I've written some basic Javascript functions and would like to learn how to enable asynchronous postbacks within a C# 4.0/ASP.net project using this JS code.
For example, I have a script that increments a number when clicked. When clicked again, the number is decremented. I basically load the number from a database, then hide one <span> and show another with the corresponding decremented number on click. This is not complicated javascript; its a simple example. Now when I click the button I want to send this increment/decrement call back to the server to update the database's number.
I realize that I can accomplish something akin to this example using the AJAX Control Toolkit's toggle button. I, however, want to know how to use my OWN javascript to create AJAX functionality.
How do I accomplish this using C# and my custom Javascript code?
I'm not opposed to using the ASP.net AJAX library, I just don't want to use a ready built control. I want to learn the process of creating my own AJAX functionality. I would presume that I will have to use an asp:UpdatePanel, but I don't know how to call C# functions from the client side.
My javascript is not jQuery, in fact I want nothing to do with jQuery until I learn more about javascript and this process.
Simple with no UpdatePanel:
First, add a Generic Handler to your project (.ashx). This will act as our Http endpoint. Our javascript will call it. We could (and probably should), use a web service endpoint but that requires processing the response and complicates the example. A handler returns plain text.
<%# WebHandler Language="C#" Class="Handler" %>
using System;
using System.Web;
public class Handler : IHttpHandler
{
// We'll use a static var as our "database".
// Feel free to add real database calls to the increment
// and decrement actions below.
static int TheNumber = 0;
public void ProcessRequest(HttpContext context)
{
string action = context.Request.QueryString["action"];
if (!string.IsNullOrEmpty(action))
{
if (action == "increment")
TheNumber++; //database update and fetch goes here
else if (action == "decrement")
TheNumber--; //database update and fetch goes here
}
context.Response.ContentType = "text/plain";
context.Response.Write(TheNumber);
}
public bool IsReusable { get { return false; } }
}
Next, create your web page and add the async javascript.
<%# Page Language="C#"%>
<html>
<head runat="server">
<script type="text/javascript">
// An XMLHttpRequest object is required to make HTTP requests.
// Try a couple instantiation strategies to handle different
// browser implementations.
function createXMLHttpRequest() {
try { return new XMLHttpRequest(); } catch (e) { }
try { return new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) { }
try { return new ActiveXObject("Microsoft.XMLHTTP"); } catch (e) { }
alert("XMLHttpRequest not supported");
return null;
}
function callHandler(action) {
var xmlHttpReq = createXMLHttpRequest();
// We're interested in an asychronous request so we define a
// callback function to be called when the request is complete.
xmlHttpReq.onreadystatechange = function () {
if (xmlHttpReq.readyState == 4 && xmlHttpReq.status == 200)
document.getElementById("<%= lbl.ClientID%>").innerHTML
= xmlHttpReq.responseText;
}
xmlHttpReq.open("GET", "Handler.ashx?action=" + action, true);
xmlHttpReq.send(null);
}
</script>
</head>
<body>
<form id="Form1" runat="server">
<div>
The Number: <Label runat="server" id="lbl">0</Label>
</div>
<div>
<asp:Button ID="Button1" runat="server" Text="Increment"
OnClientClick="callHandler('increment');return false;" />
<asp:Button ID="Button2" runat="server" Text="Decrement"
OnClientClick="callHandler('decrement');return false;" />
</div>
</form>
</body>
</html>
The final flow is:
A web page user clicks the Increment or Decrement button which calls our javascript
Our javascript sends a request with the desired action in the querystring to Handler.ashx
Handler.ashx reads the querystring, increments or decrements its static variable, and returns the value
Our callback receives the value and updates our UI.
if your using an UpdatePanel it's very simple with a JavaScript call to __doPostBack. See here for example.
Have a look at this tutorial around AJAX
http://www.w3schools.com/Ajax/Default.Asp
It will give you an overview of using Javascript to GET and POST data using AJAX.
Hope this helps.
