My server-side ASP.NET code generates a JS function (actual function, e.g. function Foo() {...}) on initial page load using ClientScript.RegisterStartupScript. That function becomes part of ASPX markup and executes when client calls it.
The problem is: I need to modify that function's code in server-side partial postback (Update panel). But when I generate the function with the same name function Foo() {...} via ScriptManager.RegisterStartupScript it doesn't seem to take effect - original function generated in PageLoad's ClientScript.RegisterStartupScript is called.
Is there any way to regenerate client-side function in partial postback after it had been generated on initial page load?
Thanks!
Answered in my first comment to the question.
Related
I have a custom control (ascx) which implements the IPostBackEventHandler interface for intercepting custom events triggered by custom rendered HTML links.
In this control I use an update panel and inside the update panel I use a literal control in which I render custom HTML links.
When I render the HTML links inside the literal control I use a StringBuilder with the following code:
sb.AppendFormat ("Text",
this.Page.ClientScript.GetPostBackClientHyperlink(this, custom_string_param));
Hyperlinks are rendered fine, and when clicking on them an asynchronous postback is triggered and a partial update is fired (since all links are rendered inside the Update panel).
The problem is that I need to do some custom Javascript before firing the __doPostBack which is rendered with the above code. So here is a simplified version of the changed code:
sb.AppendFormat ("Text",
custom_string_param);
Also in the ascx markup I use the following code (inside or outside the Update panel):
<script language="javascript" type="text/javascript">
function JSFunc(param) {
// custom js code here ....
__doPostBack('<%=this.ClientID%>', param);
}
</script>
The problem here is that when a link is clicked it performs a full postback and not a partial one. I also tested more simple versions of the above code and it seems that if you remove the __doPostBack from the href or the onclick events from the link ( tag) and move it to a custom js function which in turns you supply to the link, a full postback is triggered.
Note that there is no error on the page and in both cases the code work correctly. The page is rendering correctly depending on the parameters returned from the __doPostBack, but in the second case a full instead of partial postback is firing.
Any ideas?
Thanks in advance,
George
I think you can't call __doPostBack with the ClientID. It actually uses UniqueIDWithDollars, but generally with ASP.NET Web Forms I say: you don't want to know.
Since calling this method is all about abstracting away the details of how post back works, you would be better off asking the framework for the code. Luckily, there's a special method just for that, which will take care of the details. In your code it would look like something like this:
<script language="javascript" type="text/javascript">
function JSFunc(param) {
// custom js code here ....
<%= Page.ClientScript.GetPostBackEventReference(this, custom_string_param) %>
}
</script>
This let's the client script manager create the piece of JavaScript code, using a reference to your user control (this) and any custom event argument (custom_string_param).
There's one caveat though. When calling it this way, it will add javascript: to the beginning of the string.
To override this behaviour, you need to use an overload of GetPostBackEventReference that accepts an instance of PostBackOptions as its first argument, the instance having its RequiresJavaScriptProtocol property set to false.
PostBackOptions options = new PostBackOptions(this, custom_string_param)
options.RequiresJavaScriptProtocol = false;
Page.ClientScript.GetPostBackEventReference(options)
Hi
I am just wondering why some people suggest RegisterStartupScript() to call client side js while some suggests RegisterClientScriptBlock().
Please make me clear whats the difference between the two as they doing the same operations, for using js statement calls and which one is preferable if I only use js statements like alert, return confirm from codebehind.
The RegisterClientScriptBlock method inserts the client-side script immediately below the opening tag of the Page object's <form runat="server"> element. The code cannot access any of the form's elements because, at that time, the elements haven't been instantiated yet.
The RegisterStartupScript method inserts the specified client-side script just before the closing tag of the Page object's <form runat="server"> element. The code can access any of the form's elements because, at that time, the elements have been instantiated. The choice of which method to use really depends on the "order" in which you want your script to be run by the browser when rendering the page.
Normally you would use RegisterClientScriptBlock if you want to register js-functions and use RegisterStartupScript if you want to call these functions or want to access controls on your page.
For further informations have a look at MSDN.
I render HTML returned from an ajax call and currently uses simple html controls and the string that is returned from the ajax call looks like this:
string s = "<tr><td>MyLink</td></tr>";
Now, on the click on these links I need to do some processing on the server side to determine where I need to navigate to and for other information. My understanding is that I cannot use <asp:linkbutton /> in this html string I am building.
How do I make a server side call if i don't want to use ajax.
You don't necessarily need to use ASP .NET server controls to enact server-side logic in a post-back. The link for which you manually build the HTML and return in the AJAX call can direct the user to an HttpHandler (or even an aspx page) and pass necessary values to that handler/page on the query string. Then that handler/page can perform its server-side logic and redirect as necessary.
Maybe I've misunderstood the problem? Is there a specific reason why you're looking to use a LinkButton in particular?
