How to access hidden field from usercontrol

I have a hidden variable in my aspx page i.e mainpage.aspx

<asp:HiddenField runat="server" id="hdnCommonvCode" />

mainpage.aspx contains开发者_如何学JAVA tabcontainer control. On each tab an usercontrol is added. If i try to access this hidden field alert($find("<%=hdnCommonvasCode.ClientID %>")); from usercontrol it shows compiler error msg

Compiler Error Message: CS0103: The name 'hdnCommonvCode' does not exist in the current context

Did you tried like this var hidx = document.getElementById('hdnCommonvCode');