Here's a link on how you can incorporate ASP.NET C# with your custom Javascript code.
http://msdn.microsoft.com/en-us/library/bb386450.aspx
It also contains a sample VS 2010 project here:
http://go.microsoft.com/fwlink/?LinkId=185646
Here's generally what's going on here:
In the AjaxIScriptControl solution:
SampleTextBox.cs - takes care of rendering the script control on the page; and attachment to client javascript code (the js file)
SampleTextBox.js - takes care of client side functionality and generates Javascript object of control via prototype
Notes:
This example leverages existing
ASP.NET's built-in control (you
notice SampleTextBox inherits Textbox
and IScriptControl) but you can
render any type of HTML control if
you inherit ScriptControl class
instead.
This solution also chose to separated
the Script control code and website
code in two projects but you can
easily make it into one.
You can easily leverage another Javascript library in your JS file
In my experience so far, this is the one of the more elegant way to incorporate server side code with client side if you are to create re-useable controls for your website. You leverage server side power to do the initial rendering while provide client side capabilities through Javascript.
If you create your C# functions as WCF REST Services or older-style Script Services, then you can easily call your service methods from your JavaScript using a basic XmlHttpRequest (no jQuery or UpdatePanels needed).
Here's a quick jsFiddle I put together: http://jsfiddle.net/ndVeS/
This sample has two text boxes; you enter a value in the first one, click the button, and then that value is passed to a service (an echo service) and returned in the callback. The JavaScript code takes that value and populates the second textbox with it.
You could define a C# WCF RESTful service like this:
[ServiceContract]
public class EchoService : IEchoService {
[WebGet(UriTemplate="EchoMe?val={theValue}, ResponseFormat=WebMessageFormat.Json)]
public string EchoMe(string theValue) {
return theValue;
}
}
If you handle your calls this way, you can separate out your service logic from your presentation (ASPX files), and this allows for easier testing and you can also separate responsibilities from those who build the UI from those that build the business functionality.
I have to admit I'm more of a jQuery person when it comes to this, but I thought it's a great exercise to figure out how the XmlHttpRequest works under the hood. It makes you appreciate what jQuery (or similar framework) provides.
Here's a nice overview of the XmlHttpRequest object and how to use it: http://www.jibbering.com/2002/4/httprequest.html
I hope this helps.
function GetXmlHttpObject(handler) {
var objXMLHttp = null
if (window.XMLHttpRequest) {
objXMLHttp = new XMLHttpRequest()
}
else if (window.ActiveXObject) {
objXMLHttp = new ActiveXObject("Microsoft.XMLHTTP")
}
return objXMLHttp;
}
function GetDropDown() {
function stateChanged(StatesUpdated) {
if (xmlHttp.readyState == 4 || xmlHttp.readyState == "complete") {
document.getElementById('updateplace').innerHTML = xmlHttp.responseText;
//"updateplace" is you div id which will hold the new data or new page
if (navigator.appName != "Microsoft Internet Explorer") {
}
}
else {
//alert(xmlHttp.status);
}
}
xmlHttp = GetXmlHttpObject()
if (xmlHttp == null) {
alert("Browser does not support HTTP Request");
return;
}
url = "xyz.aspx" //this might be sent to any post data
url = url + "&sid=" + Math.random();
xmlHttp.onreadystatechange = stateChanged;
xmlHttp.open("GET", url, true);
xmlHttp.send(null);
}
with the above code you can send data to any .cs file also where you can change the data and load it in a new page which will load in the update div and the method should redirect to the new aspx file.
I hope you got the logic :)
if you have any doubts reach me # sankalpa.sam#gmail.com
I know it's not MVC that you're doing, but have a look at the MVC section of the ASP.NET site and you will find a lot of examples of AJAX calls there - MVC doesn't use those dreadful script-soup creating .NET objects. Most will probably be using jQuery - this is an open-source javascript library that can plug into any web app and provides some really nice functionality.
Maybe u r looking for this:
function ajaxscript(){
$.ajax({
type: "POST",
url: |url/methodName|,
data: |variable_name|,
contentType: "application/json; charset=utf-8",
dataType: "json",
success: |some javascript here|,
error: |some javascript here|
});
Related
Basically I am looking for a reliable log out mechanism when the user closes his tab. This includes calling some server code and thus all client side only mechanisms like deleting the cookie wont work for me.
