Using a Scoped service to deal with stateful operations or maintaining data across multiple method calls

A common scenario in C# development where a scoped service would be used is when dealing with stateful operations or maintaining data across multiple method calls within the context of a single logical operation or request.

In web applications, each incoming HTTP request is typically processed in its own isolated scope. Services registered as scoped are instantiated once per request and are reused throughout the entire processing of that request. This behavior makes scoped services suitable for handling stateful operations within the context of a single request.

Let’s consider a common example of a shopping cart in an e-commerce web application. The shopping cart is an essential part of the user’s experience, and it requires maintaining the state of the user’s selected products throughout the user’s interaction with the website. A scoped service would be ideal for managing the shopping cart because:

1. Consistent State within a Request: A scoped service ensures that the same instance of the shopping cart is used throughout the entire processing of a single HTTP request. This allows various parts of the application (controllers, services, etc.) involved in processing the request to work with the same instance of the cart and maintain consistent state.
2. Isolation between Requests: Each incoming HTTP request will have its own instance of the shopping cart, which prevents data from one user’s request interfering with another user’s request. This ensures that users have their own personalized shopping experience without affecting other users.

Here’s an example of how you might define and use a scoped shopping cart service in a C# web application:

// Define the ShoppingCart class representing the user's shopping cart.
public class ShoppingCart
{
    public List<Product> Items { get; set; }

    public ShoppingCart()
    {
        Items = new List<Product>();
    }

    // Methods to add/remove items, calculate total, etc.
}

// Register the ShoppingCart as a scoped service in the ConfigureServices method of Startup class.
public void ConfigureServices(IServiceCollection services)
{
    // Other service registrations...

    services.AddScoped<ShoppingCart>();
}

Now, when a user makes an HTTP request to add items to their cart, you can inject the ShoppingCart service into the controller and use it to manage the cart for that specific request:

public class ShoppingCartController : Controller
{
    private readonly ShoppingCart _shoppingCart;

    public ShoppingCartController(ShoppingCart shoppingCart)
    {
        _shoppingCart = shoppingCart;
    }

    public IActionResult AddToCart(Product product)
    {
        _shoppingCart.Items.Add(product);
        return RedirectToAction("Cart");
    }

    public IActionResult Cart()
    {
        return View(_shoppingCart);
    }
}

In this example, the ShoppingCart service is created once per HTTP request, ensuring that the user’s shopping cart remains consistent and isolated during their interactions with the application.

Overall, using scoped services in C# development is crucial for managing stateful operations and providing a consistent and personalized experience to users within the context of a single request.