InputBox autocomplete in asp classic

<asp:TextBox ID="txt1" runat="server"></asp:TextBox>
        <ajaxToolkit:AutoCompleteExtender ID="autoExtender" runat="server" TargetControlID="txt1" ServiceMethod="GetEmpNames" 
            MinimumPrefixLength="1" CompletionInterval="100" EnableCaching="false" CompletionSetCount="10"></ajaxToolkit:AutoCompleteExtender>

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

    [System.Web.Services.WebMethod]

    public static List GetEmpNames(string prefixText)
    {
        SqlConnection con = new SqlConnection("DataBase=ENGSOFT;User id=sa;Password=P@ssword9");
        con.Open();
        SqlCommand cmd = new SqlCommand("select empno, ename,job,mgr,hiredate,sal,comm,picture from emp where ename like '%'+ @Name+'%'", con);
        cmd.Parameters.AddWithValue("@Name", prefixText);
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        DataTable dt = new DataTable();
        da.Fill(dt);

        List Empname = new List();

        for (int i = 0; i < dt.Rows.Count; i++)
        {
            Empname.Add(dt.Rows[i]["ename"].ToString());
        }
        con.Close();
        return Empname;
    }