ObjectQuery<T>.Include Method

// Create a SalesOrderHeader query with two query paths,  
// one that returns order items and a second that returns the  
// billing and shipping addresses for each order.
ObjectQuery<SalesOrderHeader> query =
    context.SalesOrderHeaders.Include("SalesOrderDetails").Include("Address");

using (AdventureWorksEntities context =
    new AdventureWorksEntities())
{
    // Define an object query with a path that returns  
    // orders and items for a specific contact.
    Contact contact =
        context.Contacts.Include("SalesOrderHeaders.SalesOrderDetails")
        .FirstOrDefault();

    // Execute the query and display information for each item  
    // in the orders that belong to the first contact. 
    foreach (SalesOrderHeader order in contact
        .SalesOrderHeaders)
    {
        Console.WriteLine(String.Format("PO Number: {0}",
            order.PurchaseOrderNumber));
        Console.WriteLine(String.Format("Order Date: {0}",
            order.OrderDate.ToString()));
        Console.WriteLine("Order items:");
        foreach (SalesOrderDetail item in order.SalesOrderDetails)
        {
            Console.WriteLine(String.Format("Product: {0} "
                + "Quantity: {1}", item.ProductID.ToString(),
                item.OrderQty.ToString()));
        }
    }
}