hiddenfield - The value is not retained with Page.ClientScript.RegisterHiddenField in asp.net -

in asp.net c#, syntax:

 page.clientscript.registerhiddenfield("hffilename", value); 

i can define hiddenfield:

1) why in code , value nothing:

function pageload() {      alert(document.getelementbyid("hffilename").getattribute("value"));  } 

2) whats difference between hiddenfield , 1 can define asp.net toolbox:

<asp:hiddenfield id="hiddenfield1" runat="server" /> 

thank in advanced.

it working before, changed code in update panels , not working, possible of that?

try following:

on code behind:

protected void page_load(object sender, eventargs e)         {             page.clientscript.registerhiddenfield("hffilename", "testvalue");         } 

on jquery:

 $(document).ready(function () {             alert(document.getelementbyid("hffilename").getattribute("value"));         }) 

this working me.