Problem LineChart

Hello,

I would like to display a Line Chart depending of the DropDownList control.

When I choose a value of this DropDown, the Line Chart display with the average of my value column group by the value of my DropDown.

This is my code behind :

 protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                string query = "select distinct Entite from reponse";
                DataTable dt = GetData(query);
                NomEntite.DataSource = dt;
                NomEntite.DataTextField = "Entite";
                NomEntite.DataValueField = "Entite";
                NomEntite.DataBind();
                NomEntite.Items.Insert(0, new ListItem("Selectionnez", ""));
            }
        }

        protected void entite_SelectedIndexChanged(object sender, EventArgs e)
        {
            string query = string.Format("select Entite, AVG(AvancementQuantitatifT1 * 100) FROM reponse WHERE Entite = '{0}' GROUP BY Entite", NomEntite.SelectedItem.Value);
            DataTable dt = GetData(query);

            string[] x = new string[dt.Rows.Count];
            decimal[] y = new decimal[dt.Rows.Count];
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                x[i] = dt.Rows[i][0].ToString();
                y[i] = Convert.ToInt32(dt.Rows[i][1]);
            }
            LineChart1.Series.Add(new AjaxControlToolkit.LineChartSeries { Data = y });
            LineChart1.CategoriesAxis = string.Join(",", x);
            LineChart1.ChartTitle = string.Format("{0}", NomEntite.SelectedItem.Value);
            if (x.Length > 3)
            {
                LineChart1.ChartWidth = (x.Length * 75).ToString();
            }
            LineChart1.Visible = true;
        }

        private static DataTable GetData(string query)
        {
            DataTable dt = new DataTable();
            string constr = ConfigurationManager.ConnectionStrings["connexionBase"].ConnectionString;
            using (SqlConnection con = new SqlConnection(constr))
            {
                using (SqlCommand cmd = new SqlCommand(query))
                {
                    using (SqlDataAdapter sda = new SqlDataAdapter())
                    {
                        cmd.CommandType = CommandType.Text;
                        cmd.Connection = con;
                        sda.SelectCommand = cmd;
                        sda.Fill(dt);
                    }
                }
                return dt;
            }
        }

The column Entite is a Varchar type and AvancementQuantitatifT1 is a decimal (3,2) type.

Nothing display when I choose a value of my DropDownList.