I'm using ajax call in ASP.NET application and I'm getting entire HTML page as response from jquery Ajax call

Question

I'm developing an ASP.NET web application. Where in login screen I used jQuery Ajax call to connect server side code. In the response from the ajax call Im getting entire HTML page instead of true or false ( the actual result I want from the response).

Below is my server code.

[WebMethod]
    public static string LoginValidation(string userName, string passWord)
    {
        string connectionString = ConfigurationManager.ConnectionStrings["DBConnectionString"].ConnectionString;
        SqlConnection con = new SqlConnection(connectionString);
        SqlCommand cmd = new SqlCommand("select * from LoginUser where username = '"
            + userName + "' and password = '" + passWord + "'");
        SqlDataReader rdr = cmd.ExecuteReader();
        if (rdr.HasRows)
        {
            return "succes";
        }
        return "failure";
    }        

Below is my Jquery Ajax call.

 $(document).ready(function () {
    $('#txtLogin').focus();
});

$('#btnLogin').click(function () {
    var username = $('#txtLogin').val();
    var password = $('#txtPassword').val();

    if (username === "" || password === "") {
        alert('Both the fields are mandatory. Kindly try again');
        $('#txtLogin').focus();
        return;
    }
    else {
        //ajax call to validate the login
        $.ajax({
            type: 'POST',
            data: { 'userName': username, 'passWord': password },
            url: 'Default.aspx/LoginValidation',
            async: true,
            datatype: 'text',
            success: function (data) {
            alert('test sadfadfa '+data+' '+data.responseText);
                if (data == "failure") {
                    //redirecting to master page once after the successfull login
                    window.location.href = "/masterscreen.aspx";
                }
                else {
                    alert('false');
                }
                return;
            },
            error: function (data) {

            }
        });
        //ajax call end
    }
});

Answer 1

i've included the contentType in my Ajax call. It resolved my problem. Now, I'm getting JSON response as expected. Hope this helps some one.Thanks for those who helped me out.