在哪里实现.NET核心Web API中的业务逻辑？

// 业务逻辑接口
public interface IProductService
{
    IEnumerable<Product> GetProducts();
    Product GetProductById(int id);
    void AddProduct(Product product);
    void UpdateProduct(int id, Product product);
    void DeleteProduct(int id);
}

// 业务逻辑实现
public class ProductService : IProductService
{
    private readonly List<Product> _products;

    public ProductService()
    {
        _products = new List<Product>();
    }

    public IEnumerable<Product> GetProducts()
    {
        return _products;
    }

    public Product GetProductById(int id)
    {
        return _products.FirstOrDefault(p => p.Id == id);
    }

    public void AddProduct(Product product)
    {
        _products.Add(product);
    }

    public void UpdateProduct(int id, Product product)
    {
        var existingProduct = _products.FirstOrDefault(p => p.Id == id);
        if (existingProduct != null)
        {
            existingProduct.Name = product.Name;
            existingProduct.Price = product.Price;
        }
    }

    public void DeleteProduct(int id)
    {
        var existingProduct = _products.FirstOrDefault(p => p.Id == id);
        if (existingProduct != null)
        {
            _products.Remove(existingProduct);
        }
    }
}

// 控制器
[ApiController]
[Route("api/products")]
public class ProductsController : ControllerBase
{
    private readonly IProductService _productService;

    public ProductsController(IProductService productService)
    {
        _productService = productService;
    }

    [HttpGet]
    public IActionResult GetProducts()
    {
        var products = _productService.GetProducts();
        return Ok(products);
    }

    [HttpGet("{id}")]
    public IActionResult GetProductById(int id)
    {
        var product = _productService.GetProductById(id);
        if (product == null)
        {
            return NotFound();
        }
        return Ok(product);
    }

    [HttpPost]
    public IActionResult AddProduct(Product product)
    {
        _productService.AddProduct(product);
        return CreatedAtAction(nameof(GetProductById), new { id = product.Id }, product);
    }

    [HttpPut("{id}")]
    public IActionResult UpdateProduct(int id, Product product)
    {
        _productService.UpdateProduct(id, product);
        return NoContent();
    }

    [HttpDelete("{id}")]
    public IActionResult DeleteProduct(int id)
    {
        _productService.DeleteProduct(id);
        return NoContent();
    }
}