我正在尝试查找所选项目的小计

Question

I have the prices of the items in an array:

double[] productPriceArray = { 1162.99, 399.99, 329.99, 199.99, 149.99 };

I am trying to find the total of the ones that a user puts in a "cart". I'm not sure how to go about that. I know I can use the line of code:

subtotal = productCostArray[lbxCart.SelectedIndex];  
lblSubtotal.Text = subtotal.ToString("c"); 

to find the total of one of the indices, but how can I find the total of multiple indices?

Thanks!

Answer 1

There is no way in the current design , You need atleast a list of product and product price mapping then you need a list of products in the cart and in the cart class you can define a function to get the subtotal of all products.

public class  Product
{
    public string ProductId { get; set; }

    public string ProductName { get; set; }

    public double Price { get; set; }
}

public class ShoppingCart
{
    public string CartId { get; set; }

    public List<Product> Products { get; set; }

    public void AddProductToCart(Product p)
    {
        if(Products==null)
            Products = new List<Product>();
         if(p!=null)
                 Products.Add(p);

    }

    public double CartPrice()
    {
        return Products != null ? Products.Sum(p => p.Price):0D;
    }
}

and usage

 var shopCart = new ShoppingCart();
        shopCart.AddProductToCart(new Product {ProductId = "1",Price = 12.09, ProductName = "P1"});
          shopCart.AddProductToCart(new Product {ProductId = "2",Price = 11.09, ProductName = "P2"});
        MessageBox.Show(shopCart.CartPrice().ToString());

Answer 2

如果您有一个选定项目索引的列表（如您的示例所示），则可以执行以下操作：

var subtotal = SelectedIndices.Select(idx => productPriceArray[idx]).Sum();