How can I call a javascript function, that is in the aspx page, from the Page_Load method, in the code-behind?
The simple answer is, you can't. The code in the Page_Load method executes on the server, javascript executes on the client.
If what you want to do is add a call to a javascript method, in the Page_Load so that once the page is loaded by the browser, the javascript executes, then you can use the ScriptManager:
if (myConditionForAddingCallToJavascriptIsMet)
{
Page.ClientScript.RegisterClientScriptBlock(typeof(ScriptManager), "CallMyMethod", "myMethod();");
}
else
{
// Do something else, add a different block of javascript, or do nothing!
}
To use this, you'll need to have an <asp:ScriptManager> element in your markup for it to use (if memory serves, an exception will be thrown if you don't have one). The text "CallMyMethod" is used by the ScriptManager to uniquely identify the script that it injects for you, and the text "myMethod();" is embedded, so you'll end up with an additional script element in your page similar to this:
<script language="javascript" type="text/javascript">
myMethod();
</script>
The easiest way is to use the page's ClientScript property. You can register some code to run when the page loads using something like
ClientScript.RegisterStartupScript(GetType(), "hiya", "alert('hi!')", true);
See http://msdn.microsoft.com/en-us/library/asz8zsxy.aspx for more info.
This should be available from a child control by tacking "Page." onto the beginning of the code above.
Why would you want to do this?
What's the purpose?
Anyway you can do the following, but I DON'T recommend it!!! :
protected void Page_Load(object sender, EventArgs e)
{
string pagename = "Test.aspx";
String scriptString = "<script language=JavaScript> function DoClick() {";
scriptString += " window.showModalDialog('" + pagename + "' )}";
scriptString += "</script>";
if(!this.IsStartupScriptRegistered("Startup")) //This is **not** a good practice
this.RegisterStartupScript("Startup", scriptString);
}
Can you supply with more information of what you want to achieve to get better answer..
Shide's solution works. The problem is if you want to run your piece of code only on postback, for example. The solution I found was to use a "cookie": I verify if cookie x exists, if it doesn't I run the javascript code and set the cookie. When you hit refresh, the cookie will be found so the piece of code won't run.
function pageLoad() {
if(localStorage.getItem("cookie") === null) {
localStorage.setItem("cookie", true);
//run code
}
}
Any code you need to run every single time just leave it out of the if statement.
You need to use Register client Script:
MSDN
CodeProject
I do it in a Page Load method:
if (!this.ClientScript.IsClientScriptBlockRegistered(this.GetType(), "HelpScript"))
{
var scriptSource = "function ShowHelp() { alert(""); };\n";
ScriptManager.RegisterClientScriptBlock(Page, this.GetType(), "HelpScript", scriptSource, true);
}
but I don't think it's recommended
I mean... you can do this, and it'll work. But for me the only good reason of inserting a script from asp.net page is to get some client side features of server controls.
So for example to get an instance of control:
var myControlId = this.control.ClientID;
But writing entire javascript functions and logic on the server side is not comfortable when you need to change it or debug it (for me it's hardcoded string).
If you just want to call a JavaScript function ( and do not need to pass something from code-behind, then use this...)
document.onload = function () { your-function(); };
window.onload = function () { your-function(); };
document.readyState = function () { your-function(); }
... depending on your specific requirements.
Hope this makes sense to you & answers your question.
this is a little trick i found myself without having server side code .
that function will be called when the page loads (can be used with an update panel) :
<script>
function pageLoad() {
//Do your stuff
}
</script>
it is unknown and yet works like a charm
Please try this code:
ScriptManager.RegisterClientScriptBlock(this.Page, this.GetType(), "MyFun1", "test();", true);
Related
I'm having some issues accessing a static variable in a class when getting it from a code behind function called from javascript.
My aspx page:
<script type="text/javascript">
function AlertMsg(msg) {
var msg213 = "<%= GetValue(" msg ") %>";
alert(msg + '::' + msg213);
}
</script>
Code behind:
public string GetValue(string sString)
{
return MyNamespace.MyClass.MyStaticVariable;
}
I set this variable in a page_load in another page. I'm accessing the javascript function by invoking it from a C# WebBrowser application. It's always empty.
Any ideas?
I think you just need to add '+' around your reference to 'msg'
var msg213 = "<%= GetValue(" + msg + ") %>";
ASP.NET isn't like a desktop application, any variables written on another page will be lost when moving to another page. You need to save the value to somewhere persistent.
Session
Cache
Database
App or Web Config files.
Variable needs to be a const or static
Try this
'<%= GetValue("Some Value") %>';
This means when page rendering, GetValue method calls and return string will be write in the document body, like Respose.Write
This will only happend when when page rendering and no further call will happend.
