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Is there any javascript event which is triggered on postback?
If not, how can I run client side code immediately after or before a page postback?
683
How to Raise a Postback from JavaScript? To do this, we need to just call the __doPostBack() function from our javascript code. When the above function is called, it will raise a postback to server.
The __doPostBack function contains two arguments, eventTarget and eventArgument. The eventTarget is “Button2” and the eventArgument is “My Argument.” Later, in the C# code behind, I have accessed the eventArgument using the Request. Params collection. The passedArgument variable will contain the value “My Argument.”
A Postback Event is a string of information that is sent to a network's specific URL that contains information about the post-install event pertinent to the network.
You can use something like document. getElementById("__VIEWSTATE") or the jQuery equivalent. However, if you want to see whether the current page was generated in response to a postback, then you need to insert that data into the page on the server side first.
I believe what you are looking for is the Sys.WebForms.PageRequestManager beginRequest Event
Excerpt:
The beginRequest event is raised before the processing of an asynchronous postback starts and the postback is sent to the server. You can use this event to call custom script to set a request header or to start an animation that notifies the user that the postback is being processed.
Code Sample: (From the link)
<script type="text/javascript" language="javascript">
Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(BeginRequestHandler);
Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequestHandler);
function BeginRequestHandler(sender, args)
{
var elem = args.get_postBackElement();
ActivateAlertDiv('visible', 'AlertDiv', elem.value + ' processing...');
}
function EndRequestHandler(sender, args)
{
ActivateAlertDiv('hidden', 'AlertDiv', '');
}
function ActivateAlertDiv(visstring, elem, msg)
{
var adiv = $get(elem);
adiv.style.visibility = visstring;
adiv.innerHTML = msg;
}
</script>
I hope that helps. The PageRequestManager class seems to be little known about and little utilized.
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