On the internet you mostly find the approach to intercept the window.unload function and then place some code in there. I know there is the possibility to filter out normal navigation requests from other events that might trigger window.unload, but I generally don't like this approach, as I have to make some sort of synchronous AJAX call in order to reliable execute some custom logout code on the server, which is definitely not the best way of achieving what I want.
There is the second approach of implementing a Heartbeat function to periodically check if the client responds. I do think this is the best approach for me / my scenario, but I am actually struggling with the implementation with ASP.NET MVC.
How would I approach this in ASP.NET MVC? I already thought of SignalR, but it's actually not directly possible to access session information within the SignalR context.
It is easy to find some fancy implementations of this (see, for instance, this question).
For a basic heartbeat implementation you will need three files: the HTML (the website page sending the beats), the controller (receiving the beats) and the JavaScript file (with your heartbeat function). You may include the JavaScript code in the HTML file, but it's better practice to keep it separated.
Here you have the exact contents of my working example:
HTML file (Heart.cshtml)
Note that you need to include both the JavaScript file and jQuery. #Url.Action("ReceiveHeartbeat", "Auxiliary") gives the address to the method (ReceiveHeartbeat) in the controller (AuxiliaryController).
<head>
<script type="text/javascript" src="~/Scripts/heartBeat.js"></script>
<script src="https://code.jquery.com/jquery-1.11.3.min.js"></script>
</head>
<body>
<script type="text/javascript">
LaunchHeartBeat('#Url.Action("ReceiveHeartbeat", "Auxiliary")');
</script>
</body>
Javascript (heartBeat.js)
Other people use setTimeout, but if you want a loop using setTimeout is cleaner. I would recommend writing two functions, using setInterval(myFunction, myInterval); (see below). You can add more stuff to the Ajax request (for instance, a success: action).
function LaunchHeartBeat(actionUrl) {
var intervalMilliseconds = 750;
setInterval(function () {
$.ajax({
type: "POST",
url: actionUrl
});
}, intervalMilliseconds);
}
Controller (AuxiliaryController.cs)
[HttpPost]
public JsonResult KeepSessionAlive()
{
// You may do stuff here
return new JsonResult { Data = "success" };
}
Edit: The alternative syntax for the Javascript file:
var actionUrl = null;
var intervalMilliseconds = 1000;
function LaunchHeartBeat(myUrl) {
actionUrl = myUrl;
setInterval(HeartBeat, intervalMilliseconds);
}
function HeartBeat() {
$.ajax({
type: "POST",
url: actionUrl
});
}
During ASP.Net development i am often unsure weather i should be performing some functionality using an ajax request vs handling it all on the client with JavaScript. I often will want to use Jquery ajax functions in order to speed development up and improve maintainability even though i can achieve the same result without contacting the server.
Here is one example. In my MVC view i need to update a partial view in response to a button click. Here is a simplified version of my partial view
#foreach (Requestbox.Code.XmlContentField xmlControl in Model.RequestContentControls)
{
if (Model.IsInEditMode)
{
ViewContext.Writer.Write("<div class='editDiv'>
<a href='#' onclick='EditClick()'>Edit</a>
<a href='#' onclick='DeleteClick()'>Delete</a>");
}
switch (xmlControl.ControlType)
{
case "TextBoxField":
<div class="clearfix">
#Html.DevExpress().Label(settings => {
settings.Name = xmlControl.FieldName + "Label";
settings.AssociatedControlName = xmlControl.FieldName + "TextBox";
settings.Text = xmlControl.LabelText;
}).GetHtml()
<div class="input">
#Html.DevExpress().TextBox(settings => {
settings.Name = xmlControl.FieldName + "TextBox";
MvcExtensionHelpers.SetTextBoxSettings(settings);
settings.ControlStyle.CssClass += " full-width";
}).GetHtml()
</div>
</div>
break;
case "Header":
string header = string.Format("<{0}>{1}</{0}>", xmlControl.HeaderType,xmlControl.Value);
#Html.Raw(header)
break;
}
if (Model.IsInEditMode)
{
ViewContext.Writer.Write("</div>");
}
}
When the Edit button is clicked i need to wrap each of my sections in a div and add 2 anchor elements with onclick functions inside. I can do this by using an ajax post request and setting the Model with "IsInEditMode to true" here is the code i could call, which replaces the current partial view with the new one.
