jQuery Grid Plugin - jqGrid

Hello,

I am using below Ajax call to get data for drop down.  I am not able to return data in the format which dropdowns want

{ '1': 'USA', '2': 'England' }

// Ajax call

 $.ajax({
                async: false,
                contentType: "application/json; charset=utf-8",
                url: url,
                dataType: "json",
                success: function (data)
                {
                      countries =eval( data);// data.d;//(data);
                 },
                 error: function (XMLHttpRequest, textStatus, errorThrown)
                {                           

                      alert("Error in function, countries: " + XMLHttpRequest.status + "\r\n" + textStatus + "\r\n" + errorThrown);
                }
          });

//ServerSide code

 public object  GetCountries()
        {
            var data = "";
            List<testData> lstData = new List<testData>();
            lstData.Add(new testData { Id = "1", country = "USA" });
            lstData.Add(new testData { Id = "2", country = "England" });
            for (int i = 0; i < lstData.Count; i++)
            {

               data = data  +"'" +lstData[i].Id + "'" + ":'" + lstData[i].country+"'" ;
                if (i != lstData.Count - 1)
                    data = data + ',';

            }
           data = "{" + data + "}";
         
         return data;

        }
Above code returns as "{ '1': 'USA', '2': 'England' }" which is string and not an object.  How   do I convert "{ '1': 'USA', '2': 'England' }" to { '1': 'USA', '2': 'England' } on client side?