ASP.net PageMethods return undefined

Question 1

You need to supply a success and a failure callback to the webmethod call as below.

  $(window).load(function () {
                                    PageMethods.isConnected(fnsuccesscallback,fnerrorcallback);

        });
        function fnsuccesscallback(data) {
            alert(data);

        }
        function fnerrorcallback(result) {
            alert(result.statusText);
        }

Also, there is another way of accessing the page methods using $.ajax.

<head id="Head1" runat="server">
    <title></title>
    <script src="../assets/lib/jquery/jquery-2.0.3.js" type="text/javascript"></script>
    <script src="Scripts/jquery-1.9.1.js" type="text/javascript"></script>
    <script type="text/javascript" language="javascript">

         $(window).load(function () {

      $.ajax({
            type: "POST",
            url: "PageMethodTest.aspx/isConnected",
            data: "{}",
            contentType: "application/json; charset=utf-8",
            dataType: "json",
            success: fnsuccesscallback,
            error:fnerrorcallback
        });
    });            function fnsuccesscallback(data) {
            alert(data.d);

        }
        function fnerrorcallback(result) {
            alert(result.statusText);
        }
    </script>
</head>
<body>
    <form id="form1" runat="server">
    <asp:ScriptManager EnablePageMethods="true" runat="server">
    </asp:ScriptManager>
    <div>
    </div>
    </form>
</body>

Question 2

Will do 100% work

     <script type="text/javascript">
       function Generate()
       {              
           var result = PageMethods.GenerateOTP(your parameter, function (response)
           {
               alert(response);
           });
       }
</script>