Knockoutjs data bind hidden field value

Question

I have a hidden field in a knockout template that updates its value using jquery. The problem is that when I try to pass this value to the server using ajax, I get a zero value in the controller. But the html source code shows that the value of the hidden field is being updated. If I replaced the hidden field with a text field, this will work fine only when entering text manually.

JQuery

        function getFileDetail(fileID, fileName) {
        $('#hdnFileName' + fileID).val(fileName);
        $('#lblFileName' + fileID).text(fileName);
    }

Here is the html knockout template:

    <script type="text/html" id="fileTemplate">
        <div data-role="fieldcontain">
            <a href="#" data-bind="click: function () { openFileUpload('file', ID) }"><label data-bind="text: 'File Upload ' + ID, attr: { id: 'lblFileName' + ID }"></label></a><input type="button" value="Remove" data-bind="click: removeFile" /> 
        </div>
        <input type="hidden" name="hdnFileName" data-bind="attr: { id: 'hdnFileName' + ID, value: fileName }" />
    </script>

ViewModel

function FileViewModel() {
        var self = this;
        self.ID = ko.observable();
        self.fileName = ko.observable();
        self.removeFile = function (file) { };
        self.Files = ko.observableArray([{ ID: 1, fileName: "", removeFile: function (file) { self.Files.remove(file); }}]);

        self.addNewFile = function () {
            var newFile = new FileViewModel();
            newFile.ID = self.Files().length + 1;
            newFile.fileName = "";
            newFile.removeFile = function (file) { self.Files.remove(file); };
            self.Files.push(newFile);
            //$("input[name='hdnFileName'").trigger("change");
        }
    }
function ViewModel() {
        var self = this;
        self.fileViewModel = new FileViewModel();
        self.submitForm = function () {

            $.ajax({
                type: "POST",
                url: "<%= Url.Action("MeetingPresenter")%>",
                data: "{Files:" + ko.utils.stringifyJson(self.fileViewModel.Files) + "}",
                contentType: "application/json",
                success: function (data) {},
            });
        };
    }

Answer 1

If you use knockout.js, you do not need to change the DOM, you can just update ViewModel, and the DOM will update according to

function getFileDetail(fileID, fileName) {
    viewModel.fileViewModel.update(fileID, fileName);
}

Add function updatetoFileViewModel

function FileViewModel() {
    // rest of the code

    self.update = function(fileID, fileName) {
        var file = ko.utils.arrayFirst(self.Files(), function(file) {
            return file.ID == fileID;
        });

        file.fileName(fileName); // this will change and the UI will be updated according
    };
}

. , Files, update, observable

self.Files = ko.observableArray([{ ID: 1, fileName: "", removeFile: function (file) { self.Files.remove(file); }}]);

, observable (.. ID: observable(1)), new FileViewModel().

: ViewModel ( ), undefined.

Answer 2

ID , "", , :

<input type="hidden" name="hdnFileName" data-bind="attr: { id: 'hdnFileName' + ID(), value: fileName }" />

:

<label data-bind="text: 'File Upload ' + ID(), attr: { id: 'lblFileName' + ID() }"></label>

Answer 3

, DOM . .value, . .

I wrote a small script to demonstrate. Every 2 seconds, it sets an input value through the DOM, but the observed boundary changes only when you enter something.

http://jsfiddle.net/qcv01h2e/

var viewModel = (function () {
    return {
        fv: ko.observable().extend({notify:'always'})
    };
}());

ko.applyBindings(viewModel);
setInterval(function () {
    console.debug("Set it");
    var f = document.getElementById('field');
    f.value = "Hi";
    console.debug("fv is", viewModel.fv());
}, 2000);

Answer 4

I ran into a similar problem when I need to set a value without user input. Before performing the click update function, I do the required model update. If you have mode operations, it is best to introduce a function into the model.

<input data-bind="click: function(){ isEnabled(true); update() }" />

What did I actually do

<input data-bind="click: function(){ isEnabled(!isEnabled()); update() }" />

Keep in mind that the asynchronous nature of javascript is.