Building web services with persistent state

using System;
using System.Web;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;
using System.Runtime.Serialization;

[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
public class Service : System.Web.Services.WebService
{
    public Service()
    {

        //Uncomment the following line if using designed components 
        //InitializeComponent(); 
    }

    [WebMethod]
    public string MethodCall_ver2(int id)
    {
        //We have a setting in web.config which tells us where should we store the files. 
        // The setting is called TemporaryDirectory

        //Check to see if the file if the specified directory exists. If it does, this is not the first request and we retrieve it
        if (File.Exists(string.Format("{0}{1}.dat", System.Configuration.ConfigurationManager.AppSettings["TemporaryDirectory"],   id )))
        {
            //Get a FileStream to point to that file
            FileStream sr = new FileStream(string.Format("{0}{1}.dat", System.Configuration.ConfigurationManager.AppSettings["TemporaryDirectory"], id), FileMode.Open);
            //Create an object used in serializing/deserializing objects
            BinaryFormatter bf = new BinaryFormatter();
            //deserialize the object
            d = (UserDefinedClass)bf.Deserialize(sr);
            sr.Close();
        }
        else
        {
            //if the file does not exist then we create a new object
            d = new UserDefinedClass();
        }

        //Call methods on the object

        //We serialize the object back to the file system
        FileStream sw = new FileStream(string.Format("{0}{1}.dat", System.Configuration.ConfigurationManager.AppSettings["TemporaryDirectory"], id), FileMode.OpenOrCreate);

        BinaryFormatter abf = new BinaryFormatter();
        abf.Serialize(sw, d);
        sw.Close();

        //The service returns
        return string.Format("{0}", d.something.ToString());
    }


    [WebMethod]
    public string MethodCall_ver1(int token)
    {
        UserDefinedClass d = null;

        //If the token not found in the Application object, we retrieve it
        if (Application[token.ToString()] != null)
        {
            d = (UserDefinedClass)Application[token.ToString()];
        }
        else
        {
            //if the token was not found then we create a new object
            d = new UserDefinedClass();
        }

        //Call methods on the object

        //We save the object into the Application object
        Application[token.ToString()] = d;

        //The service returns
        return string.Format("{0}", d.something.ToString());
    }

}
[Serializable]
public class UserDefinedClass
{
    public UserDefinedClass()
    {
        something = 0;
    }

    public int something;
}