Catching CollectiveViewSource's Filter event in ViewModel

How do I 开发者_运维百科catch Filter event of CollectionViewSource in ViewModel using MVVM light?

Not familiar with MVVM Light however I am pretty sure what you are talking about is standard WPF framework bits.

The Filter property on your ICollectionView is a Predicate<object> which you can set to a given method on your ViewModel which will be called each time the Filter needs exercised.

One way to achieve this is by defining your ICollectionView as a property within the ViewModel which is being bound to within your View.

private ICollectionView _view;

public ICollectionView Data
{
    get 
    {
        if (_view == null)
        {
            _view = CollectionViewSource.GetDefaultView(someCollection);
            _view.Filter = Filter;
        }

        return _view;
    }
}

private bool Filter(object arg)
{
     //arg is the object being filtered on to make the decision of
     //it being included in the returned ICollectionView

     return true;
}

This allows all logic to remain in the ViewModel which I believe is your ultimate goal.

You might be interested in the BookLibrary sample application which delegates the Filter of a CollectionViewSource to the ViewModel. However, it doesn't use MVVM Light. The sample is part of the WPF Application Framework (WAF).