Hello,

Here is your code of the example "how to load hierarchical data on demand" with the option FilterMode = "@ TreeListFilterMode.FilterMenu"
As you can see if we click on a node the whole hierarchy disappears. if you remove this option all work fine

 

@* this sample shows how to load hierarchical data on demand and one way of handling no data being returned. Depending on your models and data logic you may have to tweak some checks, review the code comments for details.

*@

<TelerikTreeList Data="@Data"
                 ItemsField="@(nameof(Employee.DirectReports))"
                 HasChildrenField="@(nameof(Employee.HasChildren))"
                 OnExpand="@OnExpandHandler"
                 Pageable="true" Width="550px" Height="400px" FilterMode="@TreeListFilterMode.FilterMenu" >
    <TreeListColumns>
        <TreeListColumn Field="Name" Expandable="true" Width="220px" />
        <TreeListColumn Field="HireDate" Width="120px" />
    </TreeListColumns>
</TelerikTreeList>

@code {
    public List<Employee> Data { get; set; }

    // load on demand through the event
    async Task OnExpandHandler(TreeListExpandEventArgs args)
    {
        Employee item = args.Item as Employee;
        if (item.HasChildren && // it is marked as having children
            (item.DirectReports == null || item.DirectReports.Count == 0) // there are no child items
            )
        {
            // request data
            var children = await GetChildren(item);

            if (children.Count > 0)
            {
                // child items exist - add them to the current item
                item.DirectReports = children;
            }
            else
            {
                // no nested data - hide the expand arrow
                item.HasChildren = false;
            }
        }
    }

    async Task<List<Employee>> GetChildren(Employee itm)
    {
        await Task.Delay(400); // simulate delay. Remove for a real app

        List<Employee> data = new List<Employee>();

        // to showcase an example of when no actual child items are returned
        // we will check for too long nesting chain with this simpe logic
        if (itm.Name.LastIndexOf("Child of") < 15)
        {
            data.Add(new Employee
            {
                Name = "Child of " + itm.Name,
                HasChildren = true
            });
        }

        return await Task.FromResult(data);
    }

    // sample model

    public class Employee
    {
        // hierarchical data collections
        public List<Employee> DirectReports { get; set; }
        public bool HasChildren { get; set; }

        // data fields for display
        public string Name { get; set; }
        public DateTime HireDate { get; set; }
    }

    // initial data generation

    protected override async Task OnInitializedAsync()
    {
        List<Employee> data = new List<Employee>();
        for (int i = 0; i < 6; i++)
        {
            data.Add(new Employee
            {
                Name = $"root: {i}",
                HireDate = DateTime.Now.AddYears(-i),
                HasChildren = true
            });
        }

        // mark an item as non-expandable (not having children)
        data[1].HasChildren = false;
        data[1].Name += "(not expandable) ";

        Data = data;
    }
}