c# - Jquery $.ajax, msg is empty when I call a web service (WCF) method -

i have web service wcf , call methods of wcf jquery ajax.

when tested method without parameter, works well.

but when call method parameter, doesn't work.

the problem in success in $.ajax, msg empty.

here javascript code :

function getstatistic3() {  var response; var allstat3 = []; var allyearstat3 = [];  var kla = $('#select1').val(); kla = kla.replace("'", "\\'"); if (kla) {     $.ajax({         type: 'get',         url: 'http://localhost:52768/service1/statistic_3',         data: "klant='" + encodeuricomponent(kla) + "'",         contenttype: 'application/json; charset=utf-8',         datatype: 'json',         success: function (msg) {             response = msg;             (var = 0; < response.items.length; i++) {                 var j = 0;                 allstat3[i] = [response.items[i].interventie, response.items[i].sum[j], response.items[i].sum[++j], response.items[i].sum[++j], response.items[i].sum[++j], response.items[i].sum[++j]];             }             allyearstat3[0] = [response.items[0].yearstart, response.items[0].yearstart + 1, response.items[0].yearstart + 2, response.items[0].yearstart + 3, response.items[0].yearstart + 4];             filldatatable3(allstat3, allyearstat3);             if (bool3) {                 $('thead tr th:eq(0)').replacewith(function () {                     return $("<td />").append($(this).contents());                 });                 $('thead th').attr('scope', 'col');                 bool3 = false;             }             $('table').visualize({ type: 'line' });         },         error: function (e) {             alert("error loading statistic 3");         }     }); } } 

i tested .asmx web service , works well.

i have error when call method :

typeerror: response.items[0] undefined 

msg empty :

i think have problem when pass parameter in ma $.ajax.