Remote Validation with Knockout in MVC 4, Allowing invalid data to save - asp.net-mvc

Question

Hi there I am using remote validation with knockout validation rules to check if a client is booked at the same time as the proposed date. I finally got the viewmodel sending data to the controller validation method and the method does return a true or false however i began to notice that the call back was not stopping the user from saving if the client is not valid.
I found this by swapping the conditions and allowing the controller method to return false I debugged the client side and found that the call back variable was in fact false but i was not receiving an error messae nor was it stopping m from saving the appointment.
My question is am i missing a piece of code that allows this or is there a bug that i am missing?
Viewmodel rule validation:
ko.validation.rules['validateClientasync'] = {
async: true,
message: 'Client is already booked in at this time!',
validator: function (val, parms, callback) {
var defaults = {
url: '/Appointments/CheckClient/',
type: 'POST',
contentType: 'application/x-www-form-urlencoded',
success: function (data) {
callback(/* true or false depending on what you get back in data */);
}
};
if (parms.data != undefined && parms.data.appointment != undefined) {
var appointment = ko.toJS(parms.data.appointment);
$.ajax({
url: '/Appointments/CheckClient/',
type: 'post',
contentType: 'application/x-www-form-urlencoded',
data: ko.toJS(parms.data.appointment),
success: function(data) {
callback(/* true or false depending on what you get back in data */);
}
});
}
}
};
ko.validation.registerExtenders();
self.appointment = {
id: appointment.id,
start: ko.observable(appointment.start),
end: ko.observable(appointment.end),
text: ko.observable(appointment.text),
clientid: ko.observable(appointment.clientid).extend({
validateClientasync: {
data: self
}
}),
employeeid: ko.observable(appointment.employeeid),
roomid: ko.observable(appointment.roomid),
fee: ko.observable(appointment.fee).extend({min: 10})
};

Answer 1

according to the definition in https://github.com/Knockout-Contrib/Knockout-Validation/wiki/Async-Rules, just put a json there would be enough, like:
callback(
{
isValid: true //true or false with json format returned from the validation method in your controller,
message: "your cusotm error message here"
}
);