使用LINQ用XML在C＃中创建对象

Question

Hey so I'll start out by saying this is for an assignment...I have to create a console-based shopping cart that loads and saves to an XML file.

I can't quite work out how to load the XML file into objects/what the best way of doing this is....

 class Product
{
    public int RecordNumber { get; set; }
    public String Name { get; set; }
    public int Stock { get; set; }
    public int Price { get; set; }       
}
 class Cart
{

    public List<Product> items
    {
        get { return items; }
        set { items = value; }
    }

    public Cart() {}  //Right way to do constructor?

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

    public void RemoveProduct(Product prod)
    {
        items.Remove(prod);
    }
}

static void Main(string[] args)
    {
 XDocument XDoc = XDocument.Load("inventory.xml"); // Loading XML file
        var result = from q in XDoc.Descendants("product")
            select new Product
            {
                RecordNumber = Convert.ToInt32(q.Element("recordNumber").Value),
                Name = q.Element("name").Value,
                Stock = Convert.ToInt32(q.Element("stock").Value),
                Price = Convert.ToInt32(q.Element("price").Value)
            };

XML file is set up as follows (theres ten entries of products):

 <product>
    <recordNumber>1</recordNumber>
    <name>Floo Powder</name>
    <stock>100</stock>
    <price>5</price>
</product>

I have two questions here...Is my main method loading the XML file and creating 10 objects? If so, how do I access these objects?

Secondly, I was going to be adding Products to the cart, and then reducing the 'stock' figure, but when I think about it that seems wrong. Should I be creating an object for every single one of the stock available, and then adding them to the cart? Any advice on how I might be able to do that instead then?

Thanks so much!!

EDIT:

I am going to have to give the user of adding/removing stock to the cart as they wish. I imagine the code for doing that then would be something like, after displaying the details of all 10 objects (recordnumber, name, stock, price)

String input = Console.ReadLine();
foreach (var prod in result) {
  if (input == prod.recordnumber) {   // Assuming that user selects via indexnumber
   cart.AddProduct(//no idea what to put from here on
  }
}  

Am I on the right track?

Second EDIT:

String productNumber = Console.ReadLine();
int productInt = Convert.ToInt32(productNumber);

var match = from p in result
where p.RecordNumber == productInt
   select p;

 if (match != null)
 {
   ShoppingCart.AddProduct(??);  //what variable do I put in the parentheses?
                                 // Need to also reduce stock
 }
   else
 {
    // Inform user that no product exists
 }

As I said below, I'm totally at a loss as to what to put in the parentheses. i have tried match and p but obviously they're not right. Once I know how to refer to the object I should also be able to reduce the stock number for the object and put another instance into the list.

Thanks again for helping me out

Answer 1

Your program is loading 10 product items in the the result variable, and the it exits. To put them in the cart, you need to construct a Cart object, and add each product item to the cart:

static void Main(string[] args)
{
    XDocument XDoc = XDocument.Load("inventory.xml"); // Loading XML file
    var result = from q in XDoc.Descendants("product")
        select new Product
            {
                RecordNumber = Convert.ToInt32(q.Element("recordNumber").Value),
                Name = q.Element("name").Value,
                Stock = Convert.ToInt32(q.Element("stock").Value),
                Price = Convert.ToInt32(q.Element("price").Value)
             };

    var cart = new Cart();

    // Logic to add/remove/list cart here
}

To allow the user to add/remove items from the cart, you would need to have an identifier whether the add/remove/list, and the which item. This will have to be in a loop. You would probably also have an exit condition. So something in the lines of this:

var cmd = string.Empty;
do
{
    // Loop to allow the user to keep entering commands

    cmd = Console.ReadLine();        
    // if cmd == exit condition -> break;    
    // if cmd == list products condition -> write each prod to console
    // if cmd == add product condition -> Ask user to enter product number and add to cart
    // if cmd == remove product condition -> Ask user to enter product number and remove from cart
} while(true);

When the user enters the product number, you can find the correct product using linq:

var match = (from p in result
            where p.RecordNumber == productNumber
            select p).FirstOrDefault();

if (match != null)
{
    // Add/remove
}
else
{
    // Inform user that no product exists
}

Answer 2

You can use XmlSerializer :

var xmlSerializer = new XmlSerializer(typeof(List<Product>));

List<Product> productList;
using (var fileStreamReader = File.OpenRead("inventory.xml"));
{
    productList = (List<Product>) xmlSerializer.Deserialize(fileStreamReader);
}

Using LINQ 2 XML is ok, but if all you want to do is deserialize the XML into an object representation, serialization is easier.