Reputation: 2999
I wanted to bind to an ObservableCollection
in XAML and also apply the grouping there. In principle, this worked fine.
<UserControl.Resources>
<CollectionViewSource x:Key="cvs" Source="{Binding Path=TestTemplates}">
<CollectionViewSource.SortDescriptions>
<scm:SortDescription PropertyName="Title"/>
</CollectionViewSource.SortDescriptions>
<CollectionViewSource.GroupDescriptions>
<PropertyGroupDescription PropertyName="TestCategory"/>
</CollectionViewSource.GroupDescriptions>
</CollectionViewSource>
</UserControl.Resources>
Then the data binding expression became ItemsSource="{Binding Source={StaticResource ResourceKey=cvs}}"
instead of ItemsSource="{Binding Path=TestTemplates}"
.
At first, everything seemed cool, until I wanted to refresh the UI from the view model. The problem is, that CollectionViewSource.GetDefaultView(TestTemplates)
returned a different view than the one from XAML where the grouping was applied. Thus, I could not set selection or do anything useful with it.
I could fix it by binding the list again directly to the view model's property and setting up the grouping in the code-behind. But I'm not that happy with this solution.
private void UserControlLoaded(object sender, RoutedEventArgs e)
{
IEnumerable source = TemplateList.ItemsSource;
var cvs = (CollectionView)CollectionViewSource.GetDefaultView(source);
if (cvs != null)
{
cvs.SortDescriptions.Add(new SortDescription("Title", ListSortDirection.Ascending));
cvs.GroupDescriptions.Add(new PropertyGroupDescription("TestCategory"));
}
}
I assume, the reason for that is already given by John Skeet here.
Nevertheless, I would expect that there should be a way to get the right view. Am I wrong?
Upvotes: 9
Views: 6240
Reputation: 2999
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?
Upvotes: 2
Reputation: 3361
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.
Upvotes: 6
Reputation: 178820
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.
Upvotes: 6