I have tried "every" possible way of sending the screen.width vlaue from the JS script on the aspx page to the c# in the code behind and while I can see the screen.width being assigned correctly it never gets assigned to my hidden field value.

<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">

   <asp:HiddenField ID="hiddenfield" runat="server" />

   <script type="text/javascript" language="javascript">
       $(function(){ 
       $('#hiddenfield').val(screen.width); 
    });
    </script>

other content

</asp:Content>

and the code behind:

protected void btnChartGo_Click(object sender, EventArgs e)
{
   string s = hiddenfield.Value;
}

No matter what I try s is always ""

Something wrong with the above, everyone seems to be doing it like that and it works?

I have tried "every" possible way of sending the screen.width vlaue from the JS script on the aspx page to the c# in the code behind and while I can see the screen.width being assigned correctly it never gets assigned to my hidden field value.

<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">

   <asp:HiddenField ID="hiddenfield" runat="server" />

   <script type="text/javascript" language="javascript">
       $(function(){ 
       $('#hiddenfield').val(screen.width); 
    });
    </script>

other content

</asp:Content>

and the code behind:

protected void btnChartGo_Click(object sender, EventArgs e)
{
   string s = hiddenfield.Value;
}

No matter what I try s is always ""

Something wrong with the above, everyone seems to be doing it like that and it works?

• c#
• javascript
• jquery
• asp
• code-behind

Share Improve this question Follow asked Jun 20, 2012 at 8:12 user1468537user1468537 70355 gold badges1313 silver badges2727 bronze badges

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4 Answers 4

Sorted by: Reset to default 2

The ID of the rendered hidden field isn't "hiddenfield" - it'll be something like ctl00_bodycontent_hiddenfield.

Try using

$('[id$="hiddenfield"]') 

as the selector instead.

<asp:HiddenField ID="hiddenfield" runat="server" ClientIDMode="Static">
</asp:HiddenField >

Make sure client ID mode of your hidden field is static if you are using ASP.NET 4 or use

$('#<%= hiddenfield.ClientID %>').val(screen.width); 

This should get the right selector:

$('#<%= hiddenfield.ClientID %>').val(screen.width); 

Check the view source of the page and find out proper id of the element and then use jquery selector over it and then at the page load check for request.form collection to check if hidden variable is ing in post request or not