Treeview Refresh

[Matthew Cartwright]

In my application I have hierarchical, load on demand data. My view auto-refreshes every 60 seconds and I want the treeview to maintain it's expanded items, the selected item and also the scroll position.

What is the recommended approach for refreshing a tree and maintaining state?

Thanks

[Kiril Stanoev]

Hello Matthew,

Have you considered using ContainerBindings along with your HierarchicalData. ContainerBindings allow you to bind a property of the container(RadTreeViewItem's IsSelected, CheckState, IsExpanded etc.) to a property in your model. I am attaching a sample project that demonstrates the usage of ContainerBindings. Also, in my project I refresh the data in the treeview every 5 seconds. Have a look at the example and if something is unclear or you have additional questions, let me know.

Regards,
Kiril Stanoev
the Telerik team

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[Matthew Cartwright]

Upon first view it looks like a really good idea, but then thinking about it this requires that my data-model is altered for specific support of the telerik treeview - which then seems like a really bad idea. Maybe extension methods would fill this gap, or inherited objects specifically for use on the treeview...hmmmm...

[Kiril Stanoev]

Hi Matthew,

In my opinion, using ContainerBindings is not necessarily bad idea. Actually they are really close to the ViewModel from the MVVM pattern.

Another way to achieve what you are looking is to use RadTreeView's GetItemByPath(). The main idea is the following: Every item keeps full path(string) to the root of the tree. Every time an item is selected or expanded, you add the full path of the item to some collection(ObservableCollection<string>). After you refresh, you iterate through the list of selected/expanded items and use GetItemByPath to select/expand the item:

// go through all selected items and make the treeview select them
foreach (string itemPath in selectedItems.ToList())
{
    if (treeView1.GetItemByPath(itemPath, "|") != null)
    {
        treeView1.GetItemByPath(itemPath, "|").IsSelected = true;
    }
}

// go through all expanded items and make the treeview select them
foreach (string itemPath in expandedItems.ToList())
{
    if (treeView1.GetItemByPath(itemPath, "|") != null)
    {
        treeView1.GetItemByPath(itemPath, "|").IsExpanded = true;
    }
}

The attached sample project demonstrates how your business objects can build full path. Have a look at it and let me know how this works for you.
Once again, I'd recommend you use the ContainerBindings approach, since if you compare the 2 projects, you will agree that the first one(with ContainerBindings) is much cleaner and easy to maintain.
Let me know which approach you favor.

Regards,
Kiril Stanoev
the Telerik team

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Watch a video on how to optimize your support resource searches and check out more tips on the blogs.