Mascara Celular

Mascara Celular (9XXXX-XXXX)

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
    <script type="text/javascript" src="jquery-1.9.1.js"></script>
    <script src="jquery.maskedinput.js" type="text/javascript"></script>
    <script type="text/javascript">
         //Testando o jQuery
            $(document).ready(function() {
                alert("Olá Mundo");
        });

            function Mascara(campo) {

function trata(valor, isOnBlur) {

valor = valor.replace(/\D/g, "");
valor = valor.replace(/^(\d{2})(\d)/g, "($1)$2");

if (isOnBlur) {

valor = valor.replace(/(\d)(\d{4})$/, "$1-$2");
} else {

                        valor = valor.replace(/(\d)(\d{3})$/, "$1-$2");
                    }
                    return valor;
                }

campo.onkeypress = function (evt) {

var code = (window.event) ? window.event.keyCode : evt.which;
var valor = this.value

                    if (code > 57 || (code < 48 && code != 8)) {
                        return false;
                    } else {
                        this.value = trata(valor, false);
                    }
                }

campo.onblur = function () {

                    var valor = this.value;
                    if (valor.length < 13) {
                        this.value = ""
                    } else {
                        this.value = trata(this.value, true);
                    }
                }

                campo.maxLength = 14;
            }
</script>
</head>
<body>
    <form id="form1" runat="server">
       <asp:TextBox runat="server" ID="txtTelefone" MaxLength="14" onKeyDown="Mascara(this);"
      onKeyPress="Mascara(this);" onKeyUp="Mascara(this);" />