在WPF中，CollectionViewSource是一个经常用到的集合类型，主要用于对后台数据排序，条件筛选或分组操作。

     场景：当需要筛选包含“test”的数据项时，我们会分步输入搜索条件，依次为“t”、“te”、“tes”,而最后是“test”,而我们简单的处理经常会是在Textbox的TextChanged事件中直接添加CollectionViewSource的View的Refresh，这样筛选操作实际上进行了四次筛选操作，每一步筛选操作都会Filter及RefreshUI，对于应用来说，前几次的Filter及RefreshUI均是无用的，白白浪费了资源。

     解决方案：

     1：TextChanged中的Refresh操作进行延迟刷新，即用户输入完成后先不进行刷新，超过一定的时间再进行刷新，对于筛选条件，需要一个定时器延迟，（当筛选条件过多时，定时器数量过量，不易管理，易出错）

     2：将延迟做到CollectionViewSource中View的刷新供码中，比如，封装一个方法SourceRefresh，协定刷新_source时只能通过SourceRefresh方法。

private CollectionViewSource _source = new CollectionViewSource();        private DispatcherTimer timer=new DispatcherTimer();        public void SourceRefresh()        {            if(timer.IsEnabled)                timer.Stop();            timer.Interval = new TimeSpan(0, 0, 0, 0, 200);            timer.Tick += (sender, e) =>            {                timer.Stop();                if (null != _source.View)                    _source.View.Refresh();            };            timer.Start();        }

　　看源码会比较直观点，如下：

　　

　　下面的代码是我写的例子，可以参考下：

　　

public class MyListCollectionView
      
        : ListCollectionView    {        public MyListCollectionView(IList list) : base(list)        {            _filterTimer.Interval = new TimeSpan(0, 0, 0, 0, 1);            _filterTimer.Tick += (sender, e) =>            {                CancelAllTimer();                RefreshFilter();                _freshUITimer.Start();                Console.WriteLine("A");            };            _freshUITimer.Interval = new TimeSpan(0, 0, 0, 0, 500);            _freshUITimer.Tick += (sender, e) =>            {                CancelAllTimer();                RefreshUI();                _freshCurrentTimer.Start();                Console.WriteLine("B");            };            _freshCurrentTimer.Interval = new TimeSpan(0, 0, 0, 0, 20);            _freshCurrentTimer.Tick += (sender, e) =>            {                CancelAllTimer();                RefreshCurrent();                Console.WriteLine("C");            };        }        private DispatcherTimer _filterTimer = new DispatcherTimer();        private DispatcherTimer _freshUITimer = new DispatcherTimer();        private DispatcherTimer _freshCurrentTimer = new DispatcherTimer();        private bool _isFreshFilter = false;        private void CancelAllTimer()        {            _filterTimer.Stop();            _freshUITimer.Stop();            _freshCurrentTimer.Stop();        }        protected override void RefreshOverride()        {            _filterTimer.Start();        }        protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs args)        {            if (!_isFreshFilter)                base.OnCollectionChanged(args);        }        protected override void OnCurrentChanged()        {            if (!_isFreshFilter)                base.OnCurrentChanged();        }        protected override void OnPropertyChanged(PropertyChangedEventArgs e)        {            if (!_isFreshFilter)                base.OnPropertyChanged(e);        }        private void RefreshFilter()        {            try            {                //cancel all                _isFreshFilter = true;                base.RefreshOverride();            }            finally            {                _isFreshFilter = false;            }        }        private void RefreshUI()        {            OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));        }        private void RefreshCurrent()        {            OnCurrentChanged();            OnPropertyChanged("IsCurrentAfterLast");            OnPropertyChanged("IsCurrentBeforeFirst");            OnPropertyChanged("CurrentPosition");            OnPropertyChanged("CurrentItem");        }        private void OnPropertyChanged(string proName)        {            OnPropertyChanged(new PropertyChangedEventArgs(proName));        }    }  public class MyCollection
       
         : ObservableCollection
        
         , ICollectionViewFactory    {        public MyCollection()        {        }        public MyCollection(IList
         
           list) : base(list)        {        }        public MyCollection(IEnumerable
          
            list) : base(list)        {        }        public MyListCollectionView
           
             _view; public ICollectionView CreateView() { _view = new MyListCollectionView
            
             (this); return _view; } }