@using System.Collections.ObjectModel

<TelerikButton Primary="true" OnClick="CreateItem">Create item</TelerikButton>

<TelerikButton Primary="true" OnClick="DeleteItem">Delete item</TelerikButton>

<TelerikTreeView Data="@TreeData">
</TelerikTreeView>

@code {
    private void CreateItem()
    {
        TreeData[0].Items.Add(new TreeItem()
        {
            Text = "My item",
            HasChildren = false,
            Expanded = false
        });
    }

    private void DeleteItem()
    {
        if(TreeData[0].Items.Count > 0)
            TreeData[0].Items.RemoveAt(TreeData[0].Items.Count - 1);
    }

    public ObservableCollection<TreeItem> TreeData { get; set; }

    public class TreeItem
    {
        public string Text { get; set; }
        public ObservableCollection<TreeItem> Items { get; set; } = new ObservableCollection<TreeItem>();
        public bool Expanded { get; set; }
        public bool HasChildren { get; set; }
        public bool Selected { get; set; }

    }

    protected override void OnInitialized()
    {
        LoadHierarchical();
    }

    private void LoadHierarchical()
    {
        ObservableCollection<TreeItem> roots = new ObservableCollection<TreeItem>() {
            new TreeItem { Text = "Item 1", Expanded = true, HasChildren = true },
            new TreeItem { Text = "Item 2", HasChildren = true }
        };

        roots[0].Items.Add(new TreeItem
        {
            Text = "Item 1 first child",

        });

        roots[0].Items.Add(new TreeItem
        {
            Text = "Item 1 second child",

        });

        roots[1].Items.Add(new TreeItem
        {
            Text = "Item 2 first child",

        });

        roots[1].Items.Add(new TreeItem
        {
            Text = "Item 2 second child",

        });

        TreeData = roots;
    }
}