Можно попробовать
var id=1;
$.ajax({
type: 'post',
url: '../webservice.asmx/yourmethod',
contentType: "application/json; charset=utf-8",
data:{'id':id}
dataType: "json",
beforeSend: function () {
//show wait
},
success: function (msg) {
if (msg.d != null) {
//result is obtained
}
}
});