What should I do if the data is not saved when clicking on Add in this layout?

Question

ASP.NET

Performance:

@model IEnumerable<Product>
<h3 class="p-2 bg-primary text-white text-center">Products</h3>
<div class="container-fluid mt-3">
    <div class="row">
        <div class="col font-weight-bold">Name</div>
        <div class="col font-weight-bold">Category</div>
        <div class="col font-weight-bold">Purchase Price</div>
        <div class="col font-weight-bold">Retail Price</div>
        <div class="col"></div>
    </div>
    <form asp-action="AddProduct" method="post">
        <div class="row">
            <div class="col"><input name="Name" class="form-control" /></div>
            <div class="col"><input name="Category" class="form-control" /></div>
            <div class="col">
                <input name="PurchasePrice" class="form-control" />
            </div>
            <div class="col">
                <input name="RetailPrice" class="form-control" />
            </div>
            <div class="col">
                <button type="submit" class="btn btn-primary">Add</button>
            </div>
        </div>
    </form>
    @if (Model.Count() == 0)
    {
        <div class="row">
            <div class="col text-center p-2">No Data</div>
        </div>
    }
    else
    {
       @foreach (Product p in Model)
        {
            <div class="row p-2">
                <div class="col">@p.Name</div>
                <div class="col">@p.Category</div>
                <div class="col text-right">@p.PurchasePrice</div>
                <div class="col text-right">@p.RetailPrice</div>
                <div class="col"></div>
            </div>
        }
    }
</div>

Model:

public class DataRepository : IRepository
    {
        private List<Product> data = new List<Product>();
        public IEnumerable<Product> Products => data;
        public void AddProduct(Product product)
        {
            this.data.Add(product);
        }
    }

public interface IRepository
    {
        public IEnumerable<Product> Products { get; }
        void AddProduct(Product product);
    }

Controller:

public class HomeController : Controller
    {
        private IRepository repository;
        public HomeController(IRepository repo) => repository = repo;

        public IActionResult Index() => View(repository.Products);

        [HttpPost]
        public IActionResult AddProducts(Product product)
        {
            repository.AddProduct(product);
            return RedirectToAction(nameof(Index));

        }      
    }

public void ConfigureServices(IServiceCollection services)
        {
            services.AddRazorPages();
            services.AddMvc();
            services.AddSingleton<IRepository, DataRepository>();
        }

Answer 1

Where are you actually saving it? to a repository that saves the data to a list, which is then deleted when the controller action exits. The data must be stored in a database.