CollectionView in WPF

wpf的集合controls, 都会有一个内在的viewmodel, 即ICollectionView;来支持sort ,filter, collection view 就是view model

wpf 根据data source 集合自动产生对应的collection view, ListCollectionView(IList ,OberservableCollection),BindingListCollectionView;(BindingListCollectionView 没有像ListCollectionView一样的sort能力，它使用IBindingList的sort定义，具体见：http://www.wpfmentor.com/2008/12/how-to-sort-bindinglist-using.html)

对于IEnumerable数据源，产生一个EnumerableCollectionView,可惜这个类是internal .如果ListBox.ItemSource = Ilist, 自动产生一个ListCollectionView.

用ICollectionView CollectionViewSource.GetDefaultView(object) 可以获得collection view,并且通过这个类在xaml中操作collection view.

在ListCollectionView中，有一个internal list，当用户设置sort,filter时通过这个list产生需要的enumerable在界面上展示；而不用真正修改数据源。(SourceCollection).

对于实现了INotifyPropertyChanged，INotifyCollectionChanged的数据源，如果设置IsSynchronizationCurrentItem=true; 这样就能实现view与collection view 的完全同步，通过操作collection view，也能在view中显示出来。如CurrentItem,CurrentPosition,都是界面对应的item与position. 比如设置了filter,在原数据源中此数据index=3,在 view中显示index=2,则currentPosition =2.

附custom observable collection 实现：

public class MySampleClass : INotifyPropertyChanged

{

public int MyProperty

{

get

{

return _myProperty;

}

set

{

if (_myProperty == value)

return;

_myProperty = value;

OnPropertyChanged("MyProperty");

}

public interface ICustomObservableCollection<T> : ICollection<T>, INotifyCollectionChanged, INotifyPropertyChanged

{

}

#region Implementation of INotifyPropertyChanged  
public event PropertyChangedEventHandler PropertyChanged; 
  
protected virtual void OnPropertyChanged(PropertyChangedEventArgs e) 
{ 
    if (PropertyChanged != null) 
    { 
       PropertyChanged(this, e); 
    } 
} 
  
private void OnPropertyChanged(string propertyName) 
{ 
    OnPropertyChanged(new PropertyChangedEventArgs(propertyName)); } 
  
#endregion
 
 
#region Implementation of INotifyCollectionChanged   
public event NotifyCollectionChangedEventHandler CollectionChanged; 
  
protected virtual void OnCollectionChanged(NotifyCollectionChangedEventArgs e) 
{ 
   if (CollectionChanged != null) 
   { 
       using (BlockReentrancy()) 
      { 
            CollectionChanged(this, e); 
        } 
  } 
} 
 
private void OnCollectionChanged(NotifyCollectionChangedAction action, object item) 
 
   OnCollectionChanged(new NotifyCollectionChangedEventArgs(action, item)); 
} 
  
private void OnCollectionChanged(NotifyCollectionChangedAction action, object item, int index) 
{ 
    OnCollectionChanged(new NotifyCollectionChangedEventArgs(action, item, index)); 
} 
  
private void OnCollectionReset() 
    OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset)); 
} 
  
.#endregion
 