Razor code

    var orderDetailsGrid = new GridModel("[Order Details]");
    orderDetailsGrid.Columns = new List
    {
        new GridColumn("OrderId", "Invoice Line ID") {ForeignKey = true },
        new GridColumn("ProductID", "Product")  {Lookup = new Lookup("Products","ProductID","ProductName")},
        new GridColumn("UNitPrice", "Price") { Format = "c"},
        new GridColumn("QUantity", "Quantity"),
        new GridColumn("UnitPrice*Quantity", "Cost") { Format = "c", DataType = typeof(Decimal)},
        new GridColumn("Discount", "Discount") { Format = "p"},
        new GridColumn( "UnitPrice*Quantity* (1-Discount)", "Net Cost") { Format = "c", DataType = typeof(Decimal)},
    };

    orderDetailsGrid.Caption = "Order Details";

    var ordersGrid = new GridModel(DataSourceType.SQLite, "Northwind", "Orders");
    ordersGrid.Columns = new List() {
        new GridColumn("OrderID") { PrimaryKey = true},
        new GridColumn("CustomerID") { ForeignKey = true, DataOnly = true},
        new GridColumn("EmployeeID")  { Lookup = new Lookup("Employees", "EmployeeID", "LastName || ',' || FirstName") },
        new GridColumn("OrderDate"),
        new GridColumn("RequiredDate"),
        new GridColumn("ShippedDate"),
        new GridColumn("ShipVia") { Lookup = new Lookup("Shippers", "ShipperId", "CompanyName") },
        new GridColumn("Freight") { Format = "c" },
        new GridColumn("ShipName"),
        new GridColumn("ShipAddress"),
        new GridColumn("ShipCity"),
        new GridColumn("ShipRegion"),
        new GridColumn("ShipPostalCode"),
        new GridColumn("ShipCountry")
    };

    ordersGrid.Caption = "Orders";
    ordersGrid.FixedFilter = "customerid = @customerid";
    ordersGrid.FixedFilterParameters.Add(new DbParameter("customerid", ""));
    ordersGrid.Bind(GridClientEvent.Initialised, "saveOrdersGridReference");

    ordersGrid.LinkedControl = orderDetailsGrid;

    var customersLevel = new TreeModel("Customers");
    customersLevel.Columns = new List() {
        new TreeColumn("CustomerID") {  },
        new TreeColumn("CompanyName") {  },
        new TreeColumn("Country") { ForeignKey = true }
    };

    var countriesLevel = new TreeModel("Customers");
    countriesLevel.Columns = new List() {
        new TreeColumn("Country") { PrimaryKey = true },
        new TreeColumn("Region") { ForeignKey = true }
    };
    countriesLevel.Distinct = true;
    countriesLevel.NestedLevel = customersLevel;

    var regionsTree = new TreeModel(DataSourceType.SQLite, "Northwind", "Customers");
    regionsTree.Columns = new List(){
        new TreeColumn("Region") { PrimaryKey = true }
    };

    regionsTree.NestedLevel = countriesLevel;
    regionsTree.Distinct = true;
    regionsTree.Expand = true;
    regionsTree.DropDown = false;
    regionsTree.MaxHeight = "70rem";

    regionsTree.Bind(TreeClientEvent.ItemSelected, "customerSelected");
   

    <div style="display:flex;flex-direction:row;gap: 10px;">
        <div>
            @(await DbNetSuiteCore.Control.Create(HttpContext).Render(regionsTree))
        </div>
        <div style="display:flex;flex-direction:column;gap: 10px;padding-top:5px;">
            <div>
                @(await DbNetSuiteCore.Control.Create(HttpContext).Render(ordersGrid))
            </div>
            <div>
                @(await DbNetSuiteCore.Control.Create(HttpContext).Render(orderDetailsGrid))
            </div>
        </div>
    </div>