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