Question

I am trying to implement MVVM, and are having issues with moving LoadOnDemand to my ViewModel using triggers and RelayCommands, I have the event firing and all,
but as it turns out it is possible to expand a node in the tree without having it selected (i have databound the SelectedItem property in my ViewModel), thus breaking the logic, since the onLoad animation will continue to spin.

If I instead do this:

private void HierarchyTreeControl_LoadOnDemand(
                   Object sender, 
                   Telerik.Windows.RadRoutedEventArgs e){ 
RadTreeViewItem clickedItem = null;  
clickedItem = e.OriginalSource as  RadTreeViewItem;
if (clickedItem != null)  {  
...do load logic

in the code behind file. I have access to the expanding item (clickedItem). What am I missing?

Is it possible to do some sort of binding on the ExandingItem?

Any Help will be appreciated 🙂

Answer 1

Since you are not using a standard treeview, I cannot be sure this is relevant. But I have previously had success in binding a TreeViewItem’s IsExpanded property to a viewmodel property, in which I loaded items when the value was set to true (and not already loaded).

Here is a useful link: One more platform difference more-or-less tamed