Develop Reference

How to resolve a not working cascading drop down

I have a cascading dropdown like for eg first dropdown shows the list of countries and based on the selection of countries the next dropdown gets populated. The problem is that in development environment it's working fine but when deployed in a server the first dropdown gets populated correctly as it's elements come from resource file and after selection of first drop down I get an error.
JS :
<script>
$(document).ready(function () {
$("#Site").change(function () {
var SelectedVal = $(this).val();
$("#Model").html('');
$("#Model").append($("<option></option>").attr("value", '')
.text(' '));
if (SelectedVal != '') {
$.get("/Home/GetModelList", { Sid: $("#Site").val() }, function (data) {
$("#Model").empty();
$("#Model").html('');
$("#Model").append($("<option></option>").attr("value", '')
.text(' '));
if (data.modelAlert != null) {
alert(data.projectAlert);
}
$.each(data.models, function (index, item) {
$("#Model").append($('<option></option>').text(item));
});
});
}
})
});
</script>
Controller :
public JsonResult GetModelList()
{
List<string> models = db.GetModels();
string modelAlert = alert.GetAlert();
var result = new { modelAlert, models };
return Json(result, JsonRequestBehavior.AllowGet);
}
The error message that I get is
Failed to load resource: the server responded with a status of 404 (Not Found) Home/GetModelList?Sid=Ind:1
I checked for similar problems like this and it was all about the JS path or the controller path but I've already given the absolute path. Can someone let me know where am I going wrong, let me know if any additional data is needed.
Thanks

$.get("/Home/GetModelList", { Sid: $("#Site").val() }, function (data) {
The above line was causing the routing problem, usually when we call a controller action from js in this way there tends to be a routing problem due to the folder structure reference. In order to avoid this routing problem and to be more clear we can also call controller action from js like below
$.get('#Url.Action("MethodName", "ControllerName")', function (data) {
This resolved my issue.

Downloading a file with Knockout bindings, ASP.NET MVC stack and no Razor

Trying to find a resource that could point me in the right direction for downloading a file with this particular stack. It's more challenging than it seems, especially since I'm unable to use Razor in accordance with house rules.
The code execution can get from the markup, to the knockout, and then the C#, but it doesn't start a download like I would expect in ordinary webforms non-MVC ASP.NET.
mark up:
<div class="row">
<div class="col-2"><img data-bind="attr: {src: image}, click: $root.downloadFile/></div>
the knockout/javascript call:
self.downloadFile = function(e){
if(e) {
attachmentId = e.id;
helpers.ajax.getJson(root, "/Files/DownloadFile/", {fileId: attachmentId }, function(x){
attachmentId=0;
getFiles();
});
}
...
related javascript functions called here:
helpers.ajax.getJson = function(path, url, data, onSuccess, onError){
helpers.ajax.async('GET', path, url, {
data: data,
cache: false,
async: true,
error: onError,
success: onSuccess
});
};
function getFiles(){
self.files([]);
helpers.ajax.getJson(root, "/Files/GetFiles",
{ profileId: self.ProfileId() },
function (files) {
if(files) {
$.each(files, function (i, v) {
self.files().push(new file(v.AttachmentId, v.FileTypeDescr, v.FileExtension, v.FileName, v.UploadedBy, v.UploadDate, v.CompletionDate));
self.files.valuehasMutated();
});
}
});
}
C#
public FileResult DownloadFile(int fileId)
{
ODSAPI.AttachmentFile file = FileFunctions.GetById(fileId);
if(file != null)
{
return File(file.FileData, file.ContentType);
}
return null;
}
this returns the correct file information and the bits from the database when I step through the code and view the file variable.

you could use http://danml.com/download.html to download file from javascript AJAX return
for exmaple
download(data, 'Export.csv', 'application/csv');
where data will be return from your ajax request and file name and file type.

