autocomplete extender how does it work

Question

i have have taken project name and project code in a autocomplete textbox the code is given below when i type name it comes with respective code , i want to know how what is assigned in that textbox name or code because i want to give further function for code only

 

[System.Web.Script.Services.ScriptMethod()]
        [System.Web.Services.WebMethod]

        public static List<string> GetSearch(string prefixText)
        {

            DataTable dt = new DataTable();
            SqlConnection con = new SqlConnection(con_Vas);
            SqlCommand cmd = new SqlCommand("SELECT [Employee Name]+';     '+[Employee Code] as Name FROM [HRPLK].[dbo].[View_EmployeeBasicInformation] where [Employee Name] like '%'+ @EmpName +'%' ");
            cmd.Parameters.AddWithValue("@EmpName", prefixText);
            cmd.Connection = con;
            con.Open();
            List<string> employees = new List<string>();
            using (SqlDataReader sdr = cmd.ExecuteReader())
            {
                while (sdr.Read())
                {
                    employees.Add(sdr["Employee Code"].ToString());

                }
            }


            con.Close();

            return employees;


        }