通过LINQ to XML生成 XML
XML常常用语在客户机和服务器之间交流数据，或者多层应用程序之间交流。
用LINQ to SQL查询数据，再用LINQ to XML吧数据转换为XML.
例：
.......
AreslabDataContext aresData = new aresData(); //创建DataContext实例
XElement aresCustomerOrders = new XElement("customers", //创建XML片段实例
from c in aresData.Customers //利用LINQ查询数据，DataContext对象的Customers成员作为数据源
select new XElement("customer", //构建select投射
new XAtrribute("ID", c.CustomerID),
new XAtrribute("Company", c.CompanyName),
from o in c.orders
select new XElement("order",
new XAtrribute("orderID",o,OrderID),
new XAtrribute("orderTotal", o.Order_Detail.Sum(od=>od.Quantity*od.UnitPrice))
) //end order
) //end customer
); //end customers
string xmlFileName = "c:/.../aresCustomerOrders.xml";
aresCustomerOrders.Save(xmlFileName);