CODEWITHSUNDEEP
silverlightdata-bindingmvvmtreeview
Jarvis
Jarvis

Reputation: 81

Expand Root in TreeView when ItemSource changed

I have a ChildWindow in a Silverlight 4 App with a TreeView. The ItemSource is binded to an ObservableCollection of Items in a ViewModel. When the window opens the item are loaded from a webservice.

I have only one root node and I need it to be initially expanded. The TreeView even has the extension ExpandToDepth() which seems perfect but I don't know where I can call it. I didn't find an event that occurs after the items are updated from the ItemSource.

I tried using ItemContainerGenerator.ItemChanged and OnItemsChanged in TreeView but they are both executed before the tree view items are generated so the expand commands won't work.

How can I get this to work?

Upvotes: 1

Views: 1190

Answers (3)

Jarvis
Jarvis

Reputation: 81

I solved my problem by overriding the PrepareContainerForItemOverride method in TreeView. I wondered why this is just called for the root node but it works.

public class ExpandedRootTreeView : TreeView
{
    protected override void PrepareContainerForItemOverride(DependencyObject element, object item)
    {
        TreeViewItem treeViewItem = element as TreeViewItem;

        if (treeViewItem != null) treeViewItem.IsExpanded = true;

        base.PrepareContainerForItemOverride(element, item);
    }
}

Thanks to everybody who responded.

Upvotes: 0

Nario
Nario

Reputation: 551

Derive from TreeView and create IsRootItemExpanded property and create same name property in ViewModel. In set accesser check if value true then call your method like this ExpandToDepth(1) When itemssource is need to update then set IsRootItemExpanded property true. You must to bind IsRootItemExpanded of TreeView to IsRootItemExpanded of ViewModel.

Upvotes: 0

Sonosar
Sonosar

Reputation: 526

Try to register for your ObservableCollection's CollectionChange Event and do your actions there.

Upvotes: 1

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