如何使用LINQ检索子集合

Starting here:

public class Customer
{
  public int CustomerID { get; set; }
  public string CustomerName { get; set; }  
  public IList<Order> Orders { get; set; }
}

public class Order
{
  public int OrderID { get; set; }
  public int CustomerID { get; set; }
}
public class Customer
{
  publ