ajax not sending json data to webmethod

I am doing simple save operation (Code is as per tutorial)
...but ajax is not sending json data to save method

on Firebug console it displays following Error:

"NetworkError: 500 Internal Server Error - http://localhost/WebApplication2/WebForm1.aspx/saveData"

(Note: My libraries are updated and properly placed.)

ajax

    var name = "neeraj";
    var gender = "male";

    $.ajax({
        type: "POST",
        url: "WebForm1.aspx/saveData",
        data: { 'name': JSON.stringify(name), 'Gender': JSON.stringify(gender) },
        contentType: "application/json;charset=utf-8",
        dataType: "JSON",
        async: "true",
        success: function (response) {
            alert('success');
        }
    });

My page url is

  ../WebApplication2/WebForm1.aspx

save method(webform1.aspx.cs)

[WebMethod]
[ScriptMethod(ResponseFormat = ResponseFormat.Json)]
public static int saveData(string name, string Gender) 
{ return 1;}

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