Razor code

var customerColumns = new List
{
    new GridColumn("customerid", "CustomerID") {PrimaryKey = true },
    new GridColumn("firstname", "Forename"),
    new GridColumn("lastname", "Surname"),
    new GridColumn("email", "Email Address") {Format = FormatType.Email },
    new GridColumn("address", "Address"),
    new GridColumn("city", "City") { InitialSortOrder = SortOrder.Desc},
    new GridColumn("postalcode", "Post Code")
};

var invoiceColumns = new List
{
    new GridColumn("invoiceid", "Invoice ID") {PrimaryKey = true },
    new GridColumn("customerid", "Customer ID") {ForeignKey = true, DataOnly = true },
    new GridColumn("invoicedate", "Date"),
    new GridColumn("billingaddress", "Address"),
    new GridColumn("billingcity", "City"),
    new GridColumn("billingstate", "State"),
    new GridColumn("billingcountry", "Country"),
    new GridColumn("billingpostalcode", "Post Code")
};

var invoiceItemColumns = new List
{
    new GridColumn("invoicelineid", "Line ID"),
    new GridColumn("invoiceid", "Invoice ID") {ForeignKey = true, DataOnly = true },
    new GridColumn("trackid", "Track ID") {Lookup = new Lookup("tracks","trackid","name")},
    new GridColumn("unitprice", "Price") {Format = "C"},
    new GridColumn("quantity", "Qty")
};

var invoiceLineGrid = new GridModel("Invoice_items");
invoiceLineGrid.Columns = invoiceItemColumns;
invoiceLineGrid.Caption = "Invoice Lines";
invoiceLineGrid.PageSize = 5;
invoiceLineGrid.ToolbarPosition = ToolbarPosition.Hidden;

var invoiceGrid = new GridModel("Invoices");
invoiceGrid.Columns = invoiceColumns;
invoiceGrid.LinkedGrid = invoiceLineGrid;
invoiceGrid.Caption = "Invoices";
invoiceGrid.PageSize = 5;
invoiceGrid.ToolbarPosition = ToolbarPosition.Hidden;

var customerGrid = new GridModel(DataSourceType.SQLite, "Chinook(sqlite)", "Customers");
customerGrid.Columns = customerColumns;
customerGrid.LinkedGrid = invoiceGrid;
customerGrid.PageSize = 5;

@(await new DbNetSuiteCore.GridControl(HttpContext).Render(customerGrid))
@(await new DbNetSuiteCore.GridControl(HttpContext).Render(invoiceGrid))
@(await new DbNetSuiteCore.GridControl(HttpContext).Render(invoiceLineGrid))