The JSON call in the Javascript was incorrect as it called for a JSON object. Rather, it should have been:
window.open(root + "/Files/DownloadFile?fileId=" + attId, '_blank');
instead of helpers.ajax.getJson()

Calling a web service from Javascript (passing parameters and returning dataset)

I have created a web service in C# and now need to call it from a mobile app. I'm trying to create a Windows 7 mobile app, but using HTML5 and Javascript not the native code. The web service takes 2 parameters, Email and Password, and returns a Dataset. I don't really have any javascript experience (or web services experience for that matter, trying to learn with this project), and when trying to research how to call a web service using javascript I just found too much information and didn't know where to begin because so many other technologies were also mentioned.
So I decided to try things out and this is what I came up with so far:
<script type="text/javascript">
document.addEventListener("deviceready", onDeviceReady, false);
// once the device ready event fires, you can safely do your thing! -jm
function onDeviceReady() {
}
function LoginButton_onclick() {
UpdateChildrenApp.PhoneWebServices.GetMyChildren(document.getElementById('EmailBox').value,document.getElementById('PasswordBox').value, OnComplete, OnError)
}
function OnComplete(result) {
for (var i = 0; i < result.tables[0].rows.length; i++)
document.getElementById('Test').innerHTML += ''+(result.tables[0].rows[i].col_name);
}
function OnError(result) {
document.getElementById('Test').innerHTML ='Error :'+result.get_message();
}
</script>
This code does nothing when I press the submit button. Could someone please point out what the problems are and how I can fix them or suggest what I should research to address the problems and put me on the right track? Any help is greatly appreciated.

First, your webservices should return a JSON object if you want to use it in javascript.
You can of course return any XML/string, but using JSON will be A LOT easy to use the data in javascript.
Then, I would advise you to use jquery to call the webservice, as jquery will do a lot of work for you.
Read this article, it should help you set different components correctly:

I would use jQuery to do this kind of thing.
The ajax functionality its provides is really easy to use.
I would use the Revealing Module Pattern (RMP) and 2 javascript files. If you're unfamiliar with the RMP, there is a great post covering it here:
http://weblogs.asp.net/dwahlin/archive/2011/08/02/techniques-strategies-and-patterns-for-structuring-javascript-code-revealing-module-pattern.aspx
I find that if I dont employ some kind of structure to my js code using the RMP, I just end up with a mess of functions in one file.
Id have Startup.js and Dataservice.js and they would look something like this:
Startup.js
var Startup = function () {
var isValid,
dataObject = {},
populateDataObject = function () {
dataObject.dealer = $("[id$='_txtUser']").val();
dataObject.password = $("[id$='_txtPassword']").val();
},
init = function () {
var dealerId = 0;
$("[id$='_SubmitButton']").bind('click', function (evt) {
evt.preventDefault();
populateDataObject();
if (isValid) {
Dataservice.processLoginRequest(dataObject, processLoginRequestResult);
}
});
};
return {
init: init,
processLoginRequestResult: processLoginRequestResult
};
} ();
Dataservice.js (assumes old school .asmx, change as needed)
var Dataservice = function () {
$.ajaxSetup({
type: "POST",
contentType: "application/json; charset=utf-8",
dataType: "json"
});
var serviceBase = '../services/LoginService.asmx/',
processScreenRequest = function (valObject, callback) {
$.ajax({
url: serviceBase + "ProcessLoginRequest",
data: JSON.stringify(valObject),
success: function (json) {
callback(json);
}
});
};
return {
processScreenRequest: processScreenRequest
};
} ();
and then I would include refereces to these 2 js files as well as jquery in my html page.
I hope this helps.

I've used Dojo for this once, its pretty simple you can make xhrget or xhrpost requests. It has a function called load that is the callback where you can modify the contents of the HTML components in the page.
Use these links : http://dojotoolkit.org/reference-guide/1.7/dojo/xhrGet.html

Access a Model property in a javascript file?

Is it possible to access a Model property in an external Javascript file?
e.g. In "somescript.js" file
var currency = '#Model.Currency';
alert(currency);
On my View
<script src="../../Scripts/somescript.js" type="text/javascript">
This doesn't appear to work, however if I put the javascript directly into the view inside script tags then it does work? This means having to put the code in the page all the time instead of loading the external script file like this:
#model MyModel;
<script lang=, type=>
var currency = '#Model.Currency';
alert(currency);
</script>
Is there any way around this?

