How to serialize/deserialize simple classes to XML and back

Sometimes I want to emulate stored data of my classes without setting up a round trip to the database. For example, let's say I have开发者_StackOverflow the following classes:

public class ShoppingCart
{
    public List<CartItem> Items {get; set;}
    public int UserID { get; set; }
}

public class CartItem
{
    public int SkuID { get; set; }
    public int Quantity  { get; set; }
    public double ExtendedCost  { get; set; }
}

Let's say I build a ShoppingCart object in memory and want to "save" it as an XML document. Is this possible via some kind of XDocument.CreateFromPOCO(shoppingCart) method? How about in the other direction: is there a built-in way to create a ShoppingCart object from an XML document like new ShoppingCart(xDoc)?

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XmlSerializer is one way to do it. DataContractSerializer is another. Example with XmlSerializer:

using System.Xml;
using System.Xml.Serialization;

//...

ShoppingCart shoppingCart = FetchShoppingCartFromSomewhere();
var serializer = new XmlSerializer(shoppingCart.GetType());
using (var writer = XmlWriter.Create("shoppingcart.xml"))
{
    serializer.Serialize(writer, shoppingCart);
}

and to deserialize it back:

var serializer = new XmlSerializer(typeof(ShoppingCart));
using (var reader = XmlReader.Create("shoppingcart.xml"))
{
    var shoppingCart = (ShoppingCart)serializer.Deserialize(reader);
}

Also for better encapsulation I would recommend you using properties instead of fields in your CartItem class.

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Nicely done. Here is the example to serialize plain POCO to string.

    private string poco2Xml(object obj)
    {
        XmlSerializer serializer = new XmlSerializer(obj.GetType());
        StringBuilder result = new StringBuilder();
        using (var writer = XmlWriter.Create(result))
        {
            serializer.Serialize(writer, obj);
        }
        return result.ToString();
    }

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You could serialize/deserialize with either the XmlSerializer or the DataContractSerializer.

Annotate your classes with DataContract and DataMember attributes and write something like this to serialize to xml to a file.

ShoppingCart cart = ...
using(FileStream writer = new FileStream(fileName, FileMode.Create))
{
   DataContractSerializer ser = new DataContractSerializer(typeof(ShoppingCart));
   ser.WriteObject(writer, cart);
}

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Just mark up what you want to serialize with [XmlElement(name)] (or XmlAttribute, XmlRoot, etc) and then use the XmlSerializer. If you need really custom formating, implement IXmlSerializable.