Ajax AutoCompleteExtender in ASP.NET

<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<asp:AutoCompleteExtender ID="AutoCompleteExtender1" runat="server"
      TargetControlID="TextBox1" ServiceMethod="GetCompletionList"
      ServicePath="AjaxLearning.asmx" MinimumPrefixLength="1"
      ShowOnlyCurrentWordInCompletionListItem="True">
</asp:AutoCompleteExtender>

Using Service File Method : (.asmx)


    [WebMethod]
    public string[] GetCompletionList(string prefixText)
    {
     
        SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["mystring"].ConnectionString);
        SqlCommand com = new SqlCommand("SELECT Username FROM Table_Login WHERE Username LIKE '" + prefixText + "%'", conn);
        com.CommandType = CommandType.Text;
        conn.Open();
        SqlDataReader reader = com.ExecuteReader();


        List<string> strarr = new List<string>();


        while (reader.Read())
        {
            strarr.Add(reader.GetString(0));
        }


        conn.Close();
        return strarr.ToArray();

    }


Using Handler : (.ashx)



public class AutocompleteData : IHttpHandler {
 
    public void ProcessRequest (HttpContext context) {
        string firstname = context.Request.QueryString["q"];
        string sql = "select top 10 Username from Table_Login where Username like '" + firstname + "%'";

        using (SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["mystring"].ConnectionString))
        using (SqlCommand command = new SqlCommand(sql, connection))
        {
            connection.Open();

            using (SqlDataReader reader = command.ExecuteReader())
            {
                while (reader.Read())
                {
                    context.Response.Write(reader.GetString(0) + Environment.NewLine);
                }
            }
        }
    }

    public bool IsReusable {
        get {
            return false;
        }
    }

}