I tackled this problem using data attributes, along with jQuery. It makes for very readable code, and without the need of partial views or running static javascript through a ViewEngine. The JavaScript file is entirely static and will be cached normally.
Index.cshtml:
#model Namespace.ViewModels.HomeIndexViewModel
<h2>
Index
</h2>
#section scripts
{
<script id="Index.js" src="~/Path/To/Index.js"
data-action-url="#Url.Action("GridData")"
data-relative-url="#Url.Content("~/Content/Images/background.png")"
data-sort-by="#Model.SortBy
data-sort-order="#Model.SortOrder
data-page="#ViewData["Page"]"
data-rows="#ViewData["Rows"]"></script>
}
Index.js:
jQuery(document).ready(function ($) {
// import all the variables from the model
var $vars = $('#Index\\.js').data();
alert($vars.page);
alert($vars.actionUrl); // Note: hyphenated names become camelCased
});
_Layout.cshtml (optional, but good habit):
<body>
<!-- html content here. scripts go to bottom of body -->
#Scripts.Render("~/bundles/js")
#RenderSection("scripts", required: false)
</body>

There is no way to implement MVC / Razor code in JS files.
You should set variable data in your HTML (in the .cshtml files), and this is conceptually OK and does not violate separation of concerns (Server-generated HTML vs. client script code) because if you think about it, these variable values are a server concern.
Take a look at this (partial but nice) workaround: Using Inline C# inside Javascript File in MVC Framework

What you could do is passing the razor tags in as a variable.
In razor File>
var currency = '#Model.Currency';
doAlert(currency);
in JS file >
function doAlert(curr){
alert(curr);
}

Try JavaScriptModel ( http://jsm.codeplex.com ):
Just add the following code to your controller action:
this.AddJavaScriptVariable("Currency", Currency);
Now you can access the variable "Currency" in JavaScript.
If this variable should be available on the hole site, put it in a filter. An example how to use JavaScriptModel from a filter can be found in the documentation.

What i did was create a js object using the Method Invocation pattern, then you can call it from the external js file. As js uses global variables, i encapsulate it to ensure no conflicts from other js libraries.
Example:
In the view
#section scripts{
<script>
var thisPage = {
variableOne: '#Model.One',
someAjaxUrl: function () { return '#Url.Action("ActionName", "ControllerName")'; }
};
</script>
#Scripts.Render("~/Scripts/PathToExternalScriptFile.js")
}
Now inside of the external page you can then get the data with a protected scope to ensure that it does not conflict with other global variables in js.
console.log('VariableOne = ' + thisPage.variableOne);
console.log('Some URL = ' + thisPage.someAjaxUrl());
Also you can wrap it inside of a Module in the external file to even make it more clash proof.
Example:
$(function () {
MyHelperModule.init(thisPage || {});
});
var MyHelperModule = (function () {
var _helperName = 'MyHelperModule';
// default values
var _settings = { debug: false, timeout:10000, intervalRate:60000};
//initialize the module
var _init = function (settings) {
// combine/replace with (thisPage/settings) passed in
_settings = $.extend(_settings, settings);
// will only display if thisPage has a debug var set to true
_write('*** DEBUGGER ENABLED ***');
// do some setup stuff
// Example to set up interval
setInterval(
function () { _someCheck(); }
, _settings.intervalRate
);
return this; // allow for chaining of calls to helper
};
// sends info to console for module
var _write = function (text, always) {
if (always !== undefined && always === true || _settings.debug === true) {
console.log(moment(new Date()).format() + ' ~ ' + _helperName + ': ' + text);
}
};
// makes the request
var _someCheck = function () {
// if needed values are in settings
if (typeof _settings.someAjaxUrl === 'function'
&& _settings.variableOne !== undefined) {
$.ajax({
dataType: 'json'
, url: _settings.someAjaxUrl()
, data: {
varOne: _settings.variableOne
}
, timeout: _settings.timeout
}).done(function (data) {
// do stuff
_write('Done');
}).fail(function (jqxhr, textStatus, error) {
_write('Fail: [' + jqxhr.status + ']', true);
}).always(function () {
_write('Always');
});
} else {// if any of the page settings don't exist
_write('The module settings do not hold all required variables....', true);
}
};
// Public calls
return {
init: _init
};
})();

You could always try RazorJs. It's pretty much solves not being able to use a model in your js files RazorJs

I had the same problem and I did this:
View.
`var model = #Html.Raw(Json.Encode(Model.myModel));
myFunction(model);`
External js.
`function myFunction(model){
//do stuff
}`