Write a javascript function and call it from each link's onlick like this:
My Link
someFunc can then set a hidden input field to the value you want the server to react to. This could be anything from the link element (the text of the link, the value of an attribute you specify in your AJAX response, etc.). At the end of the function, call form1.submit();
function someFunc(link){
var hiddenInput = document.getElementById("ClickedLink");
hiddenInput.value = link.innerText;
form1.submit();
}
Then on the server, in your On_Load in the code behind:
if(ClickedLink.Value != ""){
ProcessLinkClick(ClickedLink.Value);
}
I like to call a JavaScript function from c#. Can any one can give me code snippet.
More detail...
I have a asp.net page which has a asp button. when i click that button, i like to call javascript function.
like wise....
in my asp.net page,
<button id="save" onclick="i like to call a method resides in asp.net page'>Save</button>
More and more details...
when click the asp.net button, i like to perform some server side action and then like to call a javascript function from there itself...
For an asp:button you use OnClientClick
<asp:Button id="myid" runat="server" OnClientClick="alert('test')" />
On the assumption that you're coding in ASP.NET (including MVC), calling a JavaScript function would mean embedding the call in JavaScript into your ASPX code, like so:
<script type="text/javascript">
doSomething();
</script>
You do have the opportunity to pass information from your C# to the JS call, just as you would have any other code alter the results of your ASPX:
<script type="text/javascript">
doSomething("<%= GetSomeTextFromCSharp(); %>");
</script>
This is really stretching the definition of "calling JavaScript from C#" though. What you're doing is having your C#/ASPX code generate HTML/JavaScript, which the browser then interprets as it would any other HTML/JS (regardless of how it was generated).
Perhaps you could explain what you're trying to do a bit more.
i tried with this code it works for me check whether it helps
1)
Page.ClientScript.RegisterStartupScript(this.GetType(), "click", "alert('Informations');", true);
The other way is call the javascript method which is written in source page
Page.ClientScript.RegisterStartupScript(this.GetType(), "click", "xyz();", true);
You can't "call" a Javascript function from ASP.NET C# code-behind. You can write additional Javascript to the webpage. By the time the page is sent back to the user and the Javascript exists, your code-behind is gone. You can write out to a Literal or do a Response.Write()
Response.Write("<script language='javascript'>alert('Hellow World');</script>");
Sarathi, based on your recent update, it's not clear that you need any C# interaction at all. Your <button> appears to be strictly client-side (ie: HTML) with no ASP.NET interaction within it. To call your JavaScript function you'd attach the function call to the onclick attribute of the button tag:
<button id="save" onclick="mySaveFunction();'>Save</button>
Note that mySaveFunction() just needs to be defined in the browser's load stack for the current page. That means it could be defined in any of:
The ASPX page that holds the <button>
The Master page for the current ASPX page
One of the User controls (or MVC partials) loaded by the current ASPX page
An external JavaScript file that's loaded by one of the above.
Lastly, I'd just like to reiterate that there's nothing particularly C#/ASP.NET-specific about this. You could do the same with any language/framework, including static HTML files. Your question appears to be entirely JavaScript-dependent.
For the window object:
http://msdn.microsoft.com/en-us/library/ms536420%28VS.85%29.aspx
window.execScript
For the page pbject:
http://msdn.microsoft.com/en-us/library/dfbt9et1%28v=VS.71%29.aspx
RegisterClientScriptBlock
RegisterOnSubmitStatement
RegisterStartupScript
etc ...
you can call javascript function from code behind page ..for example you have closewindow function definition part in javasript..if you want to execute that function,you can write following codings in any click event in code behind page..
ClientScript.RegisterClientScriptBlock(GetType(), "close", "<script language=javascript>Closewindow();</script>", false);
I have an external javascript on my page, e.g. something like:
<script src="http://foo.com/script.js" type="text/javascript"></script>
and an UpdatePanel somewhere. The script writes some content, and does this from within an anonymous javascript function in the js file. I.e., there is something like this in the script:
(function(){document.write('content');})();
Whenever the UpdatePanel is updated through asynchronous postback, everything the script did (or any javascript on my page, for that matter) is made undone.
For normal javascript, I would just use:
Sys.WebForms.PageRequestManager.getInstance().add_endRequest(myFunction)
to redo all that, but since the function in the script source file is anonymous and called upon definition, I'm SOL! Any ideas?
Note: the external js source is from another domain and its content is out of my control.
Try this
private string _myScript = #"(function (){
var ys = document.createElement('script');
ys.type='text/javascript'; ys.async=true;
ys.src='http://foo.com/script.js';
var s = document.getElementsByTagName('script')[0];
s.parentNode.insertBefore(ys,s);
});";
Then in your Page_Load
ScriptManager.RegisterStartupScript(this.Page, this.Page.GetType(), "myScript", _myScript , true);
Ok, the "solution" ("dirty ugly hack", if you prefer) I came up with:
Instead of loading the js file directly, I load it via a wrapper that reads the file, wraps the result in custom javascript that puts the anonymous function in a global array, and call all functions in said array upon load and after each asynchronous postback.
Please don't enter this solutions in any beauty pageants.
The real problem here was that I wasn't using UpdatePanels correctly. If the UpdateMode of all the UpdatePanels on your page are set to Conditional, and your ScriptManager has partial updating enabled, it really shouldn't "[undo] everything the script did".