variable session

var strTest=document.getElementById('DropDownList1').value;
<%Session["Test"] = "'+ strTest +'";%>
var session_value='<%=Session["Test"]%>';
alert(session_value);
It is Working fine in Client Side. But i Server Side(Code Behind), the Session["Test"] value is
'+ strTest +'.
Is any other way to assign values to Session in client side and read the  the new value in server side?

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