ASP.NET

<connectionStrings>
        <add name="conn" connectionString="Data Source=.;Initial Catalog=Tranning;Integrated Security=True" providerName="System.Data.SqlClient"/>
        <add name="tempdbConn" connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\tempdb.mdf;Integrated Security=True;User Instance=True" providerName="System.Data.SqlClient"/>
    </connectionStrings>

[System.Web.Script.Services.ScriptMethod()]
        [System.Web.Services.WebMethod]
        public static List<string> SearchCustomers(string prefixText, int count)
        {
            using (SqlConnection conn = new SqlConnection())
            {
                conn.ConnectionString = ConfigurationManager
                        .ConnectionStrings["conn"].ConnectionString;
                using (SqlCommand cmd = new SqlCommand())
                {
                    //cmd.CommandText = "select ContactName from Customers where " +
                    //"ContactName like @SearchText + '%'";
                    cmd.CommandText = "select No_Trainee from Annual_Plan where No_Trainee like @SearchText + '%' ";
                    cmd.Parameters.AddWithValue("@SearchText", prefixText);
                    cmd.Connection = conn;
                    conn.Open();
                    List<string> customers = new List<string>();
                    using (SqlDataReader sdr = cmd.ExecuteReader())
                    {
                        while (sdr.Read())
                        {
                            customers.Add(sdr["No_Trainee"].ToString());
                        }
                    }
                    conn.Close();
                    return customers;
                }
            }
        }