的ObservableCollection没有注意到，当它改变项（即使有INotifyPropertyChanged的）

问题描述

没有人知道为什么会这样code不工作：

does anyone know why this code doesn't work:

public class CollectionViewModel : ViewModelBase {
    public ObservableCollection<EntityViewModel> ContentList
    {
        get { return _contentList; }
        set
        {
            _contentList = value;
            RaisePropertyChanged("ContentList");
            //I want to be notified here when something changes..?
            //debugger doesn't stop here when IsRowChecked is toggled
        }
     }
}

public class EntityViewModel : ViewModelBase
{

    private bool _isRowChecked;

    public bool IsRowChecked
    {
        get { return _isRowChecked; }
        set { _isRowChecked = value; RaisePropertyChanged("IsRowChecked"); }
    }
}

PS：ViewModelBase containts家居RaisePropertyChanged等，它的工作一切，除了这个问题..

PS: ViewModelBase containts everything for RaisePropertyChanged etc. and it's working for everything else except this problem..

推荐答案

当您更改集合中的一个值。ContentList的设置方法不会被调用，而不是你应该寻找出的的事件触发。

The ContentList's Set method will not get called when you change a value inside the collection, instead you should be looking out for the CollectionChanged event firing.

public class CollectionViewModel : ViewModelBase
{
    public ObservableCollection<EntityViewModel> ContentList
    {
        get { return _contentList; }
    }

    public CollectionViewModel()
    {
         _contentList = new ObservableCollection<EntityViewModel>();
         _contentList.CollectionChanged += ContentCollectionChanged;
    }

    public void ContentCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        //This will get called when the collection is changed
    }
}

---

修改

好吧，今天我已经咬伤MSDN文档犯错的两倍。在链接我给你这样说的：

Okay, that's twice today I've been bitten by the MSDN documentation being wrong. In the link I gave you it says:

时发生一个项目中添加，删除，
  改变，移动，或整个列表
  刷新。

但它实际上的当一个项目改变不的火灾。我猜你需要再一个更暴力破解的方法：

But it actually doesn't fire when an item is changed. I guess you'll need a more bruteforce method then:

public class CollectionViewModel : ViewModelBase
{
    public ObservableCollection<EntityViewModel> ContentList
    {
        get { return _contentList; }
    }

    public CollectionViewModel()
    {
         _contentList = new ObservableCollection<EntityViewModel>();
         _contentList.CollectionChanged += ContentCollectionChanged;
    }

    public void ContentCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        if (e.Action == NotifyCollectionChangedAction.Remove)
        {
            foreach(EntityViewModel item in e.OldItems)
            {
                //Removed items
                item.PropertyChanged -= EntityViewModelPropertyChanged;
            }
        }
        else if (e.Action == NotifyCollectionChangedAction.Add)
        {
            foreach(EntityViewModel item in e.NewItems)
            {
                //Added items
                item.PropertyChanged += EntityViewModelPropertyChanged;
            }
        }
    }

    public void EntityViewModelPropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        //This will get called when the property of an object inside the collection changes
    }
}

如果您将需要这一点，你可能要继承了很多自己的的ObservableCollection 触发 Col​​lectionChanged 事件当一个成员会自动触发其的PropertyChanged 事件（像它说，它应该在文档中......）

If you are going to need this a lot you may want to subclass your own ObservableCollection that triggers the CollectionChanged event when a member triggers its PropertyChanged event automatically (like it says it should in the documentation...)

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