Introducing WF4.0: Building Distributed Apps with WF 4.0 and WF 4.0 Services

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Activities;

namespace CustomActivities
{
    public class BookCar : CodeActivity
    {
        InArgument<string> carId;
        public InArgument<string> CarId
        {
            get { return carId; }
            set { carId = value; }
        }

        protected override void Execute(CodeActivityContext context)
        {
            string carId = CarId.Get(context);

            String urlstr = "http://mhalabi/CarRentalDataService/CarRentalService.svc";
            CarRentalReference.CarStoreEntities proxy = new CarRentalReference.CarStoreEntities(new Uri(urlstr));

            var query = (from c in proxy.Cars
                         where c.CarId == carId
                         select c);

            foreach (CarRentalReference.Car car in query)
            {
                car.Quantity = car.Quantity - 1;
                proxy.UpdateObject(car);
                proxy.SaveChanges();
                break;
            }
            
        }


    }
}