ProductService.cs

public interface IProductService
{
    List<string> GetProductNames();
}

public class ProductService : IProductService
{
    public List<string> GetProductNames()
    {
        return new List<string>
        {
            "chai",
            "chang",
            "aniseed-syrup",
            "chef-antons-cajun-seasoning",
            "chef-antons-gumbo-mix",
            "grandmas-boysenberry-spread",
            "uncle-bobs-organic-dried-pears",
            "northwoods-cranberry-sauce",
            "mishi-kobe-niku"
        };
    }
}