Urgent...AutoComplete Extender not working

<asp:AutoCompleteExtender ID="TextBox1_AutoCompleteExtender" runat="server" CompletionInterval="0"
                    CompletionListElementID="search" CompletionSetCount="12" EnableCaching="true"
                    MinimumPrefixLength="1" ServiceMethod="GetEmpID" ServicePath="~/WebService1.asmx"
                    ShowOnlyCurrentWordInCompletionListItem="true" TargetControlID="TextBox1" >
            </asp:AutoCompleteExtender> 

[System.Web.Services.WebMethod]
        [System.Web.Script.Services.ScriptMethod]
        public string[] GetEmpID(string prefixText)
        {
            SqlConnection con = new SqlConnection("server=sushma-pc;user id=sa;password=secure2011;database=dbase");
            DataSet ds = new DataSet();
            DataTable dt = new DataTable();
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con;
            cmd.CommandType = CommandType.Text;
            cmd.CommandText = "select Distinct EmpID from Tbl_EmpDetails where EmpID like @myParameter";
            cmd.Parameters.AddWithValue("@myParameter", "%" + prefixText + "%");

            try
            {
                con.Open();
                cmd.ExecuteNonQuery();
                SqlDataAdapter da = new SqlDataAdapter(cmd);
                da.Fill(ds);
            }
            catch
            {
            }
            finally
            {
                con.Close();
            }
            dt = ds.Tables[0];

            List<string> EmpID = new List<string>();
            String dbValues;

            foreach (DataRow row in dt.Rows)
            {

                dbValues = row["EmpID"].ToString();
                dbValues = dbValues.ToLower();
                EmpID.Add(dbValues);
            }

            return EmpID.ToArray();
        }
    }