I think part of the confusion is coming from the formatting in the code. If you look at just the server tag: <%= GetValue(" msg ") %>, you will see that the GetValue method is being invoked, and the literal string msg is being passed in. There are quotes around the server tag itself, but those do not affect what is inside the server tag. You are not passing in the value of the msg parameter of the JavaScript function.
Server methods cannot be invoked from JavaScript in such a simple manner, it requires using something like AJAX to accomplish.
I am using prototype, and i have a function as follows:
MyJSClass.prototype.AddLetters = function()
{
}
I would like to call this from c# based on some conditions i need to evaluate on pre-render.
Hello you can try with this code
ClientScriptManager cs = Page.ClientScript;
String yourScript= "function();";
cs.RegisterStartupScript(this.GetType(), "key script", yourScript, true);
Since you can't directly call JavaScript code from C# - especially before the page is rendered, you need a way of:
communicating the requirement/condition to the JavaScript code
picking up and appropriately dealing with the requirement/condition at the right time.
For 1. I recommend using the ClientScriptManager to insert/modify a variable, although there are other options below.
For 2. you should probably add some javascript which will pick up the communication.
Options for 1.:
Add a field into the page
Add a script into the page (e.g. using the Client ScriptManager) which will set a variable
Inject the script into the page directly at the relevant point for it to run
set a flag in the C# which you then check when you receive an AJAX call (which you might use if it will change according to server-side rules while the page is open...)
So this seems famous, but with little different.
JavaScript Function:
function ShowMessage(Message, Title, isAlarm) {
$("#dtext").html(Message);
$("span.ui-dialog-title").text(Title);
$("#dialog").dialog({
open: function(e) {
var Dia = $(e.target);
if (isAlarm == true) {
Dia.parents(".ui-dialog:first").find(".ui-dialog-titlebar").css("background", "red");
Dia.parents(".ui-dialog:first").find(".ui-dialog-titlebar").css("color", "White");
}
else {
Dia.parents(".ui-dialog:first").find(".ui-dialog-titlebar").css("background", "LightSeaGreen");
Dia.parents(".ui-dialog:first").find(".ui-dialog-titlebar").css("color", "White");
}
},
show: "blind",
hide: "clip",
modal: true,
resizable: false,
buttons: {
"Close": function(e) {
$(this).dialog("close");
return true;
}
}
});
}
As you see this method fill with Jquery-Code. if this is just java-script, We can use this Code to call that function but in this case this method don't work well.
C# calling JS Method:
if (!Pointer.ClientScript.IsStartupScriptRegistered("message"))
Pointer.Page.ClientScript.RegisterStartupScript
(Pointer.Master.GetType(), "message", "ShowMessage('messageBox','" + Message + "',false);", true);
I don't Know how to resolve this problem. I Want just call this Js function from server-side?
Edit 1
Thank for your attention. some guy's want from me describe my problem better. Why I can't ?
Cuz I don't know what's exactly problem.
I just can say, I test this program with FireBug and set break-point on first line on JS function but in run time when I call that Js function that break-point Hit for a few Millisecond and then page reload goes complete and nothing happened.
I'm newbie on JS and jQuery. So Instead hitting down vote plz try sample program with these Code's and help Me.
thank Again (specially Stefan, PirateKitten, Widor)
Edit 2
I made this Function(JQuery Message Function) to replace Old Function which only use simple JS alert. and I must say old version work(even if I call that from server-side with JS-Caller-Function I write).
in this case, even if I call new Function(JQ Function) with Js in page like :
<button type="button" onclick="ShowMessage('hi','title',false)">
Display Message
</button>
It's worked, But when call that from server side, Function don't work.
Put simply; you can't.
JavaScript runs clientside, C# runs serverside.
However, you can generate JavaScript serverside and output it to the client.
See my answer here: Call javascript from vb.net code behind
Code that is registered with Page.ClientScript.RegisterStartupScript is "rendered" at the end of the page. To be exact in a script tag before the form close tag. However, the code might run before the DOM tree is fully generated.
Since your ShowMessage function access the DOM tree your issue could be related to missing DOM tree elements.
If I do interpret your question correctly there are no JS erros on the page. This chould be as a result of the jquery selector behavior:
$("#dtext").html(Message);
This will set the HTML of all elements with the id dtext. Since there might be no elements with the ID dtext yet, $("#dtext") will return an empty collection and no actions are taken.
To workaround this issue you can try to run your code in the the jquery document ready event. jQuery fires this event if the page was fully loaded:
$(document).ready(function() { ShowMessage('messageBox','" + Message + "', false); }
ServerCode:
if (!Pointer.ClientScript.IsStartupScriptRegistered("message"))
Pointer.Page.ClientScript.RegisterStartupScript
(Pointer.Master.GetType(), "message", "$(document).ready(function() {ShowMessage('messageBox','" + Message + "',false); }", true);
you can call js function from server side like this
Page.ClientScript.RegisterStartupScript(this.GetType(), "show", "ShowMessage()",true);
Hope this would help 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'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|
});