How can I get the CollectionView that is defined in XAML

You could not just do that?

var _viewSource = this.FindResource("cvs") as CollectionViewSource;

If the data is connected, I assume that will have an updated view.

I tend to just expose the collection view from the VM rather than have the view define it:

public ICollection<Employee> Employees{    get { ... }}public ICollectionView EmployeesView{    get { ... }}

That way your VM has full control over what is exposed to the view. It can, for example, change the sort order in response to some user action.

Found a way, based on J. Lennon's answer. If I pass something that has access to the resources with my command, then I can look up the CollectionViewSource there.

In XAML (CollectionViewResource as above):

<Button Command="{Binding Command}" CommandParameter="{Binding RelativeSource={RelativeSource Self}}">Do it!</Button>

And in the VM code:

private void Execute(object parm){    var fe = (FrameworkElement)parm;    var cvs = (CollectionViewSource)fe.FindResource("cvs");    cvs.View.Refresh();}

The Execute is the one that is given to the RelayCommand.

This would answer the question, but I don't like it very much. Opinions?