public IActionResult Index()

{

    // Populate the initial dropdown data

    ViewBag.Categories = _yourCategoryService.GetCategories(); // Replace with your actual category fetching logic

​

    return View();

}

​

[HttpGet]

public JsonResult GetSubcategories(int categoryId)

{

    // Retrieve subcategories based on the selected category ID

    var subcategories = _yourSubcategoryService.GetSubcategoriesByCategory(categoryId); // Replace with your actual subcategory fetching logic

​

    return Json(subcategories);

}