the name clientscript does not exist in current context

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ASP.NET

Javascript

Hii friends...

i have written jquery for showing progressbar when clicking button in asp.net..code is working fine..i m calling this script from code behind as shown below.

string script = "$(document).ready(function () { $('[id*=btngenerate1]').click(); });";
        ClientScript.RegisterStartupScript(this.GetType(), "click", script, true);

but its giving me error message that' the name clientscript does not exist in current context'. i also written all jscript in scriptmanager tag in master page.

<asp:ScriptManager ID="ScriptManager1" runat="server">
        &lt;Scripts>
            <asp:ScriptReference Path="~/jquery/jquery-1.2.3.min.js" />
            <asp:ScriptReference Path="~/jquery/jqModal.js" />
            <asp:ScriptReference Path="~/jquery/coloranim.js" />
            <asp:ScriptReference Path="~/jquery/jquery.js" />

        &lt;/Scripts>
    </asp:ScriptManager>

please help me..
thanks in advance.