function EnableEditClick() {
$.post(rootDir + "Admin/EditClick",null,
function(partialViewResult){
$("#refTable").html(partialViewResult);
});
}
Here is the Action that could handle the ajax request
public ActionResult EditClick()
{
MyModel model = new MyModel();
model.IsInEditMode = true;
return PartialView("CustomRequest", model);
}
This is one solution, another would be to handle this all on the client by using jquery to select each of my elements that are needed and to insert the anchor elements directly. I would also be able to take some code out of the view. So something like this (Haven't tested this code but i hope you get the idea)
function EditClick()
{
var elements = $('.myTable .clearfix')
elemtns.append(' <a href='#' onclick='EditClick()'>Edit</a>
<a href='#' onclick='DeleteClick()'>Delete</a>');
}
I am torn on which will be better maintainability wise, as with the ajax way i don't have to write html in JavaScript pages and i think it will be clearer and more readable when revisting the code. However i am then using a unnecessary request to the server when i could it handle all on the client.
So my questions is should i always be doing everything on the client if possible even at the result of maintainability. Any feedback on my example is much appreciated as well.
I recommend you to use AJAX for operations, which require some background calculations on the server or to retrieve some DB data from the server. For GUI generation I would use JS, as it is quite quick, thanks to V8.
If you need to generate GUI by embedding some server data into it and this page has complex layout, I would use server side template engine.
In the example you've given, I would recommend the JS approach to control the availability of the edit and delete buttons. Or possibly a combination of the two.
When you make an Ajax call it creates a background request that causes some HTTP traffic. Unless there's some processing needed on the server to fulfil the request, then there is not much use sending that request to the server.
From looking at your code then the action you want to perform is to add two anchors to the page. This can be done easily with JS. You could even combine the two by including a partial view on your page that contains the elements you wish to include, wrapped in some markup to hide them.
You could create a partial view with the button markup.
<a href='#' onclick='EditClick()'>Edit</a>
<a href='#' onclick='DeleteClick()'>Delete</a>
And then include in your view.
<div id="buttons" style="display: none;">
#Html.Partial("_ButtonView")
</div>
Your JS would become.
function EditClick()
{
$("#buttons").toggle("display");
}
Check this JSFiddle for an example of what I mean.
In the context of this question, I would consider using an Ajax request for the actual edit action that returns a Json result with the action output. This would end up with something like.
$.ajax({ // ajax call starts
url: "YourArea/YourController/EditClick",
data: {"your data"},
dataType: 'json',
success: function(data) {
//handle json response
}
});
This Ajax request would call the controller code.
public JsonResult EditClick()
{
var myResult = Helper.Edit();
return Json(new { result = myResult });
}
Conclusion: If an event/action only affects what the user can see on the UI (i.e. controlling visibility and initiating animations) then you would probably only want to use JS/jQuery. If there's something more happening like server processing or fetching data from DB required then consider using Ajax.
In your example it seemed like the choice was between adding the elements dynamically to the page with JS or executing an Controller method via Ajax to get the elements as a partial view. I hope this answer provides a good solution for you.
I have a tricky problem. I am in a situation where I need to use a method defined in a .cs file from a javascript function. The problem is we are using .NET 1.1 and AJAX cannot be used for the application.
Also, I will need to pass a string from the javascript to the server side method. The page where I am implementing the javascript is a .as Any ideas?
I have tried doing a post back and creating a RaisePostBack event handler method (both in the .aspx page and the .ascx user control) but no luck.
It will be greatly appreciated if someone could help me out with the problem.
To be more precise. I have a class Attachment.cs which has a method Delete().
The javascript is called from a span's onclick event. The javascript function's input parameter would be a string which I will need to use to instantiate an Attachment.
I created a method which instantiates an Attachment using a string and calls the corresponding Delete() method for the Attachment object.
Now, I will need to pass the string from javascript function to the method I have created. I cannot use PageMethods.
The Javascript function is like:
// File ID is a string
function DeleteAtt(fileID)
{
//I tried PageMethods here, tried posting the page and getting the value through
// a RaisePostBack event etc. No luck.
