[WebMethod(EnableSession = true)]
        public int NumberOfClicks()
        {
            if (HttpContext.Current.Session["Id"] != null)
                HttpContext.Current.Session["Id"] = (int)HttpContext.Current.Session["Id"] + 1;
            else
                HttpContext.Current.Session["Id"] = 1;

            return (int)HttpContext.Current.Session["Id"];
        }

public Form1()
        {
            InitializeComponent();

            _ser = new WindowsFormCountClicks.CountClicksWebReference.Service1();
            _ser.CookieContainer = new System.Net.CookieContainer();
        }


        CountClicksWebReference.Service1 _ser;

        private void button1_Click(object sender, EventArgs e)
        {            
            textBox1.Text = _ser.NumberOfClicks().ToString();
        }

 protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            _ser = new CountsClickWebReference.Service1();
            _ser.CookieContainer = new System.Net.CookieContainer();
            _cookies = new System.Net.CookieContainer();
            _ser.CookieContainer = _cookies;
            
            ViewState["ser"] = _ser;
        }
    }

    System.Net.CookieContainer _cookies;
    CountsClickWebReference.Service1 _ser;

protected void ASPxButton1_Click(object sender, EventArgs e)
    {       
        int res = ((CountsClickWebReference.Service1)ViewState["ser"]).NumberOfClicks();   
        ASPxTextBox1.Text = res.ToString();
    }