I have a hypothetical tree view that contains this data:
RootNode
Leaf
vein
SecondRoot
seeds
flowers
I am trying to filter the nodes in order to show only the nodes that contain a certain text. Say if I specify "L", the tree will be filtered and show only RootNode->Leaf and SecondRoot->flowers (because they both contain the letter L).
Following the m-v-vm pattern, I have a basic TreeViewViewModel class like this:
public class ToolboxViewModel
{
...
readonly ObservableCollection<TreeViewItemViewModel> _treeViewItems = new ObservableCollection<TreeViewItemViewModel>();
public ObservableCollection<TreeViewItemViewModel> Headers
{
get { return _treeViewItems; }
}
private string _filterText;
public string FilterText
{
get { return _filterText; }
set
{
if (value == _filterText)
return;
_filterText = value;
ICollectionView view = CollectionViewSource.GetDefaultView(Headers);
view.Filter = obj => ((TreeViewItemViewModel)obj).ShowNode(_filterText);
}
}
...
}
And a basic TreeViewItemViewModel:
public class ToolboxItemViewModel
{
...
public string Name { get; private set; }
public ObservableCollection<TreeViewItemViewModel> Children { get; private set; }
public bool ShowNode(string filterText)
{
... return true if filterText is contained in Name or has children that contain filterText ...
}
...
}
Everything is setup in the xaml so I see the treeview and search box.
When this code is exercised, the filter only applies to the Root nodes which is insufficient. Is there a way to make the filter trickle down in the hierarchy of nodes so that my predicate is called for every node ? In other words, can the filter be applied to the TreeView as a whole ?