Commerce server 2009-How to get the lineitems from the basket

The following is one way to retreive, there are some other methods using WebService, Orders Runtime, or CS2009 API calls (used in order details web part) .

I recommend to post in Commerce Server forums http://social.msdn.microsoft.com/Forums/en-US/commserver2009/threads

OrderSiteAgent ordersAgent = new OrderSiteAgent("Your Site Name");
 
            OrderManagementContext context = OrderManagementContext.Create(ordersAgent);
            PurchaseOrderManager manager = context.PurchaseOrderManager;

            DataSet searchableProperties = context.PurchaseOrderManager.GetSearchableProperties("en-US");

            SearchClauseFactory factory = context.PurchaseOrderManager.GetSearchClauseFactory(searchableProperties, "PurchaseOrder");
            SearchClause searchClause = factory.CreateClause(ExplicitComparisonOperator.Equal, "TrackingNumber", "122233");  //your search clause

            Microsoft.CommerceServer.SearchOptions options = new Microsoft.CommerceServer.SearchOptions();

            DataSet ds = context.PurchaseOrderManager.SearchPurchaseOrders(searchClause);
            DataSet ds1 = context.PurchaseOrderManager.GetPurchaseOrderAsDataSet(new Guid(ds.Tables[0].Rows[0][0].ToString()));
            DataTable dtLineItems = ds1.Tables["LineItems"];