JQuery Ajax 500 Internal Error

Question

I'm just starting to use the JQuery library so bear with me if I am missing something obvious. I have a webserivce with a couple of test methods...

[WebService(Namespace = "http://localhost/WebServices")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
// To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line. 
[System.Web.Script.Services.ScriptService]
public class SystemServices : BaseWebService
{
    [WebMethod(EnableSession = true)]
    public string GetDate()
    {
        return DateTime.Today.ToShortDateString();
    }
    [WebMethod(EnableSession = true)]
    public string PerformPISearch(string firstName, string lastName )
    {
        return firstName + lastName;
    }

I can use the $.ajax request to use the GetDate method which does not have parameters with no issue, but I get the 500 Internal Server Error returned from jQuery when I try to run the PerformPISearch method (the web service constructor never gets hit)...So I am assuming I am doing something wrong with the way I am trying to pass the paramters to the method, but I can't figure out what...

     function PerformSearch() {
     var strFirstName = (txtFirstName.GetValue() == null ? "" : txtFirstName.GetValue());
     var strLastName = (txtLastName.GetValue() == null ? "" : txtLastName.GetValue());
     var webserviceURL = '<%= WebServiceURL %>'

     $.ajax({
         type: "POST",
         url: webserviceURL + "SystemServices.asmx/PerformPISearch", //Can change to use GetDate and it works.
         data: ({firstName: strFirstName, lastName: strLastName}), //thinking the problem is here
         contentType: "application/json; charset=utf-8",
         dataType: "json",
         success: function(msg) {
             AjaxSucceeded(msg);
         },
         error: AjaxFailed
     });
 }

 function AjaxSucceeded(result) {
     alert(result.d);
 }
 function AjaxFailed(result) {
     alert(result.status + ' ' + result.statusText);
 }

Answer 1

Have you tried removing the "()" :

data: {firstName: strFirstName, lastName: strLastName}

or putting everything into a string :

data: "{'firstName': '" +strFirstName + "', 'lastName': '" +strLastName+ "'}"