<TelerikMultiColumnComboBox Data="_orders"
                                                            AllowCustom="true"
                                                            Value="_selectedOrder"
                                                            ValueExpression="(() => _selectedOrder)"
                                                            ValueChanged="@(async (string order) => await OrderValueChangedAsync(order))"
                                                            OnChange="OrderChangedHandler"
                                                            ValueField="@nameof(OrderDto.Id)"
                                                            TextField="@nameof(OrderDto.OrderNumber)">
                                    <MultiColumnComboBoxColumns>
                                        <MultiColumnComboBoxColumn Field="@nameof(OrderDto.Source)" Title="Source"></MultiColumnComboBoxColumn>
                                        <MultiColumnComboBoxColumn Field="@nameof(OrderDto.DeliverOn)" Title="Deliver On"></MultiColumnComboBoxColumn>
                                        <MultiColumnComboBoxColumn Field="@nameof(OrderDto.OrderNumber)" Title="Order Number"></MultiColumnComboBoxColumn>
                                        <MultiColumnComboBoxColumn Field="@nameof(OrderDto.Suffix)" Title="Suffix"></MultiColumnComboBoxColumn>
                                    </MultiColumnComboBoxColumns>
                                    <MultiColumnComboBoxSettings>
                                        <MultiColumnComboBoxPopupSettings Width="600px" />
                                    </MultiColumnComboBoxSettings>
                                </TelerikMultiColumnComboBox>

private string _selectedOrder;

        private async Task OrderValueChangedAsync(string orderNumber)
        {
            try
            {
                Console.WriteLine($"ValueChanged fired with value {orderNumber}");

                if (orderNumber == null || orderNumber.Length < 5)
                {
                    _orders = new(); // Don't load orders until the user has typed in at least 4 characters so we don't bring back too many orders
                    return;
                }

                if (_activity.Type == "C")
                {
                    _orders = await APIService.CallAPIAsync<List<OrderDto>>($"RMOActivity/GetSalesOrders?orgCode={AppState.SelectedDivision.OrgCode}&orderNumber={orderNumber}", null, HttpMethod.Get);
                }
                else
                {
                    _orders = await APIService.CallAPIAsync<List<OrderDto>>($"RMOActivity/GetPurchaseOrders?orgCode={AppState.SelectedDivision.OrgCode}&purchaseOrderNumber={orderNumber}", null, HttpMethod.Get);
                }
            }
            catch (Exception e)
            {
                LogError("Error loading orders", e);
            }
            finally
            {
                Console.WriteLine($"ValueChanged finished with value {orderNumber}");
            }
        }

        private void OrderChangedHandler(object order)
        {
            try
            {
                Console.WriteLine($"OnChange fired with value {(order == null ? "null" : order.ToString())}");
                if (order != null)
                {
                    _selectedOrder = (string)order;
                }
                Console.WriteLine($"OnChange finished with value {(order == null ? "null" : order.ToString())}");
            }
            catch (Exception e)
            {
                LogError("Error loading order", e);
            }
        }

    public class OrderDto
    {
        public int Id { get; set; }
        public string Source { get; set; }
        public DateOnly? DeliverOn { get; set; }
        public string OrderNumber { get; set; }
        public string Suffix { get; set; }
        public string CustomerOrVendorNumber { get; set; }
        public string ShipToOrVendorCode { get; set; }
    }

@page "/"
<TelerikTreeView Data="@FlatData"
                 CheckBoxMode="@TreeViewCheckBoxMode.Multiple"
                 CheckParents="@true"
                 CheckChildren="@true"
                 CheckOnClick="@false"
                 @bind-CheckedItems="@SelectedItems">
    
</TelerikTreeView>

@code {
    List<TreeItem> FlatData { get; set; }
    IEnumerable<object> SelectedItems { get; set; } = new List<object>();
    protected override async Task OnInitializedAsync()
    {
        await GenerateData();
        await SelectDefault();
    }

    async Task SelectDefault()
    {
        await Task.Delay(100);
        SelectedItems = FlatData.Where(data => data.Id == 2);
    }

    async Task GenerateData()
    {
        FlatData = new List<TreeItem>();

        FlatData.Add(new TreeItem()
        {
            Id = 1,
            Text = "Project",
            ParentId = null,
            HasChildren = true,
            Icon = "folder",
            Expanded = true
        });

        FlatData.Add(new TreeItem()
        {
            Id = 2,
            Text = "Design",
            ParentId = 1,
            HasChildren = true,
            Icon = "brush",
            Expanded = true
        });
        FlatData.Add(new TreeItem()
        {
            Id = 3,
            Text = "Implementation",
            ParentId = 1,
            HasChildren = true,
            Icon = "folder",
            Expanded = true
        });
    }

    public class TreeItem
    {
        public int Id { get; set; }
        public string Text { get; set; }
        public int? ParentId { get; set; }
        public bool HasChildren { get; set; }
        public string Icon { get; set; }
        public bool Expanded { get; set; }
    }
}