WPF中DataGrid控件的过滤（Filter）性能分析及优化
1）DataGrid的过滤过程：
用户输入过滤条件
调用DataGrid的CollectionViewSource的View.Refresh()功能
DataGrid控件内部调用CollectionView的RefreshOverride方法
CollectionView会调用CollectionViewSource的Filter回调函数来过滤符合自定义过滤条件的数据
CollectionView调用内部的OnCollectionChanged和OnCurrentChanged分别更新界面上的数据和当前选中的Item
2）通过分析发现（10W条数据， 实时过滤时UI非常卡，导致用户输入过滤字符丢失），调用CollectionViewSource的View.Refresh()的性能损耗主要集中于：
CollectionViewSource.Filter注册的方法，以及OnCollectionChanged（每次更新都导致ItemContainerGenerator重新构造UI元素）
3）优化方向：
减少CollectionViewSource.Filter注册的方法的耗时（在实时过滤中每个条件的更改都会调用Refresh从而调用Filter方法）
减少OnCollectionChanged调用的次数。
4）具体优化措施：
实例化3个Timer， 分别用于获取过滤后的数组（调用Filter)、调用OnCollectionChanged、OnCurrentItemChanged。3个timer分别由前一个timer完成时启动， 形成一个顺序操作。每次调用Timer时，先停止后续Timer的执行， 这样保证在合理的时间间隔里只有一次Refresh完整完成。
5）实现：
下面代码重载了ObservableCollection， 然后创建自定义的ListCollectionview.使用时只要用CustomCollection声明列表数据，包装为CollectionViewSource， 绑定到DataGrid的ItemSource即可。
//声明数组数据
public CustomCollection<StudyInfoModel> StudyList
{
get { return studyList; }
}
//包装为CollectionView
<CollectionViewSource Source="{Binding StudyList}" x:Key="StudyListView">
<CollectionViewSource.SortDescriptions>
<ComponentModel:SortDescription PropertyName="DateTime" Direction="Descending"/>
</CollectionViewSource.SortDescriptions>
</CollectionViewSource>
//绑定到DataGrid
<DataGrid ItemsSource="{Binding Mode=OneWay, Source={StaticResource StudyListView}}" />
public class CustomCollectionView<T> : ListCollectionView
{
private readonly DispatcherTimer _timerRefreshCalculate = new DispatcherTimer();
private readonly DispatcherTimer _timerRefreshUI = new DispatcherTimer();
private readonly DispatcherTimer _timerRefreshCurrentItem = new DispatcherTimer();
private bool _isRefreshingCalculate = false;
private object _oldSelectedItem = null;
public CustomCollectionView(IList list)
: base(list)
{
_timerRefreshUI.Interval = new TimeSpan(0, 0, 0, 0, 300);
_timerRefreshCurrentItem.Interval = new TimeSpan(0, 0, 0, 0, 500);
_timerRefreshCalculate.Interval = new TimeSpan(0, 0, 0, 0, 200);
}
#region Override Method
protected override void OnPropertyChanged(PropertyChangedEventArgs e)
{
if (_isRefreshingCalculate)
{
return;
}
base.OnPropertyChanged(e);
}
protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs args)
{
if (_isRefreshingCalculate)
{
return;
}
base.OnCollectionChanged(args);
}
protected override void OnCurrentChanged()
{
if (_isRefreshingCalculate)
{
return;
}
base.OnCurrentChanged();
}
protected override void RefreshOverride()
{
CancelAllRefreshRequest();
StartRefresh();
}
#endregion
#region Public Method
public void CancelAllRefreshRequest()
{
_timerRefreshCurrentItem.Stop();
_timerRefreshCurrentItem.Tick -= TimerCurrentItem;
_timerRefreshUI.Stop();
_timerRefreshUI.Tick -= TimerUI;
_timerRefreshCalculate.Stop();
_timerRefreshCalculate.Tick -= TimerCalculate;
if (null != this.CurrentItem)
{
_oldSelectedItem = this.CurrentItem;
}
SetCurrent(null, -1);
}
#endregion
#region Private Method
private void StartRefresh()
{
_timerRefreshCurrentItem.Stop();
_timerRefreshCurrentItem.Tick -= TimerCurrentItem;
_timerRefreshUI.Stop();
_timerRefreshUI.Tick -= TimerUI;
_timerRefreshCalculate.Stop();
_timerRefreshCalculate.Tick -= TimerCalculate;
//begin to refresh from calculate, so set flag by true.
//and it shielded any collection action during the calculating time.
//this logic will avoid items are not correct at UI during refresh.
_isRefreshingCalculate = true;
_timerRefreshCalculate.Tick += TimerCalculate;
_timerRefreshCalculate.Start();
}
private void RefreshCalculate(CancellationToken? token)
{
_timerRefreshCalculate.Tick -= TimerCalculate;
if (null != token && null != token.Value)
{
token.Value.ThrowIfCancellationRequested();
}
_isRefreshingCalculate = true;
base.RefreshOverride();
_isRefreshingCalculate = false;
if (null != token && null != token.Value)
{
token.Value.ThrowIfCancellationRequested();
}
}
private void RefreshUI()
{
try
{
//detach timer
_timerRefreshUI.Tick -= TimerUI;
base.OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
//set timer to refresh current item
_timerRefreshCurrentItem.Tick -= TimerCurrentItem;
_timerRefreshCurrentItem.Tick += TimerCurrentItem;
_timerRefreshCurrentItem.Start();
}
catch (OperationCanceledException)
{
return;
}
}
private void RefreshCurrentItem()
{
_timerRefreshCurrentItem.Tick -= TimerCurrentItem;
if (null == this.InternalList || this.InternalList.Count <= 0)
{
return;
}
if (null != _oldSelectedItem)
{
var index = this.InternalList.IndexOf(_oldSelectedItem);
if (index != -1)
{
SetCurrent(_oldSelectedItem, index);
}
else
{
SetCurrent(this.InternalList[0], 0);
}
}
else
{
SetCurrent(this.InternalList[0], 0);
}
//Set event to update UI
base.OnCurrentChanged();
this.OnPropertyChanged("IsCurrentAfterLast");
this.OnPropertyChanged("IsCurrentBeforeFirst");
this.OnPropertyChanged("CurrentPosition");
this.OnPropertyChanged("CurrentItem");
}
private void TimerCalculate(object sender, EventArgs e)
{
_timerRefreshCurrentItem.Stop();
_timerRefreshCurrentItem.Tick -= TimerCurrentItem;
_timerRefreshUI.Stop();
_timerRefreshUI.Tick -= TimerUI;
try
{
RefreshCalculate(null);
}
catch (OperationCanceledException)
{
}
_timerRefreshUI.Interval = new TimeSpan(0, 0, 0, 0, 50 + Math.Min((int)(this.InternalCount / 80), 300));
_timerRefreshUI.Tick += TimerUI;
_timerRefreshUI.Start();
}
private void TimerUI(object sender, EventArgs e)
{
RefreshUI();
}
private void TimerCurrentItem(object sender, EventArgs e)
{
RefreshCurrentItem();
}
private void OnPropertyChanged(string propertyName)
{
OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
}
#endregion
}
public class CustomCollection<T> : ObservableCollection<T>, ICollectionViewFactory
{
public CustomCollection()
{
}
public CustomCollection(List<T> list)
: base(list)
{
}
public CustomCollection(IEnumerable<T> collection)
: base(collection)
{
}
public ICollectionView CreateView()
{
return new CustomCollectionView<T>(this);
}
}
https://muzizongheng.blog.csdn.net/