Problem on how to update the DOM but do a check on the data with the code-behind

This is with ASP.NET Web Forms .NET 2.0 -
I have a situation that I am not sure how to fulfill all the requirements. I need to update an img source on the page if selections are made from a drop down on the same page.
Basically, the drop downs are 'options' for the item. If a selection is made (i.e. color: red) then I would update the img for the product to something like (productID_red.jpeg) IF one exists.
The problem is I don't want to do post backs and refresh the page every time a selection is made - especially if I do a check to see if the image exists before I swap out the img src for that product and the file doesn't exist so I just refreshed the entire page for nothing.
QUESTION:
So I have easily thrown some javascript together that formulates a string of the image file name based on the options selected. My question is, what options do I have to do the following:
submit the constructed image name (i.e. productID_red_large.jpg) to some where that will verify the file exists either in C# or if it is even possible in the javascript. I also have to check for different possible file types (i.e. .png, .jpg...etc.).
not do a post back and refresh the entire page
Any suggestions?

submit the constructed image name
(i.e. productID_red_large.jpg) to some
where that will verify the file exists
either in C# or if it is even possible
in the javascript. I also have to
check for different possible file
types (i.e. .png, .jpg...etc.).
not do a post back and refresh the
entire page
If you wish to not post back to the page you will want to look at $.ajax() or $.post() (which is just short hand for $.ajax() with some default options)
To handle that request you could use a Generic Http Handler.
A simple outline could work like the following:
jQuery example for the post:
$("someButton").click(function () {
//Get the image name
var imageToCheck = $("#imgFileName").val();
//construct the data to send to the handler
var dataToSend = {
fileName: imageToCheck
};
$.post("/somePath/ValidateImage.ashx", dataToSend, function (data) {
if (data === "valid") {
//Do something
} else {
//Handle error
}
}, "html");
})
Then on your asp.net side you would create an http handler that will validate that request.
public class Handler1 : IHttpHandler
{
public void ProcessRequest(HttpContext context)
{
var fileName = context.Request["fileName"];
var fullPath = Path.Combine("SomeLocalPath", fileName);
//Do something to validate the file
if (File.Exists(fullPath))
{
context.Response.Write("valid");
}
else
{
context.Response.Write("invalid");
}
}
public bool IsReusable
{
get
{
return false;
}
}
}
Hope this helps, if I missed the mark at all on this let me know and I can revise.

We have an app of the same type, webforms .net 2, we do something similar with the following setup:
Using jQuery you can call a method in the page behind of the current page, for example, the following will trigger the AJAX call when the select box called selectBoxName changes, so your code work out the image name here and send it to the server.
$(document).ready(function () {
$('#selectBoxName').change(function (event) {
var image_name = 'calculated image name';
$.ajax({
type: "POST",
url: 'SomePage.aspx/CheckImageName',
data: "{'imageName': '" + image_name + "'}",
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function (msg) {
alert(msg);
},
error: function (a, b, c) {
alert("The image could not be loaded.");
}
});
});
});
Where SomePage.aspx is the current page name, and image_name is filled with the name you have already worked out. You could replace the img src in the success and error messages, again using jQuery.
The code behind for that page would then have a method like the following, were you could just reutrn true/fase or the correct image path as a string if needed. You can even return more complex types/objects and it will automatically send back the proper JSON resposne.
[System.Web.Services.WebMethod(true)]
[System.Web.Script.Services.ScriptMethod(ResponseFormat = System.Web.Script.Services.ResponseFormat.Json)]
public static bool CheckImageName(string imageName)
{
/*
* Do some logic to check the file
if (file exists)
return true;
return false;
*/
}
As it is .net 2 app, you may need to install the AJAX Extensions:
http://www.microsoft.com/downloads/en/details.aspx?FamilyID=ca9d90fa-e8c9-42e3-aa19-08e2c027f5d6&displaylang=en

Could you not use a normal ajax call to the physical path of the image and check if it returns a 404?
Like this:
http://stackoverflow.com/questions/333634/http-head-request-in-javascript-ajax
<script type="text/javascript">
function UrlExists(url) {
var http = new XMLHttpRequest();
http.open('HEAD', url, false);
http.send();
return http.status != 404;
}
function ConstructImage() {
var e = document.getElementById("opt");
var url = '[yourpath]/' + e.value + '.jpg';
if (!UrlExists(url)) {
alert('doesnt exists');
//do stuff if doesnt exist
} else {
alert('exists');
//change img if it does
}
}
</script>
<select id="opt" onchange="ConstructImage()">
<option value="red">Red</option>
<option value="blue">Blue</option>
<option value="green">Green</option>
</select>