Putting it together

Combine the cart class with a console menu.

Putting it together

The Cart class is fully ready; in the final step we will handle a menu of commands with a switch. Main iterates over a command array with foreach; for each command the switch picks the right branch.

The commands are English keywords: list lists the products, total prints the subtotal, exit prints a goodbye message. This way a single loop combines every cart feature in one place.

foreach and switch together

Walking a list of commands with foreach and handling each with switch builds the core of a small console app. The cart.Items property lets you walk the cart contents from outside.

The list branch prints each product with foreach (var p in cart.Items); the total branch calls cart.GetSubtotal(); the exit branch prints a goodbye message. Each branch ends with break.

Exercise Write the switch menu

Inside Main's foreach (string command in commands) body, write a switch (command). Have three branches: case "list": walks cart.Items with foreach and prints each product as $"{p.Name} - {p.Quantity} x {p.Price} = {p.Quantity * p.Price}"; case "total": prints $"Total: {cart.GetSubtotal()}"; case "exit": prints "bye". Each branch ends with break.

Show example solution

...; break; case "total": ...; break; case "exit": ...; break; }
Example solution:
using System;
using System.Collections.Generic;

class Product
{
    public string Name { get; set; }
    public double Price { get; set; }
    public int Quantity { get; set; }
}

class Cart
{
    private List<Product> items = new List<Product>();
    public List<Product> Items => items;

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

    public void UpdateQuantity(string name, int quantity)
    {
        foreach (var p in items) if (p.Name == name) p.Quantity = quantity;
    }

    public void RemoveProduct(string name)
    {
        for (int i = items.Count - 1; i >= 0; i--)
            if (items[i].Name == name) items.RemoveAt(i);
    }

    public double GetSubtotal()
    {
        double sum = 0;
        foreach (var p in items) sum += p.Price * p.Quantity;
        return sum;
    }
}

class Program
{
    static void Main()
    {
        var cart = new Cart();
        cart.AddProduct(new Product { Name = "Notebook", Price = 25, Quantity = 2 });
        cart.AddProduct(new Product { Name = "Pen", Price = 10, Quantity = 3 });

        string[] commands = { "list", "total", "exit" };
        foreach (string command in commands)
        {
            switch (command)
            {
                case "list":
                    foreach (var p in cart.Items)
                        Console.WriteLine($"{p.Name} - {p.Quantity} x {p.Price} = {p.Quantity * p.Price}");
                    break;
                case "total":
                    Console.WriteLine($"Total: {cart.GetSubtotal()}");
                    break;
                case "exit":
                    Console.WriteLine("bye");
                    break;
            }
        }
    }
}

Test yourself

What does 'case "list":' mean inside switch (command)?
```
switch (command)
{
    case "list":
        // ...
        break;
}
```
- The list is empty
- Only the list feature
- This branch runs when command is 'list'
- List all commands
Show answer

This branch runs when command is 'list' — Correct. case "list": matches only when command is 'list'.
Match each command to its job

list

Lists the products
total

Returns the subtotal
exit

Prints a goodbye message
default

Unknown command

Write the case label

switch (command)
{
    ____
        Console.WriteLine($"Total: {cart.GetSubtotal()}");
        break;
}

Show answer

switch (command)
{
    case "total":
        Console.WriteLine($"Total: {cart.GetSubtotal()}");
        break;
}

Next lesson: Declaring arrays

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