How to programmatically select an item in a WPF TreeView?

It's a real pain for some strange reason, you have to use ContainerFromItem to get the container, then invoke the select method.

//  selectedItemObject is not a TreeViewItem, but an item from the collection that 
//  populated the TreeView.

var tvi = treeView.ItemContainerGenerator.ContainerFromItem(selectedItemObject) 
          as TreeViewItem;

if (tvi != null)
{
    tvi.IsSelected = true;
}

There once was a blog entry on how to do it here, but the link is dead now.

You need to get the TreeViewItem and then set IsSelected to true.

The proposed answer doesn't work. @fandisusanto's answer probably does work, but it can be made simpler. This is the simplest answer I can come up with:

    private static void DeselectTreeViewItem(IEnumerable<TreeViewItem> treeViewItems)
    {
        foreach (var treeViewItem in treeViewItems)
        {
            if (treeViewItem.IsSelected)
            {
                treeViewItem.IsSelected = false;
                return;
            }

            DeselectTreeViewItem(treeViewItem.Items.Cast<TreeViewItem>());
        }
    }

Usage:

    private void ClearSelectedItem()
    {
        if (AssetTreeView.SelectedItem != null)
        {
            DeselectTreeViewItem(AssetTreeView.Items.Cast<TreeViewItem>());
        }
    }

This is my solution. The others failed for me in various ways. You need to walk the tree from top to bottom, looking for the tree item at each level, expanding and updating the layout along the way.

This function takes a stack of nodes where the first one out of the stack is the top most node, and each subsequent node on the stack is a child of the previous parent. The second argument is the TreeView.

As each item is found, that item is expanded, and the final item is returned, where the caller can select it.

    TreeViewItem FindTreeViewItem( Stack<object> nodeStack, TreeView treeView )
    {
        ItemsControl itemsControl = treeView;

        while (nodeStack.Count > 0) {
            object node = nodeStack.Pop();
            bool found = false;

            foreach (object item in itemsControl.Items) {
                if (item == node) {
                    found = true;

                    if (itemsControl.ItemContainerGenerator.ContainerFromItem( item ) is TreeViewItem treeViewItem) {
                        if (nodeStack.Count == 0) {
                            return treeViewItem;
                        }

                        itemsControl = treeViewItem;
                        treeViewItem.IsExpanded = true;
                        treeViewItem.UpdateLayout();
                        break;
                    }
                }
            }

            if (!found) {
                return null;
            }
        }

        return null;
    }

Example of how to call it:

    // Build nodeStack here from your data

    TreeViewItem treeViewItem = FindTreeViewItem( nodeStack, treeView );

    if (treeViewItem != null) {
        treeViewItem.IsSelected = true;
        treeViewItem.BringIntoView();
    }

I wrote a Helper class for this, which supports MVVM and lazy loaded items.

public class TreeViewHelper<TModel>
{
    public TreeViewHelper(TreeView treeView, Func<TModel, TModel> getParent, Func<TModel, IList<TModel>> getSubItems)
    {
        TreeView = treeView;
        GetParent = getParent;
        GetSubItems = getSubItems;
    }

    public TreeView TreeView { get; }
    public Func<TModel, TModel> GetParent { get; }
    public Func<TModel, IList<TModel>> GetSubItems { get; }

    public void SelectItemWhileLoaded(TModel node, IList<TModel> rootNodes)
    {
        if (TreeView.IsLoaded)
        {
            SelectItem(node, rootNodes);
        }
        else
        {
            TreeView.Loaded += TreeView_Loaded;
            void TreeView_Loaded(object sender, System.Windows.RoutedEventArgs e)
            {
                TreeView.Loaded -= TreeView_Loaded;
                SelectItem(node, rootNodes);
            }
        }
    }


    public void SelectItem(TModel node, IList<TModel> rootNodes)
    {
        Stack<TModel> nodes = new Stack<TModel>();
        //push into stack
        while (!rootNodes.Contains(node))
        {
            nodes.Push(node);
            node = GetParent(node);
        }
        TreeViewItem treeViewItem = TreeView.ItemContainerGenerator
            .ContainerFromItem(node) as TreeViewItem;
        if (nodes.Count == 0)
        {
            //Top level
            treeViewItem.IsSelected = true;
            treeViewItem.BringIntoView();
            return;
        }
        Expanded(true);
        void Expanded(bool top)
        {
            if (!top)
            {
                treeViewItem = treeViewItem.ItemContainerGenerator
                    .ContainerFromItem(node) as TreeViewItem;
                if (nodes.Count == 0)
                {
                    treeViewItem.IsSelected = true;
                    treeViewItem.BringIntoView();
                    return;
                }
            }
            node = nodes.Pop();
            treeViewItem.IsExpanded = true;
            if (treeViewItem.ItemContainerGenerator.Status == GeneratorStatus.ContainersGenerated)
            {
                Expanded(true);
            }
            else
            {
                //Lazy
                treeViewItem.ItemContainerGenerator.StatusChanged += ItemContainerGenerator_StatusChanged;
            }
        }
        void ItemContainerGenerator_StatusChanged(object sender, EventArgs e)
        {
            if (treeViewItem.ItemContainerGenerator.Status == GeneratorStatus.ContainersGenerated)
            {
                treeViewItem.ItemContainerGenerator.StatusChanged -= ItemContainerGenerator_StatusChanged;
                Expanded(false);
            }
        }
    }
}

I think this is the simplest solution:

private void MouseDownEventProcessing(TreeNodeMouseClickEventArgs e)
{
    tvEmployeeDirectory.SelectedNode = e.Node;
}