WPF：下拉列表的简单实现
最近在一个WPF项目中用到一个下拉列表，随着用户输入字符而进行显示，使用了绑定等知识，虽然实现比较简单，可是在性能上也是想了很多办法终于才勉强可以用，与大家分享下。
用于页面绑定的模型类：
public class MainWindowModel : INotifyPropertyChanged { public event PropertyChangedEventHandler PropertyChanged; private ObservableCollection<Content> names = new ObservableCollection<Content>(); private bool popupIsOpen = false; public bool PopupIsOpen { get { return popupIsOpen; } set { popupIsOpen = value; this.PropertyChanged(this, new PropertyChangedEventArgs("PopupIsOpen")); } } public ObservableCollection<Content> Names { get { return this.names; } set { this.names = value; this.PropertyChanged(this, new PropertyChangedEventArgs("Names")); } } } public class Content { private string name=string.Empty; public string Name { get { return this.name; } set { name = value; } } }后台代码：
/// <summary> /// MainWindow.xaml 的交互逻辑 /// </summary> public partial class MainWindow : Window { private MainWindowModel model = new MainWindowModel(); private List<BackgroundWorker> threadPool = new List<BackgroundWorker>(); public MainWindow() { InitializeComponent(); this.DataContext = model; } /// <summary> /// 在此增加内容 /// </summary> private void InitialSetValue() { this.Dispatcher.BeginInvoke(new Action(() => { this.model.Names.Clear(); for (int i = 0; i < 100; i++) { Content content = new Content(); content.Name = i.ToString() + i.ToString() + i.ToString() + i.ToString() + i.ToString(); this.model.Names.Add(content); } })); } /// <summary> /// 下拉菜单消失要清空内容 /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private void popupContent_Closed(object sender, EventArgs e) { this.model.Names.Clear(); } /// <summary> /// 文本框失去焦点，下拉列表隐藏 /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private void textBox1_LostFocus(object sender, RoutedEventArgs e) { this.model.PopupIsOpen = false; } /// <summary> /// 文字内容改变，下拉类表出现 /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private void textBox1_TextChanged(object sender, TextChangedEventArgs e) { this.model.PopupIsOpen = true; if (threadPool.Count > 0) { threadPool[0].CancelAsync(); } threadPool.Clear(); string key = this.textBox1.Text.Trim(); if (string.IsNullOrEmpty(key)) { this.model.PopupIsOpen = false; return; } BackgroundWorker worker = new BackgroundWorker(); worker.WorkerReportsProgress = true; worker.WorkerSupportsCancellation = true; worker.DoWork += (o, p) => { InitialSetValue(); p.Result = this.model.Names; }; worker.RunWorkerCompleted += (o, p) => { this.model.Names = p.Result as ObservableCollection<Content>; if (this.model.Names.Count <= 0) { this.model.PopupIsOpen = false; } }; threadPool.Add(worker); Thread.Sleep(100); if (threadPool.Count > 0) { threadPool[0].RunWorkerAsync(); } } /// <summary> /// 子项被选中，下拉列表消失 /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private void item_SelectionChanged(object sender, SelectionChangedEventArgs e) { var data = (sender as ListBox).SelectedItem as Content; if (data == null) { this.model.PopupIsOpen = false; return; } try { this.textBox1.TextChanged -= new TextChangedEventHandler(textBox1_TextChanged); var searchtext = data.Name; this.model.PopupIsOpen = false; } catch { } finally { this.textBox1.TextChanged += new TextChangedEventHandler(textBox1_TextChanged); } } }页面代码：
<Window x:Class="TestPopup.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"> <Grid> <TextBox Height="38" HorizontalAlignment="Left" Margin="71,89,0,0" LostFocus="textBox1_LostFocus" TextChanged="textBox1_TextChanged" Name="textBox1" VerticalAlignment="Top" Width="236" /> <Popup Name="popupContent" StaysOpen="False" IsOpen="{Binding PopupIsOpen}" Closed="popupContent_Closed" Placement="Bottom" PlacementTarget="{Binding ElementName=textBox1}" > <ListBox Name="contentItems" SelectionChanged="item_SelectionChanged" ItemsSource="{Binding Names}" MinWidth="{Binding ElementName=textBox1, Path=ActualWidth}"> <ListBox.ItemTemplate> <DataTemplate> <TextBlock Margin="5,5" FontSize="15" Text="{Binding Name}" Foreground="Gray"/> </DataTemplate> </ListBox.ItemTemplate> </ListBox> </Popup> </Grid></Window>效果：
主要注意的有一点，下拉列表消失时一定要清除数据，不然下次显示的时候会很慢。在用的时候找了好久才发现这个问题。
详细工程：http://download.csdn.net/detail/yysyangyangyangshan/4762184