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
 

posted on 2009-07-01 12:43  oyl  阅读(808)  评论(0)  编辑  收藏  举报

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