}
The cs method I created is like:
public void DeleteAttachment(string ID)
{
Attachment obj = new Attachment(ID);
obj.Delete();
}
Do you mean that Microsoft's "ASP AJAX" is not an option, or do you mean that any jquery/any other library, or your own hand written javascript ajax won't work? ASP AJAX may not be supported by you version of .net, but surely simple javascript will still work, as you want to access the page from javascript.
If this is the case, something as simple as this, using jquery, would work:
function submit() {
$.post(
"pagename.aspx?string=" + variable,
function (data) {
alert("Response: " + data);
});
}
How about adding a callback-url as a query string to the url that you need to submit data to? Example:
Initial Page:(javascript)
function send(){
window.location = "submiturl.aspx?str=var&
callbackurl=http://www.myurl.com/page.aspx";
}
submiturl.aspx then catches both query strings [str] and [callbackurl], performs the action/function and then sends a response back to the [callbackurl]
response.redirect(callbackurl + "?response=" + data);
Initial Page now uses response.querystring to determine if it was succesful/whatever else you want and continues its business.
This definitely does not use ajax, and would be, by no means, asynchronous, but is based on a pretty lengthy history of API/callback & response design.
You can inject an invisible Iframe into the page and the SRC of the iframe can be used to pass data back to the server.
This is a very old technique back before jQuery and Prototype were invented.
See: http://www.ashleyit.com/rs/ for other alternatives.
I'm learning javacript, and I'm about at the point where I want to start doing some asychronous stuff. Here is the gist of my quest:
I have HTML code that looks like this:
<a id='nine' onclick="SendToServer('nine');">Nine</a>
I then want a way to, in Javascript, send back to the server that a#nine was clicked.
function SendToServer(id)
{
//Send that a#nine was clicked back to server
}
I then want some sort of handler function in c# to update an entry in a database.
public void GetMessageFromJSHandler(int id)
{
Item[x][y] = id;
}
I don't want the page to reload, I don't want anything to change on the page, and I want to do this in straight javascript so that I can learn how it works.
This is a GREAT resource: http://msdn.microsoft.com/en-us/library/ms178210.aspx I ended up altering this example for my needs. All Js and very straightforward.
Well, inside the context of your question, you're on the right track. You can use this example: http://www.devx.com/DevX/Tip/17500 to see how to populate your SendToServer function
GetMessageFromJSHandler would probably be called by the ProcessRequest method of an implementer of IHttpHandler, at least in the easiest scenario.
but that way of doing things is really for academic purposes, learning the plumbing as it were. In a production environment, you're much better off using a framework. My personal crack of choices is jquery on the client and ASP.NET MVC on the server, but if you like "regular" ASP.NET (aka webforms) then check out the MS Ajax libraries to see some easier ways of doign things in a scalable & maintainable fashion.
You can mark your page methods with a WebMethod attribute to create stubs for them on the client-side. Here is an example.
Another thing you could do is make your page method static and call it using jQuery's ajax() function. Here is how this way works.
jQuery:
function SendToServer(id)
{
$.ajax({
url: "/GetMessageFromJSHandler",
type: "POST",
data: { 'id': id }
}):
}
function SendToServer(id){
var pageUrl = "SamplePage.aspx?callback=true&ItemId=" +item
if (window.XMLHttpRequest)
{
var xmlRequest = new XMLHttpRequest();
}
else
{
var xmlRequest = new ActiveXObject("Microsoft.XMLHTTP");
}
xmlRequest.open("POST", pageUrl, false);
xmlRequest.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
xmlRequest.send(null);
}
On pageLoad you just check the callback flag and call your function
if(Request.QueryString["callback"].ToString() == "true")
{
string id = Request.QueryString["ItemId"].ToString()
GetMessageFromJSHandler(int id);
}
How do I access Jquery Treeview inside the .aspx file upon form submit?
also, Can I add nodes to Jquery Treeview on the fly? (on the client side)
I am using asp.net web forms, c#
EDITED:
someone mentioned the following in one of the questions:
"on form submit, someone is going to have to write code on the client to collect that data and send it via Ajax to a server method"
how is this done?????
Well, I think I've found what you want. Take a look here.
