c# - Knockout not populating DateTime? when initial is null -

i'm using knockout bind view model view. multiple properties in view model nullable, such datetime?s. here's example:

public class viewmodel {     public int id { get; set; }     public string name { get; set; }     public datetime? creationdate { get; set;} } 

as can see, property creationdate nullable datetime.

i'm binding property custom datepicker binder:

ko.bindinghandlers.datepicker = {     init: function (element, valueaccessor, allbindingsaccessor, viewmodel) {         try {             var jsondate = ko.utils.unwrapobservable(valueaccessor());             var value = parsejsondatestring(jsondate);             var strdate = value.getmonth() + 1 + "/"                             + value.getdate() + "/"                             + value.getfullyear();             element.setattribute('value', strdate);         }         catch (exc) {         }         $(element).change(function () {             var value = valueaccessor();             value(element.getattribute('value'));         });     },     update: function (element, valueaccessor, allbindingsaccessor, viewmodel) {         var val = valueaccessor();         val(element.getattribute('value'));     } };  var jsondatere = /^\/date\((-?\d+)(\+|-)?(\d+)?\)\/$/; var parsejsondatestring = function (value) {     var arr = value && jsondatere.exec(value);     if (arr) {         return new date(parseint(arr[1]));     }     return value; }; 

this enables me bind property in view so:

<input type="text" data-bind="datepicker: creationdate" /> 

problem

here's problem. property null when enters view. json example this:

{   "id": 2004,   "name": "test",   "creationdate": null } 

if case, , change value random value datepicker, , send ajax post controller, can see models creationdate still equal null.

so if datetime null model enters view, how populate models property?

found solution on own

i managed solve issue changing binding following:

ko.bindinghandlers.datepicker = {     init: function (element, valueaccessor, allbindingsaccessor) {         //initialize datepicker optional options         var options = allbindingsaccessor().datepickeroptions || {};         $(element).datepicker(options);          //handle field changing         ko.utils.registereventhandler(element, "change", function () {             var observable = valueaccessor();             var value = $(element).val();             // if input field empty, value falsy , therefore observable should = null             if(!value){                 observable(null);             } else {                 var date = new date(value);                 observable(date);             }         });          //handle disposal (if ko removes template binding)         ko.utils.domnodedisposal.adddisposecallback(element, function () {             $(element).datepicker("destroy");         });      },     //update control when view model changes     update: function (element, valueaccessor) {         var value = ko.unwrap(valueaccessor());         //if value received null, should display nothing in input field         if (value === null) {             $(element).val(null);         } else {             //we need manipulate data show user friendly user             var date = parsejsondatestring(value);             var strdate = date.getmonth() + 1 + "/"                                         + date.getdate() + "/"                                         + date.getfullyear();             $(element).val(strdate);         }     } }; 

so if value i'm getting in update function, set $(element).val(null). way, nullable properties handled correctly.