Unknown web method GetBankNames.

Question

Web Service

namespace WebApp1.Services
{
    /// <summary>
    /// Summary description for WebAppService
    /// </summary>
    [WebService(Namespace = "http://localhost/")]
    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
    [System.ComponentModel.ToolboxItem(false)]
    // To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line.
    [ScriptService]
    public class WebAppService : WebService
    {
        [WebMethod]
        [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
        public static List<string> GetBankNames(string pre)
        {
            List<string> listBanks = new List<string>();
            DataTable dtData = new DataTable();
            string conString = ConfigurationManager.ConnectionStrings["dbConnection"].ConnectionString;
            SqlConnection sqlCon = new SqlConnection(conString);
            sqlCon.Open();
            SqlCommand sqlCmd = new SqlCommand("Select BankId, BankName From BankMaster Where BankName Like '%' + @SearchText + '%'", sqlCon);
            sqlCmd.Parameters.AddWithValue("@SearchText", pre);
            SqlDataAdapter sqlDa = new SqlDataAdapter(sqlCmd);
            sqlDa.Fill(dtData);
            sqlCon.Close();
            if (dtData.Rows.Count > 0)
            {
                for (int i = 0; i < dtData.Rows.Count; i++)
                {
                    listBanks.Add(string.Format("{0}-{1}", dtData.Rows[i]["BankName"], dtData.Rows[i]["BankId"]));
                }
            }
            return listBanks;
        }
    }
}

 Script

<script type="text/javascript">
    $(function () {
        $('#<%=txtAutoComplete.ClientID%>').autocomplete({
            minLength: 1,
            source: function (request, response) {
                $.ajax({
                    url: "Services/WebAppService.asmx/GetBankNames",
                    data: "{ 'pre':'" + request.term + "'}",
                    dataType: "json",
                    type: "POST",
                    contentType: "application/json; charset=utf-8",
                    success: function (data) {
                        response($.map(data.d, function (item) {
                            return {
                                label: item.split('-')[0],
                                val: item.split('-')[1]
                            }
                        }))
                    },
                    error: function (response) {
                        alert(response.responseText);
                    },
                    failure: function (response) {
                        alert(response.responseText);
                    }
                });
            },
            select: function (e, i) {
                $("[id$=hfBankId]").val(i.item.val);
            },
        });
    });
</script>

 When ever i call the web service always get error as "Unknown web method GetBankNames".