In brief, you must define a WebMethod on your server side, and then you can easily access it using jQuery. An exellent working example is under the link above, and here I'll modify it to show how you can pass arguments. So...
In your page code-behind *.cs:
// We'll use this class to communicate
public class Dog
{
public string Name { get; set; }
public string Color { get; set; }
}
// This is your page, in my case Default.aspx
public partial class _Default : System.Web.UI.Page
{
[WebMethod]
public static string ProcessData(Dog myDog)
{
return "Your " + myDog.Color + " dog's name is " + myDog.Name + "!";
}
}
Then on your *.aspx:
<script src="jquery-1.3.2.min.js" type="text/javascript"></script>
<script src="json2.js" type="text/javascript"></script>
<script type="text/javascript">
$(document).ready(function() {
$("#btnProcess").click(function() {
// This is what we want to send to the server
var dogItem =
{
Color: $("#txtColor").val(),
Name: $("#txtName").val()
};
// And this is how it should be sent - in serialized way
var dogItemSerialized = JSON.stringify(dogItem);
$.ajax({
type: "POST",
url: "Default.aspx/ProcessData",
data: "{'myDog':" + dogItemSerialized + "}",
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function(msg) {
$("#result").text(msg.d);
}
});
});
});
</script>
Color: <input id="txtColor" type="text" /><br />
Name: <input id="txtName" type="text" /><br />
<input id="btnProcess" type="button" value="Click Me" />
<div id="result"></div>
So here you fill textboxes and then your data is sent to the server which understands it as a Dog object. Pay attention to arguments passing, because this is the most confusing part. You should pass them in JSON format, which is a little bit "too-much-stringy". So I use here json2.js script which helps to convert usual javascript object into JSON-serialized string (JSON.stringify() method). It is available here. But it is still rather ugly =) It is important that I pass argument called "myDog" which value is the serialized dogItem. Because this is exactly what the server expects to get (so, for example, I can't change the argument name, this won't work:
data: "{'someAnotherArgumentName':" + dogItemSerialized + "}"
And the last thing. Pay attention to the following line:
success: function(msg) {
$("#result").text(msg.d);
}
If you are working with ASP.NET prior to 3.5 (for example, ASP.NET 2.0), then you'll need to write just $("#result").text(msg) instead of msg.d. Only ASP.NET 3.5 encapsulates all the data under "d" member for some reason...
Anyway, in the above article you can find useful links (both inside the article and in comments), so you can read more about arguments, "msg.d" and so on.
I hope this helps!
Since jQuery Treeview is a client-side component, you can't access it from the server-side. So in order to pass any data from your tree to the server, you have to write client-side javascript code (actually jQuery code). The same thing regarding adding nodes to the treeview on the fly: only using client-side jQuery code. Remember that your C# on the server-side has no idea about your TreeView.
The integration between jQuery and ASP.NET WebForms is rather problematic and "not so natural", because ASP.NET is built on different concept... So if you are working with ASP.NET WebForms, I would suggest you to use server-side components instead (it can be Microsoft's own ASP:TreeView or other 3rd-party WebForms-aimed components). Alternatively, you can try the new ASP.NET MVC Framework - it is built on more common (for other web-development platforms) concept, and the integration between it and jQuery is straightforward (actually jQuery is even shipped with it).
Don't get me wrong... I am not saying that the integration between jQuery and ASP.NET WebForms is totally impossible. It is possible. But you'll need to do "not-so-beautiful" things and work hard for every simple operation. If you still want to use jQuery, then use it only for the client-side animations...
UPDATE: As for this quote - "on form submit, someone is going to have to write code on the client to collect that data and send it via Ajax to a server method" - well, this is exactly what I am talking about. On the client-side you call javascript method when submitting the form (for example, by setting onclick='mymethod();' on your "Submit" button). This code does what it needs to do and then... it is supposed to perform AJAX call using jQuery nice syntax. But this won't work with ASP.NET WebForms, as I've explained before. Well, you can read about Microsoft AJAX Client-side library (here: http://msdn.microsoft.com/en-us/magazine/cc163300.aspx), perhaps this will help. But I still think that this integration won't be easy and straightforward. Use jQuery for the animation and ASP.NET server-side components for all other things!