<div>
    <TelerikPanelBar Data="@Items">
        <PanelBarBindings>
            <PanelBarBinding>
                <ContentTemplate>
                    @{
                        var item = context as PanelBarItem;
                        <div>
                            <TelerikTextBox @bind-Value="item.Text"></TelerikTextBox>
                        </div>
                    }
                </ContentTemplate>
            </PanelBarBinding>
        </PanelBarBindings>
    </TelerikPanelBar>
</div>

@code {
    public List<PanelBarItem> Items { get; set; }

    public class PanelBarItem
    {
        public string Text { get; set; }
        public List<PanelBarItem> Items { get; set; }
    }

    protected override void OnInitialized()
    {
        Items = new List<PanelBarItem>()
    {
            new PanelBarItem() { Text = "Item 1" },
            new PanelBarItem() { Text = "Item 2" }
        };
        base.OnInitialized();
    }
}