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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
   
     names = new ObservableCollection
    
     ();        private bool popupIsOpen = false;        public bool PopupIsOpen        {            get             {                 return popupIsOpen;            }            set             {                 popupIsOpen = value;                this.PropertyChanged(this, new PropertyChangedEventArgs("PopupIsOpen"));            }        }        public ObservableCollection
     
       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：

/// 
    /// MainWindow.xaml 的交互逻辑    /// 
    public partial class MainWindow : Window    {        private MainWindowModel model = new MainWindowModel();        private List
   
     threadPool = new List
    
     ();        public MainWindow()        {            InitializeComponent();            this.DataContext = model;        }        /// 
     
        /// 在此增加内容        /// 
        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);                    }                }));        }        /// 
     
        /// 下拉菜单消失要清空内容        /// 
        /// 
             /// 
             private void popupContent_Closed(object sender, EventArgs e)        {            this.model.Names.Clear();        }        /// 
     
        /// 文本框失去焦点，下拉列表隐藏        /// 
        /// 
             /// 
             private void textBox1_LostFocus(object sender, RoutedEventArgs e)        {            this.model.PopupIsOpen = false;        }        /// 
     
        /// 文字内容改变，下拉类表出现        /// 
        /// 
             /// 
             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
     
      ;                if (this.model.Names.Count <= 0)                {                    this.model.PopupIsOpen = false;                }            };            threadPool.Add(worker);            Thread.Sleep(100);            if (threadPool.Count > 0)            {                threadPool[0].RunWorkerAsync();            }        }        /// 
      
        /// 子项被选中，下拉列表消失        /// 
        /// 
              /// 
              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：

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。

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