变，动态控制下拉条数据源
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    private void EditComboBox_TextChanged(object sender,TextChangedEventArgs e)
    {
      TextBox tb = sender as TextBox;
      if(tb.IsFocused)
      {
        this.IsDropDownOpen = true;
        if (editText == this.Text)
          return;
        editText = this.Text;
        SetList(editText);
      }
    }
    /// <summary>
    /// 组合框关闭，数据源恢复
    /// </summary>
    /// <param name="e"></param>
    protected override void OnDropDownClosed(EventArgs e)
    {
      base.OnDropDownClosed(e);
      if (MyItemsSource == null)
        return;
      foreach (var item in MyItemsSource)
      {
        if (!bindingList.Contains(item))
          bindingList.Add(item);
      }
    }
    /// <summary>
    /// 过滤符合条件的数据项，添加到数据源项中
    /// </summary>
    /// <param name="txt"></param>
    private void SetList(string txt)
    {
      try
      {
        string temp1 = "";
        string temp2 = "";
        if (MyItemsSource == null)
          return;
        foreach (var item in MyItemsSource)
        {
          temp1 = item.GetType().GetProperty(this.DisplayMemberPath).GetValue(item,null).ToString();
          if (string.IsNullOrEmpty(this.SelectedValuePath))
          {
            temp2 = "";
          }
          else
          {
            temp2 = item.GetType().GetProperty(this.SelectedValuePath).GetValue(item,null).ToString();
          }
          if(temp1.Contains(txt)||temp2.StartsWith(txt))
          {
            if (!bindingList.Contains(item))
              bindingList.Add(item);
          }
          else if (bindingList.Contains(item))
          {
            bindingList.Remove(item);
          }
        }
      }
      catch (Exception ex)
      {
        MessageBox.Show(ex.ToString());
      }
    }
  }