In my article Google Checkout XSD File To Generate .Net class I explained how you can use xsd.exe tool to generate C# and VB.Net class from Google Checkout XSD file APIV@.xsd. now I will show you how you will use the generated class in your project to generate XML file that defines showing cart.

If you will use the generated .Net class in your project, generation of cart xml structure is no more than couple of lines of codes after you have filled required fields in apiv2 class members. For example if you have one item to add to shopping cart, the process is as follows:

• Create new CheckoutShoppingCart object.
• Then create ShoppingCart object in CheckoutShoppingCart object.
• Create Item object and fill the required fields itemname, itemdescription etc.
• Use XmlSerializer to serialize CheckoutShoppingCart to generate xml cart xml structure.

Following code snippets are fom a component library that we are developing to make use of Google Checkout API little easy to use.

protected void OnCheckOut(object sender, ImageClickEventArgs e)
{
    GCheckOutFlow checkoutFlow = new GCheckOutFlow("mymerchantid", "mymerchantkey");
    GCheckoutShoppingCart gCart = checkoutFlow.CreateShoppingCart();
    Google.CheckoutShoppingCart obShoopingCart = gCart.ShoopingCart;
    // Add items to the cart.
    Google.Item[] collItems = new Google.Item[1];
    Google.Item item = new Google.Item();
    item.itemname = "My Test Item";
    item.itemdescription = "My test item sold on google";
    item.quantity = Int32.Parse(ctlQtyTextBox.Text);
    Google.Money price = new Google.Money();
    price.currency = "USD";
    price.Value = 9.99M;
    item.unitprice = price;
    collItems[0] = item;
    obShoopingCart.shoppingcart.items  = collItems;
    obShoopingCart.checkoutflowsupport.Item = new Google.MerchantCheckoutFlowSupport();
    checkoutFlow.PlaceOrder(gCart);
}

public void PlaceOrder(GCheckoutShoppingCart oShoppingCart)
{
    if (null == oShoppingCart)
    {
        throw new ArgumentNullException("GCheckoutShoppingCart");
    }
    CheckoutProtocol oProtocol = new CheckoutProtocol(oShoppingCart);
    String strCartXml = oProtocol.SerializeCartToXml();
    System.Diagnostics.Debug.WriteLine(strCartXml);
    String strCartSigntaure = oProtocol.CreateCartSignature(strCartXml);
    String strEncodedCart = oProtocol.EncodeCart(strCartXml);
}

internal String SerializeCartToXml()
{
    StringBuilder strXml = new StringBuilder();
    XmlSerializer serializer = new XmlSerializer(typeof(Google.CheckoutShoppingCart));
    StringWriter sw = new StringWriter(strXml);
    serializer.Serialize(sw, m_oCart);
    sw.Close();
    return CleanupCartXml(strXml.ToString());
}
							

SerializeCartToXml demonstrates how serialization converts the object to xml document defining the xml structure as per XSD file.