public class EditComboBox : ComboBox
  {
    private bool t = true;//首次獲取焦點標志位
    private ObservableCollection<object> bindingList = new ObservableCollection<object>();//數據源綁定List
    private string editText = "";//編輯文本內容

    /// <summary>
    /// 注冊依賴事件
    /// </summary>
    public static readonly DependencyProperty ItemsSourcePropertyNew = DependencyProperty.Register("MyItemsSource", typeof(IEnumerable), typeof(EditComboBox), new FrameworkPropertyMetadata(new PropertyChangedCallback(ValueChanged)));
    /// <summary>
    /// 數據源改變，添加數據源到綁定數據源
    /// </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();
      //遍歷循環(huán)操作
      foreach (var item in ecb.MyItemsSource)
      {
        ecb.bindingList.Add(item);
      }
    }
    /// <summary>
    /// 設置或獲取ComboBox的數據源
    /// </summary>
    public IEnumerable MyItemsSource
    {
      get
      {
        return (IEnumerable)GetValue(ItemsSourcePropertyNew);
      }

      set
      {
        if (value == null)
          ClearValue(ItemsSourcePropertyNew);
        else
          SetValue(ItemsSourcePropertyNew, value);
      }
    }
    /// <summary>
    /// 重寫初始化
    /// </summary>
    /// <param name="e"></param>
    protected override void OnInitialized(EventArgs e)
    {
      base.OnInitialized(e);
      this.IsEditable = true;
      this.IsTextSearchEnabled = false;
      this.ItemsSource = bindingList;
    }
    /// <summary>
    /// 下拉框獲取焦點，首次搜索文本編輯框
    /// </summary>
    /// <param name="e"></param>
    protected override void OnGotFocus(RoutedEventArgs e)
    {
      if (t)
        FindTextBox(this);
      else
        t = false;
    }
    /// <summary>
    /// 搜索編輯文本框，添加文本改變事件
    /// </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)
        {
          //注冊文本改變事件
          (child as TextBox).TextChanged += EditComboBox_TextChanged;
        }
        else
        {
          FindTextBox(child);
        }
      }
    }
    /// <summary>
    /// 文本改變，動態(tài)控制下拉條數據源
    /// </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>
    /// 組合框關閉，數據源恢復
    /// </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>
    /// 過濾符合條件的數據項，添加到數據源項中
    /// </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());
      }
    }
  }