CODEWITHSUNDEEP
c#wpfxamlmvvm
Ravi Dugar
Ravi Dugar

Reputation: 7

The alternate style for ListBox in WPF not working as expected if the collection has some items which needs to be hidden

I am trying to bind my collection to a listbox. The collection contains some items which are to be hidden and are to be shown based on certain conditions.But when I do this the alternate styles are not applied properly.

For example: Case 1 : where all items are visible, I get the output like this: Item1(grey) Item2(white) Item3(grey) Item4(white) Item5(grey) Item6(white) Item7(grey)

Case2: where Item2 is hidden, I get the output as: Item1(grey) Item3(grey) Item4(white) Item5(grey) Item6(white) Item7(grey)

How do I resolve this without rebinding the collection?

Upvotes: 0

Views: 158

Answers (1)

Gusdor
Gusdor

Reputation: 14332

Rather than hide the items (presumably in the ListBoxItem control template, or the ListBox ItemTemplate), you should use a CollectionViewSource to filter them out.

This is because the items are still technically there - you cannot see them but the listbox can.

See this link for details on filtering. http://wpftutorial.net/DataViews.html

To filter a collection view you can define a callback method that determines if the item should be part of the view or not. That method should have the following signature: bool Filter(object item). Now set the delegate of that method to the Filter property of the CollectionView and you're done.

ICollectionView _customerView = CollectionViewSource.GetDefaultView(customers);
_customerView.Filter = CustomerFilter

private bool CustomerFilter(object item)
{
    Customer customer = item as Customer;
    return customer.Name.Contains( _filterString );
}

Upvotes: 0

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