javascript - Get HTML inner HTML in C# when element not runat="server" -

i have html span contains number.

the span has value set javascript, not runat="server"

i need value contained in span, , store in c# string.

this proving more difficult expected.

i able alert box displays value doing following:

clientscript.registerstartupscript(gettype(), "ir", "settimeout(function(){alert(document.getelementbyid(\"loaninterestrate\").innerhtml);}, 3000)", true); 

but cannot see how return value c# code.

i know because clientscript.registerstartupscript returns void, there way of setting return value this?

or there way of getting html element.

i know can use hidden server side div, not suit purposes.

i need way obtain value of html span using c#.

any ideas, have been trying while , not got anywhere, , think is useful thing do.

you cannot create "real" runat=server element/control without doing full postback server.

the best approach may write script stores innerhtml asp.net hidden field right before submit page.